Modern strategies for torrent control: slit and w-weir check dams

Determinazione della distribuzione granulometrica del suolo mediante diffrattometria laser

Field Testing of a Simple Flume (SMBF) for Flow Measurement in Open Channels

In this paper the stage–discharge relationship of a new flume named SMBF (Samani, Magallanex, Baiamonte, Ferro), originally proposed by Samani and Magallanez and tested by Baiamonte and Ferro, for measuring flow discharge in open channels is reviewed. The flume is obtained inserting two semicylinders in a rectangular cross section. The results of some experimental runs carried out using horizontal flumes characterized by different values of the contraction ratio (ranging from 0.17 to 0.81) are used for determining the two coefficients of the power stage–discharge equation. The stage–discharge equation is tested using flow measurements carried out in the period between December 2004 and Marc…

Evaluating the Effects of the Rill Longitudinal Profile on Flow Resistance Law

In this paper, for the first time, the effect of the longitudinal profile shape of the rill (uniform, concave, and convex) on flow resistance law was studied. The first part of the paper is based on a theoretical equation to estimate the Darcy–Weisbach friction factor f, deduced from the power velocity distribution and rill measurements performed on a plot. At first, the equation to estimate the Γ parameter of the velocity profile was calibrated using all available measurements. Then an analysis of the hydraulic characteristics at reach scale, for comparable values of discharge, was carried out, comparing the different profile shapes. To assess the influence of the rill profile …

New-stage discharge relationships for free and submerged sluice gates

Abstract The flow movement through a sluice gate is investigated for both free and submerged flow conditions. For free flow condition, the current dimensionless formula, indicated acceptable accuracy; while for submerged flow condition it was modified especially for low submerged condition. In this regard, Buckingham theorem along with the Incomplete Self-Similarity concept was employed and a new stage–discharge relationship was developed accordingly. Also, to achieve a suitable formula for submerged flow condition being accurate in low submergence, the maximum tailwater depth allowing the free flow condition and head loss factor were identified as missing parameters in the functional dimen…

Testing a distributed approach for modelling sediment delivery

Abstract Both the theoretical basis of a distributed approach to sediment delivery and its agreement with basin sediment yield measurements are tested. At first, by using morphological data of five Apulian and four Calabrian basins, the applicability of a theoretically-based relationship for evaluating the sediment delivery ratio of each morphological unit SDR h, into which a basin is divided, is verified. Using the morphological data of the nine investigated basins, the sediment delivery relationship, i.e. the relationship of the basin sediment delivery ratio SDR Wand SDR h, is tested. The analysis showed that the relationships, proposed by Ferro (1997), establishing the dependence of the …

Flow Resistance Law in Channels with Flexible Submerged Vegetation

In this paper, experimental data collected in a straight flume having a bed covered by grasslike vegetation have been used to analyze flow resistance for flexible submerged elements. At first, the measurements are used to test the applicability of Kouwen’s method. Then, a calibration of two coefficients appearing in the semilogarithmic flow resistance equation is carried out. Finally, applying the P-theorem and the incomplete self-similarity condition, a flow resistance equation linking the friction factor with the shear Reynolds number, the depth-vegetation height ratio and the inflection degree is deduced.

Verifiche sperimentali della USLE a scala di bacino in Sicilia

Erosione e conservazione del suolo

Analisi dell’intensità della turbolenza di correnti in moto in alvei in ghiaia

Experimental Study of the Stage-Discharge Relationship for an Upstream Inclined Grid with Longitudinal Bars

AbstractIn this paper, the outflow process of an upstream inclined grid with longitudinal bars is studied by using the dimensional analysis and the incomplete self-similarity theory. Next, the theoretical analysis shows that a power equation can be used for establishing the stage-discharge equation. The coefficient and an exponent of the power equation depend on the slope angle and the void ratio. Finally, this new stage discharge is tested by using measurements obtained by laboratory runs conducted in this investigation.

Scour on Alluvial Bed Downstream of Grade-Control Structures

This paper describes an approach for predicting local scour downstream of grade control structures. The developed analysis applies the incomplete self-similarity (ISS) theory for deducing some physically based dimensionless groups controlling the geometrical pattern of the scour profile. The scour measurements available in the literature in conjunction with numerous unpublished data allow a multiregressive calibration of the ISS relationships. The experimental sample includes different bed grain-size distributions and scales of the erosive phenomenon. The results prove that the ratio between the upstream water head and the weir height is able to explain the measurements of scour depth carri…

Valutazione delle resistenze al moto per una corrente overland in presenza di trasporto solido

Testing the use of an image-based technique to measure gully erosion at Sparacia experimental area

The first part of this investigation was aimed at testing the use of a three‐dimensional (3D) digital terrain model and a quasi‐tridimensional (2.5D) digital elevation model obtained by a large series of oblique images of eroded channels taken from consumer un‐calibrated and non‐metric cameras. For two closed earth channels having a different sinuosity, the ground measurement of some cross sections by a profilometer (P) was carried out and their real volume was also measured. The comparison among the three methods (3D, 2.5D, and P) pointed out that a limited underestimation of the total volume always occurs and that the 3D method is characterized by the minimum difference between measured a…

Estimation of Evapotranspiration by Hargreaves Formula and Remotely Sensed Data in Semi-arid Mediterranean Areas

Abstract A methodology is proposed for estimating evapotranspiration by Hargreaves formula and image analysis of remotely sensed data. At first, for a large sicilian basin (Belice basin), theactualevapotranspiration values are estimated by the energy balance equation, spectral data of two Landsat TM images and ground agrometereological measurements. Then theseactualevapotranspiration estimates and thereferenceevapotranspiration values obtained by a slightly modified Hargreaves formula, which incorporates the outgoing short-wave radiation and an albedo coefficient equal to 0·23, are used for calculating suitable crop coefficients. Finally, the minimum area of each land-use map unit, obtained…

UTILIZACIÓN DE TÉCNICAS DE FOTO-RECONSTRUCCIÓN 3D AUTOMATIZADA EN GEOMORFOLOGÍA: EJEMPLOS PARA DIFERENTES MORFOLOGÍAS Y ESCALAS

Three-dimensional photo-reconstruction methods based on Structure from Motion (SfM) and MultiView-Stereo techniques (MVS) are tested for measuring, monitoring and quantifying three different geomorphological features: i) the Corral del Veleta rock glacier and ii) five small gully headcuts in Spain and iii) Calanchi type badland in Italy. Results about the accuracy, usefulness and applicability of these techniques are presented here. The results of these analyses showed centimeter-level accuracies with average distances to the benchmark models ranging from 0.009 m to 0.42 m.

Generalised stage-discharge relationship for rectangular weirs

Rectangular weirs, which are very common hydraulic structures used in irrigation channels as water measuring devices, can be used for measuring very small discharges as well as high flow rates. From the practical point of view the availability of a unique stage-discharge formula that can be applied for the different types of the rectangular weirs would be of great practical importance. At first, in this paper the Buckingham’s Theorem of the dimensional analysis and the self-similarity theory are used to deduce the stage-discharge curve of different kinds of rectangular weirs such as slit and partially contracted ones. Then the proposed formula is calibrated using both the experimental data …

18. Monitoraggio, Previsione e Controllo dell’Erosione Idrica

assente - capitolo di libro

Capturing gypsum rillenkarren morphometry by a 3D-photo reconstruction (3D-PR) technique

Abstract Rillenkarren are small scale, straight, narrow solution channels that head at the crest of a bare rock slope and are extinguished downslope. In this paper the applicability of 3D-photo reconstruction technique of the rock surface is proposed for capturing the rillenkarren morphometry on gypsum. At first, the measurements are used to assess a relationship between the width/depth ratio and the depth of the rillenkarren. The exponent of this power relationship resulted different from the theoretical value - 0.5, confirming that the cross-section profiles of a rillenkarren can have a shape different from parabolic. The analysis developed for the cross-section area, the perimeter and th…

The influence of roughness geometry and shields parameter on flow resistance in gravel-bed channels

The spatial variability of bed particles of a gravel-bed channel is analysed and treated experimentally in order to simulate the effects of the arrangement of coarse bed elements on the flow resistance law. For the studied bed patterns, characterized by the concentration Γ of coarser elements arranged on the bed layer, a particle arrangement parameter α is proposed. The α parameter is useful for estimating the intercept b0 of the semi-logarithmic flow resistance law deduced by flume measurements carried out for the hydraulic condition of large-scale and transition roughness. The differences between the experimental friction factor parameter values and the ones calculated by the proposed sem…

Opere in legname ed alterazioni biotiche del materiale ligneo

A comparative study of rainfall erosivity estimation for southern Italy and southeastern Australia

Abstract In this paper, using Sicilian and Australian rainfall intensity data, a comparison between different estimators (modified Fournier index F, FF index) of the rainfall erosivity factor in the USLE was made. The relationship between the modified Fournier index and the mean annual rainfall, P, was theoretically derived. The K constant, linking the FF index and P, and its cumulative distribution function (CDF) were used to establish hydrological similitude among different geographical regions of southern Italy and southeastern Australia. To predict the erosion risk for an event of given average recurrence interval, the probability distribution of the annual value F a.j of the Arnoldus i…

Origine ed evoluzione della equazione universale per il calcolo della perdita di suolo

Analisi di frequenza delle piene

Misure dell’erodibilità del suolo a scala di parcella nell’area sperimentale di Sparacia

Effetto della lunghezza della parcella sulla perdita di suolo

Linee guida per l'applicazione della Universal Soil Loss Equation (USLE) in ambiente mediterraneo

Isoerosivity and erosion risk map for Sicily

This paper reviews simplified methods for evaluating the rainfall erosivity index and proposes two relationships for estimating the annual value of Wischmeier's rainfall erosivity index at sites equipped with recording and non-recording raingauges. For the Sicilian region, the FAO index was also found to represent the erosion risk. A regional relationship to estimate the standard deviation of the annual erosivity index is proposed. The isoerosivity map is plotted by using 41 values of the rainfall erosivity index calculated by Wischmeier's procedure and 128 values estimated according to a relationship proposed by the authors. Finally, for each of 169 sites, an erosion risk index is calculat…

Roughness effect on the correction factor of surface velocity for rill flows

Flow velocity is one of the most important hydrodynamic variables for both channelized (rill and gullies) and interrill erosive phenomena. The dye tracer technique to measure surface flow velocity Vs is based on the measurement of the travel time of a tracer needed to cover a known distance. The measured Vs must be corrected to obtain the mean flow velocity V using a factor αv = V/Vs which is generally empirically deduced. The Vs measurement can be influenced by the method applied to time the travel of the dye-tracer and αv can vary in different flow conditions. Experiments were performed by a fixed bed small flume simulating a rill channel for two roughness conditions (sieved soil, gravel)…

Monitoraggio dell'erosione rill nell'area sperimentale di Sparacia

Incomplete self-similarity and flow velocity in gravel bed channels

Velocity measurements, previously carried out using both a miniature current flowmeter and an acoustic Doppler velocimeter, are used to verify the applicability of the incomplete self-similarity theory to deduce the velocity profile in a gravel bed channel. Then, for the velocity profiles having the maximum value below the free surface and for the S-shaped profiles, the power velocity distribution is corrected using a new divergence function. For each value of the depth sediment ratio the nondimensional friction factor parameter is calculated by integration of the measured velocity distributions in the different verticals of the cross section. Finally, a semilogarithmic flow resistance equa…

Connectivity in hydrology and sediment dynamics

Connectivity has emerged as a significant conceptual framework for understanding the transfer of surface water and sediment through landscapes. The concept has been widely adopted in the field of catchment hydrology but has also been valuable to investigate rates of soil erosion by water and sediment export across landscapes. To study connectivity, we gathered a group of scientists that worked on synthesizing and consolidating all theories and aspects of connectivity research. Within the EU-funded ESSEM COST Action CONNECTEUR (ES1306), five working groups were established: (a) theory, (b) measuring, (c) modelling, (d) indices, and (e) society. One of the outputs of this COST Action is this …

Supporting USLE-MM reliability by analyzing soil loss measurement errors

Sampling the collected suspension in a storage tank is a common procedure to obtain soil loss data. A calibration curve of the tank has to be used to obtain actual concentration values from those measured by sampling. However, literature suggests that using a tank calibration curve was not a common procedure in the past. For the clay soil of the Sparacia (Italy) experimental station, this investigation aimed to establish a link between the relative performances of the USLE-M and USLE-MM models, usable to predict plot soil loss at the event temporal scale, and soil loss measurement errors. Using all available soil loss data, lower soil loss prediction errors were obtained with the USLE-MM (e…

Il fattore di pratica antierosiva della USLE

New theoretical solution of the outflow process with a weir with complex shape

AbstractIn this paper, the outflow process of a weir with an irregular shape is studied using dimensional analysis and the incomplete self-similarity theory. The new unique stage–discharge relationship, which is deduced theoretically, represents a novel and comprehensive equation to describe the weir outflow process for a full range of flow and different geometric variables of weirs, including finite-crested weirs, broad-crested weirs with positive or negative crest slope, broad-crested weirs with an upstream, downstream, or both upstream and downstream crest ramps, and, triangular weirs with an upstream or downstream ramp. Finally the proposed stage–discharge relationship is calibrated usi…

Rilievi di perdita di suolo e di deflusso superficiale in parcelle sperimentali in presenza di una barriera di vetiver

Risposta erosiva di un bacino percorso da incendio in ambiente mediterraneo

Modeling Rainfall Erosivity by Measured Drop-Size Distributions

AbstractThe study of the detachment of soil particles due to rainfall erosivity requires knowledge of the energetic characteristics of the precipitation. In this paper, following a review of both the drop-size distribution (DSD) proposed by one researcher and the corresponding relationship for evaluating the kinetic power of rainfall, the reliability of that researcher’s DSD using the size distributions of raindrops detected by an optical disdrometer installed at Palermo (Sicily) is experimentally tested. Finally, an experimental verification of both the relationship proposed by two separate research teams for evaluating the specific and unit rainfall kinetic energy is carried out.

Verifiche sperimentali della USLE a scala di parcella in Sicilia

Processo di efflusso da uno stramazzo a profilo W

Testing a theoretical resistance law for overland flow on a stony hillslope

Overland flow, sediments, and nutrients transported in runoff are important processes involved in soil erosion and water pollution. Modelling transport of sediments and chemicals requires accurate estimates of hydraulic resistance, which is one of the key variables characterizing runoff water depth and velocity. In this paper, a new theoretical power–velocity profile, originally deduced neglecting the impact effect of rainfall, was initially modified for taking into account the effect of rainfall intensity. Then a theoretical flow resistance law was obtained by integration of the new flow velocity distribution. This flow resistance law was tested using field measurements by Nearing for the …

Processi di trasporto di particelle solide e nutrienti in bacini forestali

Deducing a Drain Spacing Formula by Applying Dimensional Analysis and Self-Similarity Theory

For designing a steady state drainage system a drain flow formula coupled with the Dupuit-Forcheimer form of the differential equation of groundwater flow is used. At first, in this paper the most applied drain flow formulas in steady-state conditions are reviewed and compared using as dependent variable the ratio between the maximum water table height and the distance between two lines of parallel drains. These equation are also tested using experimental field data measured in three plot drained by surface pipe drains having different value of drain spacing. Then, applying the dimensional analysis and the self-similarity theory, a new drain spacing formula is theoretically deduced and comp…

Assessing soil erosion in a small Sicilian basin by caesium-137 measurements and a simplified mass balance model

Abstract The caesium-137 technique affords both an alternative to conventional measurement methods and an effective quantitative estimate of soil redistribution at the basin scale. Among the available calibration relationships which link the degree of increase or depletion of the 137Cs activity relative to the baseline 137Cs input and sediment yield, the mass balance approach has received increased application for its physical basis. First, the applicability of the refined simplified point-based mass balance (RSPMB) model of Zhang et al. (1999) at the scale of the morphological unit is proposed herein. The 137Cs spatial distribution measured in a small Sicilian basin and the spatial distrib…

Experimental study on triangular central baffle flume

Abstract In this paper the results of the experiments performed to study the flow through a Triangular Central Baffle Flume (TCBF) are reported. The investigated flume consists of a triangular baffle of the apex angle of 75° with a given base width. The theoretical stage-discharge formula was deduced by applying the Buckingham's Theorem and incomplete self-similarity hypothesis and was calibrated using the laboratory measurements carried out in this investigation. The proposed stage-discharge formula is characterized by a mean absolute relative error of 7.4% and 72% of the data points are in an error range of ±5%. The results indicate that TCBF flume is characterized by a flow capacity high…

Analisi delle distribuzioni dimensionali delle gocce di pioggia rilevate mediante un disdrometro ottico

Il fattore climatico dell’equazione universale per il calcolo della perdita di suolo

Testing the Modified Sediment Delivery Model (MOSEDD) at SPA2 Experimental Basin, Sicily (Italy)

A new version of a spatially distributed sediment delivery model taking into account the hillslope sediment transport efficiency, named MOSEDD, is presented. This model gives estimates of basin sediment yield at event scale, which are more reliable than those obtained by the original SEDD. For SPA2 basin discretized into morphological units, four different calculation schemes of MOSEDD, including the original SEDD version, were applied. All parameterization schemes of the model were calibrated using 15 events measured at the outlet of the experimental basin in the period February 2005–February 2010. The model calibration was used to determine a relationship between the coefficient βₑ of the…

Response to ‘comment on “predicting event soil loss from bare plots at two Italian sites”’

In this paper, a response to the comment by Dr. Kinnell on “Predicting event soil loss from bare plots at two Italian sites”’ (Bagarello et al., Catena 109, 96–102, 2013) is provided.

Un criterio per la determinazione della tolleranza della perdita di suolo

Caratterizzazione delle precipitazioni ai fini erosivi - Analisi dei dati di letteratura

Mean flow, secondary currents and bed shear stress at a 180-degree laboratory bend with and without enhanced permeable groins as an Eco-friendly river structure

River restoration aims to apply environmentally-friendly structures for bank protection in meandering rivers to restore their natural habitat. Enhanced Permeable Groin (EPG) is a novel river restoration technique that can improve the fish habitat environment in a river system by creating a series of eco-friendly scour pools. This study reports the results of two groups of 3D velocity measurements in a 180-degree channel bend in cases with and without an EPG for clear water conditions to characterize the mechanisms leading to the primary stages of the scouring phenomenon. The analysis revealed that the presence of an EPG amplified the velocity magnitude in the regions near the tip of the van…

Nuovi e antichi paradigmi nello studio dei processi erosivi

A Maximizing Hydraulic Radius (MHR) method for defining cross-section limits in rills and ephemeral gullies

Abstract In this paper, a new method for determining the cross-section limits in rills and ephemeral gullies is proposed. This method is based on the estimate of the actual depth ha of each cross-section, which is the particular depth distinguishing the channel from the hillslope areas. The analysis showed that the actual depth corresponds to a particular bank slope sta occurring for the maximum value of the hydraulic radius R. The method was applied using a volumetric approach for calculating the hydraulic radius as the ratio between the volume of the whole investigated channel and its boundary lateral surface. The value of the bank slope st was derived by the DEM of the whole channel late…

Analysis of rill step–pool morphology and its comparison with stream case

In this paper, the morphology of step–pool features is analysed using rill measurements and literature data for streams. Close-range photogrammetry was used to carry out ground measurements on rills with step–pool units, shaped on a plot having slope equal to 14, 15, 22, 24 and 26%. Data were used to compare the relationships between H/L, in which H is the step height and L is the step length, and the mean gradient of the step–pool sequence, Sm, for streams or the slope of the step–pool unit, S, for rills. The relationship of H/L against Sm is widely used to test the occurrence of the maximum flow resistance condition in streams, which is associated with the range 1 ≤ (H/L)/Sm ≤ 2. Further …

Valutazione della produzione di sedimenti in un bacino forestato

Validating the use of caesium-137 measurements to estimate soil erosion rates in a small drainage basin in Calabria, Southern Italy

Recent concern for problems of soil degradation and the offsite impacts of accelerated erosion has highlighted the need for improved methods of estimating rates and patterns of soil erosion by water. The use of environmental radionuclides, particularly caesium-137 (137Cs), as a means of estimating rates of soil erosion and deposition is attracting increasing attention and the approach has now been recognised as possessing several important advantages. However, one important uncertainty associated with the use of 137Cs measurements to estimate soil erosion rates is the need to employ a calibration relationship to convert the measured 137Cs inventory to an estimate of the erosion rate. Existi…

Testing the shape-similarity hypothesis between particle-size distribution and water retention for Sicilian soils

Application of the Arya and Paris (AP) model to estimate the soil water retention curve requires a detailed description of the particlesize distribution (PSD) but limited experimental PSD data are generally determined by the conventional sieve-hydrometer (SH) method. Detailed PSDs can be obtained by fitting a continuous model to SH data or performing measurements by the laser diffraction (LD) method. The AP model was applied to 40 Sicilian soils for which the PSD was measured by both the SH and LD methods. The scale factor was set equal to 1.38 (procedure AP1) or estimated by a logistical model with parameters gathered from literature (procedure AP2). For both SH and LD data, procedure AP2 …

Testing GIS-morphometric analysis of some Sicilian badlands

Abstract Calanchi badlands are erosion landforms characterized by areas with scarce or absent vegetation, steep slopes, knife-edge divides and high erosion rates. They are originated by a combination of morphogenetic processes, partly similar to those shaping bigger fluvial landforms, and therefore can be considered as field “laboratories.” This paper presents the results of an investigation carried out in two badland sites located in Sicily, where the geometry of 25 calanchi has been characterized using Digital Elevation Models having a mesh size equal to 2 m. For each landform, a power length–volume relationship is established. This relationship demonstrates that length of calanchi channe…

New stage-discharge relationships for radial gates

Calibration of gates under free and submerged flow regimes is a classical hydraulic problem. In this paper dimensional analysis was applied to investigate both free and submerged flow conditions through a radial gate. The original Ferro’s method for submerged flow regime was modified by introducing the maximum allowable tail water depth permitting free flow. Based on Buckingham theorem and applying the Incomplete Self Similarity (ISS) concept different forms of the dimensional equations were proposed. According to the current available experimental data the most accurate dimensionless formula was proposed. The proposed dimensional equation not only is more accurate than the original Ferro’s…

Contributo al dimensionamento di una briglia con savanella a profilo W

Il risalto idraulico tipo B-jump:determinazione delle altezze coniugate

Interventi di riqualificazione fluviale del tratto terminale del torrente Petrolo

Stage–Discharge Relationship for an Upstream Inclined Grid with Transversal Bars

AbstractCheck dams with grids upgrading upstream are often used in mountain rivers, where intense sediment transport and steep slopes occur. In some cases, sloping grids are used in the construction of debris flow breakers. In this paper, the outflow process of an upstream-inclined grid with transversal bars is studied by using the dimensional analysis and the incomplete self-similarity theory. Next, the theoretical analysis shows that a power equation can be used for establishing the stage-discharge equation. The coefficient of the power equation depends on both the slope angle and the void ratio, whereas the exponent depends only on the slope angle. Finally, this deduced stage–discharge r…

A new expression of the slope length factor to apply USLE-MM at Sparacia experimental area (Southern Italy)

Abstract Predicting soil loss due to water erosion by empirical models is useful to assess the severity of the phenomenon in an area of interest and to predict the effect of alternative soil erosion control practices. The USLE scheme cannot be used at the Sparacia experimental area (Sicily, South Italy) to predict event soil loss per unit plot area, Ae, because experimental data suggest that, generally, Ae does not increase with plot length, λ. The USLE-MM scheme uses the runoff coefficient, QR, as an additional independent variable in order to develop an empirical model allowing prediction of storm soil loss values that do not necessarily increase with λ. According to this model, Ae is exp…

Testing the long term applicability of USLE-M equation at a olive orchard microcatchment in Spain

Abstract Universal Soil Loss Equation USLE-based erosion models have been used extensively to complement erosion measurements, to understand the interactions of the different geophysical features into erosion processes and to assess adequate alternative management practices and scenarios analyses. Despite its proved usefulness on different land-uses around the world, there is an urgent need to set up simple tools which do not require an advanced management expertise in terms of both choose of model parameters and calculation ability and which are accurate particularly at the event scale. In this paper the suitability of the Modified USLE (USLE-M) model at the event and the annual scale were…

Sull'impiego delle micorizze arbuscolari per la definizione della qualità dei suoli nei processi di desertificazione

Closure to "Analyzing turbulence intensity in gravel bed channel"

Sul profilo degli alvei torrentizi a monte di opere trasversali

Sperimentazione di campo sull'impiego delle soglie in legname e pietrame in ambiente mediterraneo

On the variation of the correction factor of surface velocity with the measurement vertical for shallow flows over rough beds

Considering that water flow energy affects the detachment of soil particles, the transport and deposit of the detached particles, the flow velocity is a key variable governing the soil erosion processes at the hillslope scale. The simple dye-tracer technique for measuring mean flow velocity can be applied in non-controlled field applications for which some measurement difficulties (e.g. due to sediment transport, and shallow flows) can occur. The correction factor is usually obtained as the ratio between the mean velocity, deriving from measurements of flow discharge and water depth, and surface velocity. Alternatively, the possibility of using the velocity profile in a given vertical to de…

Contributo al dimensionamento delle briglie a fessura lineare

Fenomeni di erosione localizzata a valle di opere trasversali: integrazione tra indagini di campo e di laboratorio

Testing the outflow theory of Malcherek by slit weir data

Abstract In this paper the flow-process of a slit weir is analyzed by the outflow theory of Malcherek. Average flow velocity over the slit weir is expressed in terms of head over weir and the momentum correction coefficient. The theoretically deduced stage-discharge formula was then calibrated using experimental data obtained for a ratio between the weir and the channel width ranging from 0.05 to 0.25. The deduced stage–discharge relationship allows to measure discharge values characterized by errors which are, for 91% of the measured values, less than or equal to ± 5%.

Sulla valutazione del deflusso minimo vitale dei corsi d'acqua siciliani

La ricerca nel settore dell'ingegneria naturalistica

Rill flow resistance law under sediment transport

Abstract Purpose In this paper, a deduced flow resistance equation for open-channel flow was tested using measurements carried out in mobile bed rills with sediment-laden flows and fixed bed rills. The main aims were to (i) assess the effect of sediment transport on rill flow resistance, and (ii) test the slope-flow velocity relationship in fixed bed rills. Methods The following analysis was developed: (i) a relationship between the Γ function of the velocity profile, the rill slope and the Froude number was calibrated using measurements carried out on fixed bed rills; (ii) the component of Darcy-Weisbach friction factor due to sediment transport was deduced using the corresponding measurem…

Testing slope effect on flow resistance equation for mobile bed rills

In this paper, a recently theoretically deduced rill flow resistance equation, based on a power-velocity profile, is tested experimentally on plots of varying slopes in which mobile bed rills are incised. Initially, measurements of flow velocity, water depth, cross-sectional area, wetted perimeter and bed slope conducted in 106 reaches of rills incised on an experimental plot having a slope of 14% were used to calibrate the flow resistance equation. Then, the relationship between the velocity profile parameter Γ, the channel slope, and the flow Froude number, which was calibrated using the 106 rill reach data, was tested using measurements carried out in plots having slopes of 22% and 9%. …

Predicting the equilibrium bed slope in natural streams using a stochastic model for incipient sediment motion

Monitoraggio degli eventi erosivi e calibrazione del modello SEDD nel bacino sperimentale SPA1 in Sicilia

Comment on "Measuring the flow resistance of submerged grass"

In this short note, the experimental data of Wilson and Horritt (2002.Hydrological Processes16: 2589–2598), jointlywith the measurements by Kouwenet al. (1969.Journal of Irrigation and Drainage Division, ASCE95: 329–342)and by Raffaelliet al. (2002 InProceedings XXVIII Convegno di Idraulica e Costruzioni Idrauliche, Cosenza, Italy;223–230), arefirstly used to test Kouwen’s approach. All experimental data are then used to calibrate aflow resistanceequation that was theoretically deduced by dimensional analysis and self-similarity theory

Analisi delle distribuzioni dimensionali delle gocce di pioggia acquisite mediante un disdrometro ottico

Una nuova formulazione per il calcolo della pendenza di sistemazione degli alvei montani

Elementi di Idraulica

Discussion of “Free Overfall in Inverted Semicircular Channels” by Subhasih Dey

Flow resistance law under equilibrium bed-load transport conditions

Abstract The uniform flow resistance equation, in the form due to Manning or Darcy-Weisbach, is often applied to determine the stage-discharge relationship of a river cross-section. The application of this equation, namely the slope-area method, allows to indirectly measure by water level readings the corresponding river discharge. In this paper, a recently deduced flow resistance equation for open channel flow was tested during conditions of equilibrium bed-load transport. First the flow resistance equation was determined by dimensional analysis and applying the condition of incomplete self-similarity for the flow velocity profile. Then the analysis was developed by the following steps: (i…

Testing the use of an image-based technique to measure gully erosion at Sparacia experimental area

The first part of this investigation was aimed at testing the use of a three-dimensional (3D) Digital Terrain Model (DTM) and a quasi-tridimensional (2.5D) Digital Elevation Model (DEM) obtained by a large series of oblique images of eroded channels taken from consumer un-calibrated and non-metric cameras. For two closed earth channels having a different sinuosity the ground measurement of some cross-sections by a profilometer (P) was carried out. The real volume of each channel was also measured by waterproofing it by a plastic film and filling it with a known volume of water. The comparison among the three methods (3D, 2.5D and P) pointed out that a limited underestimation of the total vo…

Testing a new sampler for measuring plot soil loss

Discussion of "preliminary Study of Surface Hydraulic Jumps" by S. Ahmed, Y. Ye, H. Liu, and N. Rajaratnam

In this paper the results of Preliminary Study of Surface Hydraulic Jumps” by S. Ahmed, Y. Ye, H. Liu, and N. Rajaratnam are discussed

Sul processo di efflusso da una griglia acclive con barre longitudinali

MISURA DELL’ERODIBILITA’ DEL SUOLO NELLE PARCELLE SPERIMENTALI DI SPARACIA, IN SICILIA

Nell’indagine è stata effettuata una determinazione sperimentale del fattore di erodibilità del suolo, K, della USLE basata sulle misure effettuate nel suolo argilloso di Sparacia. Il valore medio annuo del suddetto fattore, misurato su parcelle di lunghezza, , comprese tra 11 e 44 m, è risultato decrescente con . La stima indiretta del fattore di erodibilità è risultata del 46% inferiore rispetto alla misura effettuata nella parcella di riferimento, lunga cioè 22 m, e si è attestata su un valore intermedio tra le misure di K ottenute nelle parcelle di 33 e 44 m. Un simile effetto di scala è stato riconosciuto anche con riferimento ai valori annui e a quelli stagionali del fattore di erod…

Verifica sperimentale del fattore L della USLE-MM nell’area di Sparacia

Gully erosion in a small experimental catchment in SW Spain

Attività di ricerca, monitoraggio e modellazione dei processi erosivi nell'area pilota di Sparacia

GIS-MORPHOMETRIC ANALYSIS OF BADLANDS IN SICILY (ITALY)

Sicily is affected by severe erosion processes, locally causing large volumes of soil loss and high denudation rates. The effects of intense water erosion phenomena are testified by the occurrence of badlands that constitute a common landscape particularly in the central and southern areas of the Island, where slopes are frequently underlain by clay-rich deposits. This paper presents the first results of an investigation carried out in a badlands site located in the head sector of the Imera Meridionale river basin, where geometry of several erosion channels has been characterized. Since length of linear erosion landforms such as rills, ephemeral gullies and permanent gullies, has been prove…

Closure to "Assessing stage-discharge relationships for circular overflow structure" by M. Bijankhan and V. ferro

The paper is a closure to a previous article.

Saggio introduttivo alla ristampa anastatica di "Il salto di Bidone" di Duilio Citrini

Testing assumptions and procedures to empirically predict bare plot soil loss in a Mediterranean environment

Empirical prediction of soil erosion has both scientific and practical importance. This investigation tested USLE and USLE-based procedures to predict bare plot soil loss at the Sparacia area, in Sicily. Event soil loss per unit area, Ae, did not vary appreciably with plot length, l, because the decrease in runoff with l was offset by an increase in sediment concentration. Slope steepness, s, had a positive effective on Ae and this result was associated with a runoff coefficient that did not vary appreciably with s and a sediment concentration generally increasing with s. Plot steepness did not have a statistically detectable effect on the calculations of the soil erodibility factor of both…

Impiego dei funghi micorrizici arbuscolari come indicatori della qualità dei suoli

Effetto della copertura vegetale sui processi di erosione superficiale in alcune parcelle sperimentali calabresi

Experimental investigation of the outflow process over a triangular labyrinth weir

Analisi sperimentale del risalto idraulico su fondo orizzontale scabro

A full‐scale study of Darcy‐Weisbach friction factor for channels vegetated by riparian species

In this article, an open channel flow resistance equation, deduced applying dimensional analysis and incomplete self-similarity condition for the flow velocity distribution, was tested using measurements carried out in a full-scale channel equipped with three types of riparian plants (Salix alba L., Salix caprea L. and Alnus glutinosa L.). In the experimental channel, having banks lined with boulders, the vegetation branches were anchored in a concrete bottom. For each species, the measurements were carried out with plants having different amounts of leaves, different plant density and plant area index. The relationship between the scale factor Γ of the velocity profile and the Froude numbe…

Testing the stage-discharge relationship of a sharp crested sluice gate deduced by the momentum equation for a free-flow condition

Abstract In this paper the stage-discharge relationship of a sharp crested sluice gate is deduced by applying the momentum equation for a free flow condition. The theoretically deduced stage-discharge formula was then calibrated using experimental flume data obtained in previous investigations carried out for a free-flow condition. The deduced stage–discharge relationship is characterized by a momentum coefficient which is empirically estimated by the ratio between the height of the orifice and the water depth in the section upstream the gate. The relative errors are always less than or equal to - 10% to +10% and 71.4% of the errors are less than or equal to ± 2%.

I fattori topografici della USLE e la carta dell’erosione massima

Standardizing the use of fast-field cycling NMR relaxometry for measuring hydrological connectivity inside the soil

Hydrological connectivity inside the soil (HCS) is applied to study the effects of heterogeneities in complex environmental systems. It refers to both the spatial patterns inside the soil (i.e., structural connectivity [SC]) and the physical–chemical processes at a molecular level (i.e., functional connectivity [FC]). NMR relaxometry has been already applied to assess both SC and FC components of the HCS by defining SC and FC indexes. Here, fast-field cycling NMR relaxometry has been applied on a water suspended soil and a sediment to optimize the conditions to standardize the technique. Proton Larmor frequencies (ωL) from 0.01 to 25 MHz were used on samples suspended in three different rat…

Establishing a soil loss threshold for limiting rilling

In this paper a frequency analysis of event soil loss measurements collected in the period 1999–2012 at the microplots and plots of the Sparacia Experimental Area in Sicily, southern Italy, was developed. The analysis was carried out using the annual maximum soil loss measurements normalized by the mean soil loss measured at a given temporal and spatial scale. The empirical frequency distribution of the normalized variable was well fitted by two Gumbel’s theoretical probability distributions discriminated by a value of the normalized variable equal to 2. This last value discriminates between the relatively low and frequent values of the normalized variable and the high and rare ones. The an…

Regional analysis of soil erodibility in Sicily

Sull'applicabilità della legge di Hack nello studio dei processi idrologici

Alterazioni delle caratteristiche fisico-chimiche dei paletti di castagno in ambiente mediterraneo

Variable scale effects on hillslope soil erosion during rainfall-runoff processes

Abstract The variation of soil erosion across scales remains a controversial issue. A theoretical framework, coupling the normalized Green-Ampt equation for infiltration, 1D kinematic wave model for overland flow, and WEPP erosion modeling approaches for soil erosion, was used to explain and quantify the direct effect of scale on the soil erosion process. The results show that the relation between interrill erosion and slope length accords with a power-law decreasing trend, while the relation of rill erosion versus slope length shows a power-law increasing trend. Moreover, the power-law scaling of interrill erosion becomes more prominent with an increase of rainfall duration and intensity b…

Similitudine morfologica tra i rill e gli ephemeral gully rilevati in Sicilia

Processi erosivi e messa in sicurezza del territorio siciliano

Determinazione delle altezze coniugate del B-jump su fondo scabro

New technique for measuring water depth in rill channels

Abstract Water erosion is one of the most important soil degradation processes and rill erosion contribution to total soil loss is usually dominant as compared to interrill erosion. Rill erosion modelling requires that rill flow has to be adequately modelled. Flow depths in rills are typically of the order of millimeters to several centimeters and bed topography, characterized by steep slope values, significantly affects flow hydraulics. In this paper, a new technique for measuring the water depth inside a rill channel is proposed and the effects on flow resistance estimate are examined. This technique couples an accurate ground survey of the rill channel, obtained by close-range photogramm…

MEASURING FIELD RILL ERODIBILITY BY A SIMPLIFIED METHOD

Many process-oriented erosion prediction models reproduce rill erosion as affected by site-specific parameters, as for example, rill erodibility, and thus, their practical application requires the measurement of these parameters or their estimate. The aim of this paper was establishing a method for indirectly measuring field rill erodibility. A simple mathematical approach based on a known soil detachment equation and accounting for the rill erosion dynamic process is applied. Field measurements carried out for seven natural rainfall events occurring at the plots of the Sparacia experimental station, southern Italy, are used for indirectly measuring the rill erodibility of the investigated …

Discussion of “EDR in Circular Channels” by Subhasish Dey

New stage-discharge relationship for cylindrical and semi-cylindrical edged sluice gates

Abstract Gates are simple hydraulic structures which have been widely used for flow control and measurement in irrigation networks. In this paper new sluice gates with cylindrical and semi-cylindrical edges were introduced and the flow movement below these types of gates was experimentally investigated for both free- and submerged-flow conditions. The Buckingham theorem of dimensional analysis and the self-similarity theory were applied for developing the stage-discharge relationships for the two investigated flow conditions. For these cylindrical and semi-cylindrical edged gates and a free-flow condition, the proposed stage-discharge relationship was characterized by an estimate error less…

A NEW VERSION OF THE USLE-MM FOR PREDICTING BARE PLOT SOIL LOSS AT THE SPARACIA (SOUTH ITALY) EXPERIMENTAL SITE

Improving empirical prediction of plot soil erosion at the event temporal scale has both scientific and practical importance. In this investigation, 492 runoff and soil loss data from plots of different length,  (11 <  < 44 m), and steepness, s (14.9 < s < 26.0%), established at the Sparacia experimental station, in Sicily, south Italy, were used to derive a new version of USLE-MM model, by only assuming a value of one for the topographic length, L, and steepness, S, factors for  = 22 m and s = 9%, respectively. An erosivity index equal to (QREI30)b1, QR and EI30 being the runoff coefficient and the event rainfall erosivity index, respectively, with b1 > 1 was found to be …

VAlidazione del modello distribuito SEDD per la stima dell'erosione idrica in un bacino calabrese

Valutazione del fattore colturale per le coperture agrarie

Comment on ?Measuring the flow resistance of submerged grass? by C. A. M. E. Wilson and M. S. Horritt,Hydrological Processes 16: 2589-2598

In this short note, the experimental data of Wilson and Horritt (2002. Hydrological Processes16: 2589–2598), jointly with the measurements by Kouwen et al. (1969. Journal of Irrigation and Drainage Division, ASCE95: 329–342) and by Raffaelli et al. (2002 In Proceedings XXVIII Convegno di Idraulica e Costruzioni Idrauliche, Cosenza, Italy; 223–230), are firstly used to test Kouwen's approach. All experimental data are then used to calibrate a flow resistance equation that was theoretically deduced by dimensional analysis and self-similarity theory. Copyright © 2005 John Wiley & Sons, Ltd.

Measuring rill erosion at plot scale by a drone-based technology

The traditional direct method (i.e. metric ruler and rillmeter) of monitoring rill erosion at plot scale is time consuming and invasive because it modifies the surface of the rilled area. Measuring rill features using a drone-based technology is considered a non-invasive method allowing a fast field relief. In the experimental Sparacia area a survey by a quadricopter Microdrones md4-200 was carried out, and this relief allowed the generation of a Digital Elevation Model (DEM), with a mesh size of 1 cm and a resolution elevation equal to 2 mm, for three plots (L, G and C) affected by rill erosion. At first for the experimental L plot, which is 44 m long, the rill features were surveyed by a …

MANUAL SAMPLING AND TANK SIZE EFFECTS ON THE CALIBRATION CURVE OF PLOT SEDIMENT STORAGE TANKS

In many experimental soil erosion plots, runoff is collected and carried by a conveyance system to a sequence of storage tanks. If the soil loss is measured by collecting, after mixing, samples of the stored suspension, then a calibration curve between the actual mean concentration (C) and the measured concentration (Cm) in the storage tank occurs. The aim of this article was to evaluate experimentally the factors affecting the relationship between C and Cm. For a sandy loam soil, the replicated measurements of Cm (20 samples) for two values of the actual concentration (C = 5 and 25 g/L) showed that the variability of the measurements of Cm is low and confirmed the reliability of a calibrat…

Possibilità d'impiego di soglie in legname e pietrame in ambiente mediterraneo

Verifica applicativa di tre modelli di stima dell’erosione idrica mediante il concetto di modello fisico

Sul concetto di portata dominante in alcuni corsi d'acqua del territorio calabro-lucano

Esperienze sull'efflusso da uno sfioratore a profilo W

Closure to “Experimental Study of Central Baffle Flume” by F. Lotfi Kolavani, M. Bijankhan, C. Di Stefano, V. Ferro, and A. Mahdavi Mazdeh

This is a Closure of the discussions on the paper “Experimental Study of Central Baffle Flume” by F. Lotfi Kolavani, M. Bijankhan, C. Di Stefano, V. Ferro, and A. Mahdavi Mazdeh

Sequent Depth Ratio of a B-Jump

A B-jump is defined as the jump having the toe section located on a positively sloping upstream channel and the roller end on a downstream horizontal channel. This jump often occurs in the stilling basins with a horizontal bottom and located downstream of a steep channel. For a B-jump, a completely theoretical approach is not sufficient to solve the momentum equation and to establish the sequent depth ratio. In this paper, by using the laboratory measurements carried out in this investigation, some available empirical relationships useful for estimating the sequent depth ratio are tested. Then, by using the Π theorem of the dimensional analysis and the incomplete self-similarity theory, a g…

La qualità ambientale del sistema fluviale

VERIFICA DEL MODELLO CSI PER LA STIMA DELLA PERDITA DI SUOLO

La previsione dell’erosione idrica alla scala temporale del singolo evento riveste particolare interesse dal momento che la perdita di suolo complessiva di un periodo pluriennale è generalmente determinata dagli eventi più rilevanti. Recentemente, utilizzando le misure di perdita di suolo ottenute su parcelle nude installate in tre stazioni sperimentali italiane (Sparacia, in Sicilia; Masse, in Umbria; Caratozzolo, in Calabria), è stato sviluppato un modello empirico, denominato CSI (Central and Southern Italy), per la stima della perdita di suolo alla scala dell’evento. La presente memoria riporta i risultati della verifica di applicabilità del suddetto modello che è stata condotta utilizz…

Twenty years of scientific activity at Sparacia experimental area. Quaderni di Idronomia Montana 33

The main purpose of this booklet is to give to the participants to the Palermo’s Conference of the EU COST ACTION ES1306 - CONNECTING EUROPEAN CONNECTIVITY RESEARCH - CONNECTEUR a general idea of the scientific activity that was carried out in the past 20 years on the basis of the data collected at the Sparacia experimental station for soil erosion measurement, in Sicily, South Italy. The booklet includes a presentation of the experimental site, a description of the applied methods and procedures for measuring soil erosion processes at the Sparacia experimental area, and an illustration of the developed methodologies for predicting soil erosion from plots, small basins, rills and gullies. I…

Measuring rill erosion using structure from motion: A plot experiment

Abstract In this paper the results of a plot experiment on rill erosion are reported. The rill network, manually incised on the soil and further shaped by a clear inflow discharge, was surveyed using the three-dimensional photo-reconstruction (3D-PR) technique which allows to obtain a digital terrain model (DTM) by a large series of oblique images of the channel from consumer un-calibrated and non-metric cameras. The three-dimensional (3D) DTM and the quasi-tridimensional (2.5D) model were generated by Agisoft Photoscan software. For a single rill channel, the reliability of the 3D image-based ground measurements of morphological and hydraulic variables was positively tested by the correspo…

Contributo al dimensionamento di una briglia a fessura con profilo lineare doppio

L’obiettivo della sistemazione idraulica del tratto montano di un corso d’acqua e assicurare una condizione di stabilita per il cavo fluviale, mediante il raggiungimento di una condizione di equilibrio permanente tra la portata solida e quella liquida (Benini, 1984), facendo ricorso ad interventi di tipo strutturale capaci, nel rispetto della vigente normativa in tema di tutela  ambientale, di conservare e preservare gli ecosistemi preesistenti a valle (Ferro, 2006, 2008).

Discussion of “Discharge Characteristics of Weirs of Finite Crest Length with Upstream and Downstream Ramps” by Amir Hossein Azimi, Nallamuthu Rajaratnam, and David Z. Zhu

C. Di Stefano; V. Ferro; and M. Bijankhan, Aff.M.ASCE Researcher, Dipartimento di Scienze Agrarie e Forestali, Universita degli Studi di Palermo, Viale delle Scienze, Palermo 90128, Italy. E-mail: costanza.distefano@unipa.it Full Professor, Dipartimento di Scienze Agrarie e Forestali, Universita degli Studi di Palermo, Viale delle Scienze, Palermo 90128, Italy (corresponding author). E-mail: vito.ferro@unipa.it Ph.D. Candidate, Irrigation and Reclamation Engineering Dept., Univ. of Teheran Karaj, P.O. Box 31587-4111, Karaj 31587-77871, Iran. E-mail: bijankhan@ut.ac.ir

A pedotransfer function for estimating the soil erodibility factor in Sicily

The soil erodibility factor, K, of the Universal Soil Loss Equation (USLE) is a simple descriptor of the soil susceptibility to rill and interrill erosion. The original procedure for determining K needs a knowledge of soil particle size distribution (PSD), soil organic matter, OM, content, and soil structure and permeability characteristics. However, OM data are often missing and soil structure and permeability are not easily evaluated in regional analyses. The objective of this investigation was to develop a pedotransfer function (PTF) for estimating the K factor of the USLE in Sicily (south Italy) using only soil textural data. The nomograph soil erodibility factor and its associated firs…

Indagine sperimentale di pieno campo sulla formazione dei rill

Determinazione del profilo di velocità e di intensità della turbolenza in canali vegetati

In questa memoria i profili sperimentali della velocità longitudinale misurati in un canale rettilineo di laboratorio con vegetazione sommersa flessibile sul fondo, vengono utilizzati per testare l’applicabilità della legge tangente iperbolica, in genere utilizzata per interpretare il profilo di velocità nello strato di mescolamento (mixing layer). L’adattamento del profilo tangente iperbolica, sia a tutte le distribuzioni sperimentali di velocità presentate in questo lavoro che a quelle misurate da Ghisalberti & Nepf (2002) in differenti condizioni idrodinamiche, ha consentito di localizzare sempre il punto di flesso del profilo ad una distanza prossima all'altezza della vegetazione infles…

Distribuzioni di probabilità della perdita di suolo parcellare

Simple flume with a central baffle

Abstract In this paper the stage-discharge relationship of a flume with a central baffle is theoretically deduced using the Buckingham-Theorem of the dimensional analysis and the self-similarity theory. The new stage-discharge equation is calibrated by the measurements carried out by Peruginelli and Bonacci using a baffle having a given throat length and five different values of the contraction ratio. Finally, for a given throat length, a relationship linking the discharge with the upstream water depth, the contraction ratio and the contracted width is deduced.

Closure to “Stage–Discharge Relationship for an Upstream Inclined Grid with Transversal Bars” by C. Di Stefano and V. Ferro

Valutazione del fattore colturale per le coperture forestali

Monitoraggio dell'erosione rill a scala di parcella

Processi dissipativi su rampe in pietrame a differente granulometria

Experimental Modeling of Submerged Pivot Weir

An inclined rectangular overflow structure, also called a pivot weir, consists of a rectangular plate, angled downstream from the vertical, that can be used as an upstream water level control device. A pivot weir is submerged when the upstream water level is influenced by the downstream flow depth. In this paper, to investigate factors influencing submerged flow conditions, an extensive experimental program including 251 experimental trials was carried out using weir inclination angles of 39.6°, 53°, 85°, and 90° and weir heights ranging from 0.263 to 0.312 m. A formula to distinguish between free and submerged flow conditions was developed using the Π theorem of dimensional analysis and th…

Sul dimensionamento idraulico della briglia a fessura trapezia rovescia

Le briglie aperte, a differenza delle opere di tipo tradizionale, operano un arresto discriminato del materiale solido trasportato dalla corrente fluviale contribuendo al mantenimento dell’equilibrio dei tratti a valle della sistemazione ed alla alimentazione solida del litorale interessato dalla presenza della foce del corso d’acqua. Nella nota per il caso della briglia a fessura viene, inizialmente, descritto il funzionamento idraulico del manufatto. Per il caso di fessura trapezia rovescia vengono poi presentate le equazioni disponibili per la soluzione dei classici problemi della tecnica. Vengono fornite, infine, sia per il caso del problema di verifica che per quello di progetto delle …

Storia ed attualità dell'abaco di Shields

Contributo alla applicazione del metodo della corrivazione per i bacini siciliani

Predicting soil loss on moderate slopes using an empirical model for sediment concentration

Summary The objective of this investigation was to estimate event soil loss per unit area from bare plots in central and southern Italy using an empirical model for sediment concentration. The analysis was developed using data collected on bare plots differing in length (11–44 m) and slope (10–26%) at three Italian stations (Masse, Umbria; Caratozzolo, Calabria; Sparacia, Sicily). At first, an analysis was carried out, using the experimental data collected at Sparacia, to establish a relationship between sediment concentration and hydrological variables, such as runoff, rainfall amount and single storm erosion index. Then, an empirical model to estimate plot soil loss as a function of rainf…

Dissipative analogies of step-pool features: From rills to mountain streams

Abstract In this paper the dissipative similarity of step-pool units at different spatial scales ranging from rills to streams is analyzed. This investigation benefits from the latest theoretical advances in open channel flow resistance, high-resolution topography from close-range photogrammetry applied to rill erosion and the availability of published data from literature on step-pool streams. At first, the integration of a power velocity distribution allowed to obtain a theoretically-based expression of Darcy-Weisbach friction factor, in which Γ function and δ exponent of the velocity profile are included. Then this theoretically-deduced flow resistance relationship is calibrated and test…

Raindrop size distribution and terminal velocity for rainfall erosivity studies. A review

Abstract The knowledge of the rainfall drop size distribution (DSD) at the land surface is essential for understanding precipitation mechanisms affecting soil erosion processes. Rainfall erosivity is defined as the potential of rain to cause erosion and it can be evaluated by rainfall kinetic power, which is determined by DSD and raindrop terminal velocity. This paper firstly deals with the raindrop terminal velocity estimate. Then the most widely used DSD are reviewed highlighting the difference between the raindrop size distribution per unit volume of air and that per unit area and time. The reliability of the available kinetic power-rainfall intensity relationships and their application …

Resistenze al moto in alvei granulari in condizioni di macroscabrezza

Sediment delivery processes and the spatial distribution of caesium-137 in a small Sicilian basin

The sediment delivery processes occurring in a small Sicilian basin are modelled using the spatially distributed SEDD model recently proposed by Ferro and Minacapilli. The model is applied by using soil data (grain-size distribution, organic matter content, etc.) of 129 samples uniformly distributed over the study area and compiling the available information (topographic map, soil data, etc.) into a Geographical Information System. Finally, the predictive capability of the distributed sediment delivery approach is tested experimentally using the caesium-137 measurement technique. The comparison between calculated sediment yield and the corresponding measured caesium-137 loss is used to vali…

Atlante della qualità dei suoli del bacino del Fiume Imera Meridionale

Predicting maximum annual values of event soil loss by USLE-type models

Abstract Previous experimental investigations showed that a large proportion of total plot soil erosion over a long time period is generally due to relatively few, large storms. Consequently, erosion models able to accurately predict the highest plot soil loss values have practical importance since they could allow to improve the design of soil conservation practices in an area of interest. At present USLE-based models are attractive from a practical point of view, since the input data are generally easy to obtain. The USLE was developed with specific reference to the mean annual temporal scale but it was also applied at the event scale. Other models, such as the USLE-M and the USLE-MM, app…

Deducing the stage-discharge relationship of rectangular broad and sharp-crested contraction devices

Flumes with a local contraction of the channel width are a common way for accurately measuring the flow discharge. In this paper, the outflow process of rectangular broad and sharp-crested contraction devices is modeled using the dimensional analysis and the incomplete self-similarity condition. The proposed theoretical stage-discharge relationship is tested using measurements available in the literature. The proposed power equation is characterized by a value of the exponent close to 1.5 and a coefficient depending on the contraction ratio. The proposed flow-measuring flumes are characterized by a good accuracy of the measured discharge (ranging from -2.71 to 3.28% for the broad-crested co…

Flow velocity profile and turbulence characteristics in a vegetated straight flume

Vegetation affects the hydrodynamic conditions of an open channel flow with direct implications in physical and biophysical processes. In this paper, the vertical flow velocity distribution of a vegetated flow has been analyzed using experimental data collected in a straight flume. The experimental velocity distributions are positively compared with the hyperbolic tangent profile of a pure mixing layer previously verified by Ghisalberti and Nepf (2002). Peculiarly, for different flow and vegetative conditions, fitting of the hyperbolic tangent profile to the experimental velocity distributions has allowed the localization of the inflection point of the velocity profile at a distance from th…

Sulla determinazione della lunghezza del roller nel caso di risalto tipo B-jump

Misura dell'erosione rill mediante rilievo aereo a bassa quota

Dissipative scaling of step-pool features

Abstract This paper focuses on the dissipative similarity of step-pool units at rill, flume and stream scale. This investigation is carried out using recent advances in open channel flow resistance, applications of close-range photogrammetry to rill erosion, available published data on step-pool features in flumes and streams and a new dataset of measurements in fixed bed step-pool rills. A theoretically-based equation for calculating the Darcy-Weisbach friction factor obtained by integration of a power velocity profile is presented. The scale factor Γ of this power velocity profile, which is included in the flow resistance equation, was previously calibrated (Eq. 10) for mobile bed rills w…

Testing simple scaling in soil erosion processes at plot scale

Abstract Explaining scale effects for runoff and erosion improves our understanding and simulation ability of hydrological and erosion processes. In this paper, plot scale effects on event runoff per unit area (Qe), sediment concentration (Ce) and soil loss per unit area (SLe) were checked at El Teularet-Sierra de Enguera experimental site in Eastern Spain. The measurements were carried out for 31 events occurring in the years 2005 and 2007 in bare ploughed plots ranging from 1 to 48 m2. The analysis established the scaling relationship by dimensional analysis and self-similarity theory, and tested this relationship at different temporal scales ranging from event to annual scale. The dimens…

Simple flume for flow measurement in sloping open channel

First, this paper presents a new flume for measuring flow discharge in sloping channels, originally proposed by Samani and Magallanez for use in a horizontal channel. The flume is obtained by inserting two semicylinders in a rectangular cross section. Then, using dimensional analysis and the self-similarity theory, the stage-discharge relationship of the flume is theoretically deduced. For determining the two coefficients of the power stage-discharge equation, some experimental runs are carried out using flumes characterized by different values of the contraction ratio (ranging from 0.17 to 0.81) and of the flume slope (ranging from 0.5 to 3.5%). Finally, for a given range of the contractio…

Indagine di campo sul comportamento idraulico dei rill a scala di parcella

Assessing hydrological connectivity inside a soil by fast-field-cycling nuclear magnetic resonance relaxometry and its link to sediment delivery processes

Connectivity is a general concept used to represent the processes involving a transfer of matter among the elements of an environmental system. The expression “hydrological connectivity inside the soil” has been used here to indicate how spatial patterns inside the soil (i.e., the structural connectivity) interact with physical and chemical processes (i.e., the functional connectivity) in order to determine the subsurface flow (i.e., the water transfer), thereby explaining how sediment transport due to surface runoff (i.e., the soil particle transfer) can be affected. This paper explores the hydrological connectivity inside the soil (HCS) and its link to sediment delivery processes at the p…

La misura dei processi erosivi

Erosione localizzata a valle di soglie di fondo

Establishing soil loss tolerance: an overview

Soil loss tolerance is a criterion for establishing if a soil is potentially subjected to erosion risk, productivity loss and if a river presents downstream over-sedimentation or other off-site effects are present at basin scale. At first this paper reviews the concept of tolerable soil loss and summarises the available definitions and the knowledge on the recommended values and evaluating criteria. Then a threshold soil loss value, at the annual temporal scale, established for limiting riling was used for defining the classical soil loss tolerance. Finally, some research needs on tolerable soil loss are listed.

Applying the bootstrap technique for studying soil redistribution by caesium-137 measurements at basin scale

Abstract The use of the bootstrap technique to estimate the reference level of137 Cs in an uneroded site is tested. The analysis is developed using 137Cs measurements made in a small experimental Sicilian basin. In the reference area the 137Cs activity is normally distributed with a known sample mean value, m equal to 94.4 mBq cm−2. The influence of137 Cs reference site sampling was determined generating samples having a fixed size, N and six different values of the sample coefficient of variation, CV, by a Monte Carlo technique. Then, for each size N, the probability distribution of the mean μ of the sequences generated by Monte Carlo technique is defined. The soil redistribution is determ…

Variable power-law scaling of hillslope Hortonian rainfall–runoff processes

Hydrological studies focused on Hortonian rainfall–run-off scaling have found that the run-off depth generally declines with the plot length in power-law scaling. Both the power-law proportional coefficient and the scaling exponent show great variability for specific conditions, but why and how they vary remain unclear. In the present study, the scaling of hillslope Hortonian rainfall–run-off processes is investigated for different rainfall, soil infiltration, and hillslope surface characteristics using the physically based cell-based rainfall-infiltration-run-off model. The results show that both temporally intermittent and steady rainfalls can result in prominent power-law scaling at the …

Caratteristiche degli ephemeral gully in Sicilia

Monitoring and predicting sediment yield in a small Sicilian basin

Identifying areas of a basin that are most sensitive to erosion have stimulated the study of within–basin variability of the sediment–delivery processes and the use of spatially distributed models. To verify the reliability of a sediment–delivery distributed model applicable at the morphological unit scale (i.e., the area of clearly defined aspect, length, and steepness), experiments were carried out at mean annual and event scales in a small Sicilian basin. A Geographical Information System is briefly presented into which the measurements carried out at the basin outlet (runoff, sediment yield, etc.) and other point and areal information (soil erodibility, digital terrain model, etc.) were…

Statistical distribution of soil loss and sediment yield at Sparacia experimental area, Sicily

Abstract An analysis of the statistical distribution of event soil loss was carried out using the data collected in the period 1999–2008 at the microplots and plots of the Sparacia experimental area (Sicily, Italy). For a given microplot size, the analysis allowed to establish that the soil loss frequency distribution was skewed. Using the soil loss normalized by the event mean value, the analysis also showed that the frequency distributions corresponding to different microplot and plot sizes were overlapping, i.e. all distributions were extracted by the same statistical population. The developed analysis allowed to suggest that the soil loss of a given return period can be estimated using …

Measuring hydrological connectivity inside soils with different texture by fast field cycling nuclear magnetic resonance relaxometry

Abstract The locution “hydrological connectivity inside the soil” is generally used to disclose how the spatial patterns inside the soil affect the physical–chemical processes at a molecular level to influence water transfer into the soil, the surface runoff and related sediment transport. Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometry has been used to measure both structural and functional connectivity by two indexes indicated as structural (SCI) and functional (FCI) connectivity index. Here, FFC-NMR relaxometry has been applied to analyze three samples: two non-degraded soils, having different grain-size distribution, and a degraded soil sampled in a badland area. P…

Modelling sediment delivery processes by a stream tube approach

Abstract The sediment delivery processes due to the travel along a hydraulic path having an uniform slope and to the concave shape of the path are modelled. In particular, using a power equation for modelling the slope profile and RUSLE with two different expressions of the topographic factors, a criterion to define the erosion active slope length, i.e. the slope length in which no deposition processes occur, is initially proposed. Then, the RUSLE equation is adapted to concave profiles by a correction factor of the topographic factors depending on slope curvature. Finally, the deduced relationships (equations (19) and (27)) for correcting the topographic factors for a concave slope are exp…

Testing the USLE-M family of models at the Sparacia experimental site in south Italy

The modified Universal Soil Loss Equation (USLE-M) was empirically deduced by a statistical analysis of the original data set of soil loss measurements used to derive the Universal Soil Loss Equation (USLE). The USLE-M, including the effect of runoffin the event rainfall-runofferosivity factor, is characterized by a better capacity to predict event soil loss. At first, in this paper, using the soil erosion representative variables of USLE-M and the reference condition adopted in the USLE, the dimensional analysis and the self-similarity theory are applied to theoretically deduce a multiplicative equation similar to the USLE-M. Then using the database of the Sparacia experimental site, the a…

Modelli organizzativi e sviluppi legislativi della difesa del suolo nella regione siciliana

Experiments for testing soil texture effects on flow resistance in mobile bed rills

Abstract In this paper a recently theoretically deduced rill flow resistance equation, based on a power-velocity profile, was tested experimentally on plots of varying slopes and soil texture in which mobile bed rills are incised. Measurements of flow velocity, water depth, cross section area, wetted perimeter and bed slope conducted in rill reaches incised on experimental plots, having different slope values (9, 14, 22, 24 and 26%) and soil texture (clay fraction ranging from 42 to 73%), and literature data were used to calibrate the flow resistance equation. In particular, the relationship between the velocity profile parameter Γ, the channel slope, the flow Froude number and texture frac…

Determinazione dell’erodibilità dei suoli

Possibilità di impiego di soglie in legname e pietrame in ambiente mediterraneo

Deducing the stage-discharge relationship for contracted weirs by the outflow theory of Malcherek

The aim of this paper was the deduction of a new stage-discharge relationship for a contracted weir, having a crest length less than the channel width, by using the Malcherek’s outflow theory. The average outflow velocity over the rectangular contracted weir was expressed in terms of the head over weir, the momentum correction coefficient and the ratio between the crest length and the channel width. This theoretically deduced stage-discharge formula was calibrated by measurements carried out for values of the ratio between the crest length and the channel width ranging from 0.3125 to 0.9375. In particular, a relationship to estimate the momentum correction coefficient for contracted weirs w…

CALIBRAZIONE DI MODELLI USLE-DERIVATI MEDIANTE I MASSIMI ANNUALI DELLA PERDITA DI SUOLO PER EVENTO

Numerosi risultati sperimentali hanno evidenziato che la perdita di suolo pluriennale di una parcella è influenzata apprezzabilmente dall’erosione che si verifica in un numero complessivamente limitato di eventi particolarmente gravosi. Conseguentemente, un intervento di conservazione del suolo calibrato sull’erosione media annua può risultare poco efficace in occasione degli eventi meteorici più significativi dal punto di vista dell’erosione complessiva. La disponibilità di modelli di previsione dell’erosione idrica parcellare in grado di fornire stime accurate dei valori più elevati della perdita di suolo alla scansione del singolo evento erosivo riveste pertanto interesse pratico, potend…

Indici di erosività per la stima della perdita di suolo a scala di evento

Field investigation on rilling in the experimental Sparacia area, South Italy

In this paper the results of a field investigation on rilling carried out in the experimental Sparacia area are reported. The measurements were made on a plot 6 m wide and 22 m long subjected to natural rainfalls. For ten rainfalls the total soil loss (interrill and rill erosion) was collected in a storage system consisting of two tanks arranged in series at the base of the plot. Rill morphology (rill length and cross-sections) was measured for five rainfall events, while the rill profile was surveyed for three events. First the contribution of each component (rill and interrill erosion) to total soil loss was established. Then the analysis allowed establishment of a power relationship betw…

Morphometric characterization of a calanchi inventory in Sicily, Italy

Calanchi are a frequent type of badland landscape of Sicily (Italy), usually located in the middle of crops or forests. They are characterized by heavily dissected terrains with unvegetated slopes, knife ridge edges, V-shaped valleys and channels with a dendritic pattern, which incise and extend headwards. Calanchi exhibit, in smaller temporal and spatial scales, many of the geomorphic processes and landforms that may by observed in a fluvial landscape, hence, this type of badland may be considered as micro-watersheds where geomorphic dynamics can be related to their geometric features. The aim of this investigation was to evaluate the morphometric characteristics of calanchi landforms in S…

A new approach for deducing the stage-discharge relationship of a triangular broad-crested device

In this paper, the outflow process of a triangular broad-crested device is examined using the dimensional analysis and the incomplete self-similarity theory. A new theoretical stage-discharge relationship is proposed, and its applicability is verified using measurements available in literature. The proposed power equation is characterized by a coefficient depending on device apex angle and a constant value of the exponent.

Closure to “Sequent Depth Ratio of a B-Jump” by Francesco Giuseppe Carollo, Vito Ferro, and Vincenzo Pampalone

Criteri di zonizzazione climatica nello studio dei processi di desertificazione in Sicilia

Rill flow velocity and resistance law: A review

Rills caused by runoff concentration on erodible hillslopes generally have very irregular longitudinal profiles and cross-section shapes. Rill erosion directly depends on the hydraulics of flow within the rills which may differ greatly from that in larger and regular channels like streams or rivers. At first, in this paper, a review of the two different approaches to estimate rill flow velocity, based on flow regime and flow resistance laws, is presented. Recent advances in measurements of rill geometry by the three-dimensional photo-reconstruction (3D-PR) technique, which allows one to obtain a Digital Terrain Model (DTM) by low-altitude aerial and terrestrial photogrammetry, are also disc…

Effects of Biochar Addition on Rill Flow Resistance

The development of rills on a hillslope whose soil is amended by biochar remains a topic to be developed. A theoretical rill flow resistance equation, obtained by the integration of a power velocity distribution, was assessed using available measurements at plot scale with a biochar added soil. The biochar was incorporated and mixed with the arable soil using a biochar content BC of 6 and 12 kg m−2. The developed analysis demonstrated that an accurate estimate of the velocity profile parameter Гv can be obtained by the proposed power equation using an exponent e of the Reynolds number which decreases for increasing BC values. This result pointed out that the increase of biochar content dump…

Analisi sperimentale del risalto idraulico su fondo orizzontale scabro

Discussion on 'Estimating depth-averaged velocities in rough channels'

In this short communication the four estimate criteria of the depth-averaged local velocity proposed by Byrd et al. (Earth Surface Processes and Landforms, 2000, Vol. 25, pp. 167-173) are compared both with the three-point method of Bathurst and with the average velocity obtained by integrating the velocity profile (FPa2) suggested by Ferro and Pecoraro (Water Resources Research, 2000, vol. 36, pp. 2761-2770). The comparison was carried out using 84 velocity profiles measured by an acoustic Doppler velocimeter in a rectangular flume with a gravel bed. Copyright © 2002 John Wiley and Sons, Ltd.

Un criterio geomorfologico di progettazione delle briglie in massi

L'impiego dell'ingegneria naturalistica nella pratica professionale

Monitoring plot soil erosion and basin sediment yield at Sparacia experimental area

Flow Resistance in Step-Pool Rills

Rills evolve morphologically, and the adjustment of rill channel geometry to flow affects the relationships among velocity, discharge, and slope. The resistance to flow in step-pool rills is mainly due to form-induced mechanisms and, in comparison, grain resistance is of minor significance. Previous studies on rill flow resistance have been performed exclusively for grainresistance conditions and use a stream flow equation. In this study, a new flow resistance equation, deduced by applying dimensional analysis and self-similarity theory, was applied to rill flow in step-pool channels. First, the incomplete self-similarity hypothesis was used for establishing a power flow velocity profile wh…

Contributo alla applicazione della formula razionale in termini probabilistici per i piccoli bacini siciliani

Using empirical and theoretical approaches for predicting the slope of siltation upstream of check-dams in mediterranean environment

Cento anni di stima della pendenza di sistemazione

Predicting the equilibrium bed slope in natural streams using a stochastic model for incipient sediment motion

In this paper, a method to predict the equilibrium bed slope in natural streams based on the incipient motion criterion is proposed. The method is based on the criterion suggested by Gessler to simulate the grain size distribution of the armour coat using the concept of critical shear stress of a sediment mixture. In particular, a different expression of the probability for a single particle size to be part of the armour coat is firstly proposed; then, a simple two-steps criterion is suggested to estimate the safety factor required by the proposed approach. The method is applied in three different Italian regions (Calabria, Basilicata, and Tuscany) and required several field campaigns invol…

Tecniche di Ingegneria Naturalistica

Indagine sulla pendenza di sistemazione dei corsi d'acqua a monte di opere trasversali. Il caso del torrente Alli in provincia di Catanzaro

La stima del profilo di sistemazione in due corsi d'acqua calabresi a differente pendenza. Indagini di campagna

Nel lavoro vengono riportati i risultati di una campagna di misure condotte in 2 corsi d’acqua calabresi interessati da interventi di sistemazione con briglie. L’obiettivo dell’indagine è servito a verificare la validità dell’approccio, basato sul concetto di moto incipiente, che consente di ottenere il valore della pendenza longitudinale stabile mediante il ricorso alla simulazione fisica del processo di armouring statico. Le analisi, condotte in 72 tratti stabili (40 per il torrente Cerasia e 32 per il torrente Melodari), hanno riguardato: il rilievo della pendenza longitudinale a monte delle opere, la misura della sezione trasversale, la costruzione della curva granulometrica del materia…

19. Valutazione del Rischio di Desertificazione

assente - capitolo di libro

Spatial variability of the relationships of runoff and sediment yield with weather types throughout the Mediterranean basin

Este artículo contiene 16 páginas, 6 figuras, 2 tablas.

Recenti acquisizioni sul moto delle correnti negli alvei in ghiaia ed in presenza di vegetazione

Variabilità delle misure parcellari di perdita di suolo nell'area sperimentale di Sparacia

Closure to “Theoretical End‐Depth‐Discharge Relationship for Free Overfall” by Vito Ferro

Effect of plot size on measured soil loss for two Italian experimental sites

The objective of this investigation was to determine empirically the plot width and length effects on runoff volume, Ve, soil loss, Ae, and sediment concentration, Ce, by using data collected, at the temporal scale of the erosive event, on bare plots differing in width (2 to 8 m) and length (11 to 22 m) for two Italian stations (Masse, Umbria; Sparacia, Sicily). Mean results differed by a maximum factor of 1.6 for Ve, 1.8 for Ae and 1.2 for Ce when plots differing in width were compared and by a maximum factor of 1.4 for Ve, 1.2 for Ae and 1.3 for Ce when comparison between plot lengths was conducted. Differences between two plot widths or two plot lengths were not statistically significant…

Comment on “Overland runoff erosion dynamics on steep slopes with forages under field simulated rainfall and inflow by C. Li and C. Pan”

Managing sloping landscapes to control soil erosion processes due to rainfall and runoff is a relevant problem, especially when the vegetation is absent or sparse. The aim of this paper was to investigate the applicability of a theoretically resistance law for overland flow under simulated rainfall, based on a power-velocity profile, using field measurements carried out by Li and Pan for three plots with planted forage species (Astragalus adsurgens, Medicago sativa and Cosmos bipinnatus).The relationship between the velocity profile parameter Γ, the flow Froude number and the rain Reynolds number was calibrated using the data by Li and Pan. The obtained overland flow resistance law was also…

Valutazione della qualità del clima e del suolo nella identificazione delle aree sensibili alla desertificazione in Sicilia

Closure to "New stage-discharge relationship for weirs of finite crest length"

L'articolo riporta la risposta di chiusura alla discussione sull'articolo originale "New stage-discharge relationship for weirs of finite crest length"

Stima dell'erosione idrica parcellare in due siti sperimentali italiani

Comparison between grain-size analyses using laser diffraction and sedimentation methods

A comparison between laser diffraction method (LDM) and the sieve-hydrometer method (SHM) was carried out for 228 soil samples representing a different texture classification sampled in a Sicilian basin. The analysis demonstrated that the sand content measured by SHM can be assumed equal to that determined by LDM technique, while the clay fraction measured by LDM was lower than that measured by the SHM. A set of equations to transform LDM results to SHM results was proposed. The influence of the LDM measurements of clay on the estimated percentage of silt + very fine sand particles (particle diameter ranging from 0.002 mm to 0.1 mm), which is useful for estimating soil erodibility, was also…

Simulazione dei deflussi per il bacino sperimentale SPA1 di Sparacia

Closure to “Extraction of the Flow Rate Equation under Free and Submerged Flow Conditions in Pivot Weirs with Different Side Contractions” by N. Sheikh Rezazadeh Nikou, M. J. Monem, and K. Safavi

Distribuzioni di velocità e di intensità della turbolenza in canali a fondo granulare in condizioni di macroscabrezza

Un nuovo modello per la stima dell'erosione in aree calanchive

Dye-tracer technique for rill flows by velocity profile measurements

Abstract Water flow on hillslope soil surface supplies energy which is required to detach soil particles, to transport and deposit sediments, therefore flow velocity is a key variable related to hillslope hydrodinamics of soil erosion processes. Among the different methods available for measuring velocity of shallow interrill and rill flow, the trace technique is widely used. Trace technique is applied by adding a material (salt, magnetic material, water isotope, floating object) and then measuring the speed of the material to travel a known distance from the injection point. When flow velocity is measured using a dye-tracing method, the mean velocity is calculated by multiplying the measur…

Indagine regionale sul trasporto solido in sospensione dei corsi d'acqua siciliani

Evaluating the Effects of Sediment Transport on Pipe Flow Resistance

In this paper, the applicability of a theoretical flow resistance law to sediment-laden flow in pipes is tested. At first, the incomplete self-similarity (ISS) theory is applied to deduce the velocity profile and the corresponding flow resistance law. Then the available database of measurements carried out by clear water and sediment-laden flows with sediments having a quasi-uniform sediment size and three different values of the mean particle diameter Dm (0.88 mm, 0.41 mm and 0.30 mm) are used to calibrate the Γ parameter of the power-velocity profile. The fitting of the measured local velocity to the power distribution demonstrates that (i) for clear flow the exponent δ can be estimated b…

Predicting soil loss in central and south Italy with a single USLE-MM model

Purpose: The USLE-MM estimates event normalized plot soil loss, Ae,N, by an erosivity term given by the runoff coefficient, QR, times the single-storm erosion index, EI30, raised to an exponent b1> 1. This modeling scheme is based on an expected power relationship, with an exponent greater than one, between event sediment concentration, Ce, and the EI30/Pe(Pe= rainfall depth) term. In this investigation, carried out at the three experimental sites of Bagnara, Masse, and Sparacia, in Italy; the soundness of the USLE-MM scheme was tested. Materials and methods: A total of 1192 (Ae,N, QREI30) data pairs were used to parameterize the model both locally and considering all sites simultaneously. …

TESTING THE GRAIN-SIZE DISTRIBUTION DETERMINED BY LASER DIFFRACTOMETRY FOR SICILIAN SOILS

In this paper the soil grain-size distribution determined by Laser Diffraction method (LDM) is tested using the Sieve-Hydrometer method (SHM) applied for 747 soil samples representing a different texture classification, sampled in Sicily. 005_Di_Stefano(599)_39 28-12-2011 15:01 Pagina 45 The analysis showed that the sand content measured by SHM can be assumed equal to the one determined by LDM. An underestimation of the clay fraction measured by LDM was obtained with respect to the SHM and a set of equations useful to refer laser diffraction measurements to SHM was calibrated using the measurements carried out for 635 soil samples. Finally, the proposed equations were tested using independe…

Analysing longitudinal turbulence intensity in vegetated channels

Vegetation altering hydrodynamic conditions of an open channel flow controls the exchanges of sediment, nutrients and contaminants. In this paper the turbulence structure of open-channel flow over a flexible grass vegetation is investigated. Velocity measurements were carried out, in a rectangular flume, using a 2D-ADV (Acoustic Doppler Velocimeter) for different values of stem concentration, water discharge, and bed slope. The experimental results showed that: 1) the maximum value of the longitudinal turbulence intensity occurs at a water depth close to the bent vegetation height; 2) the turbulence intensity damps for increasing values of the stem concentration; 3) above the vegetation hei…

Measuring Rainfall Kinetic Power in Two Sicilian Experimental Areas by Drop-Size Distribution Data

The rainfall kinetic energy, which affects soil erosion processes, can be calculated by the drop-size distribution (DSD) and falling velocity. This study presents the outcomes derived by the DSDs recorded with the same optical disdrometer in two experimental areas, located in Sicily (southern Italy). Specifically, the DSDs were recorded from March 2017 to December 2019 at Sparacia and from June 2006 to April 2014 at Palermo. The aims of this paper are both to compare the DSDs for the two sites and to evaluate the applicability of Gamma theoretical distribution. Moreover, the relations of rainfall kinetic power vs. rainfall intensity are assessed. Differences in DSDs, especially for rainfall…

Comments on “Mean velocity and turbulent characteristics of flow over half-cycle cosine sharp-crested weirs” by Salehi S., Esmaili K., Azimi A.H.

Abstract In this paper the stage-discharge equation of a half-cycle cosine weir is theoretically deduced applying the Π-Theorem of dimensional analysis and the self-similarity theory. The coefficients of the new stage-discharge relationships are estimated using the results of the experimental runs by Salehi et al..

L’evento alluvionale dell’Ottobre 2009 nel Messinese

La carta dell'erosione massima per gli studi dei processi di desertificazione in Sicilia

Estimating flow resistance in steep slope rills

Recent research recognized that the slope of 18% can be used to distinguish between the ‘gentle slope’ case and that of ‘steep slope’ for the detected differences in hydraulic variables (flow depth, velocity, Reynolds number, Froude number) and those representatives of sediment transport (flow transport capacity, actual sediment load). In this paper, using previous measurements carried out in mobile bed rills and flume experiments characterized by steep slopes (i.e., slope greater than or equal to 18%), a theoretical rill flow resistance equation to estimate the Darcy-Weisbach friction factor is tested. The main aim is to deduce a relationship between the velocity profile parameter Γ, the c…

Sul dimensionamento idraulico della savanella delle briglie

La carta dell'erosione potenziale del territorio siciliano

A simplified approach to estimate water retention for Sicilian soils by the Arya-Paris model

Application of the Arya and Paris (AP) model to estimate the soil water retention curve requires a detailed description of the particle-size distribution (PSD) because the scale factor a, relating the pore length of an ideal soil to that of the natural one, depends on the particle size distribution parameters. For a dataset of 140 Sicilian soils that were grouped in five texture groups, the logistic and linear models were applied to evaluate a, and the water retention values predicted by the AP model were compared with the measured ones. Using the parameters proposed by Arya et al. (1999), the two models yielded similar unsystematic root mean error of estimate (RMSEu). Therefore, their pote…

Rilievo e modellazione dell’erosione rill nell’area sperimentale di Sparacia

Tecniche di Ingegneria naturalistica e Sistemazioni idraulico-forestali

Comparing two applicative criteria of the soil erosion physical model concept

The physical model represented by a replicated plot has been suggested to be the best possible, unbiased, real world model to predict plot soil erosion. The aim of this investigation was to compare the original applicative criterion of the physical model concept proposed by Nearing with that later suggested by Bagarello et al. The comparison was performed by using three empirical soil erosion models (the Universal Soil Loss Equation [USLE], a modified USLE [USLE-MM], and the Central and Southern Italy [CSI] model) and plot soil loss data collected at the experimental station of Sparacia, in Sicily (southern Italy). The investigation showed that (i) the new criterion was generally more restr…

Il risalto idraulico tipo B-jump:determinazione della lunghezza del roller

A comprehensive analysis of Universal Soil Loss Equation-based models at the Sparacia experimental area

Improving Universal Soil Loss Equation (USLE)‐based models has large interest because simple and reliable analytical tools are necessary in the perspective of a sustainable land management. At first, in this paper, a general definition of the event rainfall‐ runoff erosivity factor for the USLE‐based models, REFₑ = (QR)ᵇ¹(EI₃₀)ᵇ², in which QR is the event runoff coefficient, EI₃₀ is the single‐storm erosion index, and b₁ and b₂ are coefficients, was introduced. The rainfall‐runoff erosivity factors of the USLE (b₁ = 0 and b₂ = 1), USLE‐M (b₁ = b₂ = 1), USLE‐MB (b₁ ≠ 1 and b₂ = 1), USLE‐MR (b₁ = 1 and b₂ ≠ 1), USLE‐MM (b₁ = b₂ ≠ 1), and USLE‐M2 (b₁ ≠ b₂ ≠ 1) can be defined using REFₑ. Then t…

Assessing dye-tracer technique for rill flow velocity measurements

Abstract Rill erosion is considered one of the most important processes affecting soil because of the large amount of soil loss. The rill network acts as sediment source and is able to transport both rill flow-detached particles and those delivered from the interrill areas. Small flow depth in a rill and steep slope values of its bed affect significantly flow hydraulics. When rill flow velocity is measured using a dye-tracing method, the mean velocity is calculated by multiplying the measured surface velocity of the leading edge of the tracer plume by a correction factor. The main uncertainty of the dye-tracing technique stands in the relationship between mean and surface flow velocity. In …

IMPIEGO DEL RADIONUCLIDE 137CS PER LA STIMA DEI PROCESSI EROSIVI IN UN BACINO FORESTATO

Il radionuclide cesio-137 (137Cs) è uno dei traccianti più utilizzati per stimare la perdita di suolo per erosione idrica. L'applicazione di questa tecnica alla scala di bacino richiede anzitutto l'acquisizione delle misure del radionuclide in punti distribuiti sulla superficie e l'utilizzo di modelli di conversione idonei a trasformare i valori di 137Cs in quantità di erosione netta o di deposito. La presente memoria si pone l'obiettivo di verificare l'affidabilità del modello di conversione esponenziale per stimare i processi erosivi in terreni interessati da coperture forestali. L'applicazione è stata condotta in un bacino sperimentale della Sila Greca per il quale sono disponibili alcun…

Measurements of rill and gully erosion in Sicily

This article reports the results of a field investigation aimed to characterize the morphology of both rills monitored at Sparacia experimental area and two ephemeral gullies (EGs) located in the Tremamargi basin, Sicily, Italy. At first, the available literature data together with the measurements carried out in this investigation were used to show that the EG length is a key parameter for the estimation of the eroded volume. Then, the comparison among the pairs length and volume corresponding to measured rills, EGs and gullies showed that the exponent of the power relationship is independent of the channelized erosion type (rill, EG and gully), while a different scale factor has to be use…

Discussion on "Free overfall in inverted semicircular channels" by Subhasih Dey

This discussion focalizes on the applicability of the free overfall as a measuring device in open channel flows depending on the accuracy of the stage-discharge relationship

Closure to “Explicit Equations for Uniform Flow Depth” by Vito Ferro and Michele Sciacca

Explicit equations for uniform flow depth

Conventional approach in uniform open channel flow is to express the resistance coefficient in the Manning, Darcy-Weisbach or Chezy form. However, for practical cross-sections, including rectangular and trapezoidal ones, the governing equation is implicit in the uniform water depth. For these sections the water depth, corresponding to known values of the flow discharge, slope channel and resistance coefficient, is presently obtained by trial and error procedure. In this paper exact analytical solutions of uniform flow depth for rectangular and trapezoidal section have been obtained in the form of fast converging power series.

Valutazione dei processi erosivi e ipotesi di intervento per la conservazione del sito archeologico di monte Alburchia

Estimating the USLE soil erodibility factor in Sicily, South Italy

The Universal Soil Loss Equation (USLE) is used by professionals and technicians to predict soil loss by water erosion and to establish soil conservation measures. One of the key elements of the USLE is the K factor, which is a measure of the soil erodibility. Given the difficulty in collecting sufficient data to adequately measure K, early in the USLE's history the soil erodibility nomograph method was developed to allow estimation of K based on standard soil properties. Since the nomograph approach was developed based on a small number of soils in the United States, it is necessary for other contexts to check the nomograph's ability to predict the soil's true erodibility. Considering that…

Comparing theoretically supported rainfall-runoff erosivity factors at the Sparacia (South Italy) experimental site

Interpreting rainfall‐runoff erosivity by a process‐oriented scheme allows to conjugate the physical approach to soil loss estimate with the empirical one. Including the effect of runoff in the model permits to distinguish between detachment and transport in the soil erosion process. In this paper, at first, a general definition of the rainfall‐runoff erosivity factor REFe including the power of both event runoff coefficient QR and event rainfall erosivity index EI30 of the Universal Soil Loss Equation (USLE) is proposed. The REFe factor is applicable to all USLE‐based models (USLE, Modified USLE [USLE‐M] and Modified USLE‐M [USLE‐MM]) and it allows to distinguish between purely empirical m…

Flow resistance law under suspended sediment laden conditions

Abstract The uniform flow resistance equation, in the form due to Manning or Darcy-Weisbach, is widely applied to establish the stage-discharge relationship of a river cross-section. The application of this equation, namely the slope-area method, allows to indirectly measure the corresponding river discharge by measurements of bed slope, water level, cross-section area, wetted perimeter and an estimate of channel roughness. In this paper, a recently deduced flow resistance equation for open channel flow was tested during conditions of suspended sediment-laden flow. First, the flow resistance equation was determined by dimensional analysis and by applying the condition of incomplete self-sim…

Preface: Proceedings of the 14th IASWS international conference

Preface to the Proceedings of the 14th IASWS international conference

FIELD TESTING OF THE SMBF FLUME

At first, in this paper the stage-discharge relationship of a new flume, originally proposed by Samani and Magallanez, for measuring flow discharge in open channels is reviewed. The flume is obtained inserting two semicylinders in a rectangular cross-section. Then, the results of some experimental runs carried out using horizontal flumes characterized by different values of the contraction ratio (ranging from 0.17 to 0.81) are used for determining the two coefficients of the power stage-discharge equation. Finally, the stage-discharge equation is tested using flow measurements carried out, in the period December 2004 – March 2006 in the Sicilian experimental SPA1 and SPA2 basins. Field test…

Rilievo del''erosione ephemeral gully in un piccolo bacino siciliano

Verifica sperimentale della tecnica LD per la determinazione della distribuzione granulometrica

Simultaneous Flow over and under a Gate

This paper reports the results of an investigation carried out to establish the stage-discharge relationship for a flow simultaneously discharging over and under a sluice or a broad-crested gate. The stage-discharge relationship is deduced by a theoretical analysis, based on the application of the Π-theorem of the dimensional analysis and the incomplete self-similarity theory, coupled with an experimental investigation carried out by using a laboratory flume.

Are calanco landforms similar to river basins?

In the past badlands have been often considered as ideal field laboratories for studying landscape evolution because of their geometrical similarity to larger fluvial systems. For a given hydrological process, no scientific proof exists that badlands can be considered a model of river basin prototypes. In this paper the measurements carried out on 45 Sicilian calanchi, a type of badlands that appears as a small-scale hydrographic unit, are used to establish their morphological similarity with river systems whose data are available in the literature. At first the geomorphological similarity is studied by identifying the dimensionless groups, which can assume the same value or a scaled one in…

Morphological characterization of calanchi (badland) hillslope connectivity

Calanchi, a type of Italian badlands created by a combination of water erosion processes and local geomorphological and tectonic controls, is a striking example of long-term landscape evolution. In small temporal/spatial scales, the calanchi exhibit many of the geomorphic processes and landforms that may be observed in fluvial landscapes, hence they may be considered as micro-basins where geomorphic dynamics and landscape features can be related. The goal of this research is testing the use of simple morphometric variables for assessing sediment connectivity of calanchi landforms. In order to detect the morphological characteristics controlling the landscape connectivity of calanchi basins,…

Friction Factor for Gravel-Bed Channel with High Boulder Concentration

This paper reports the results of an experimental investigation on flow resistance law for a gravel-bed channel having bed arrangements characterized by different values of the number of boulders. The dependence is studied of a parameter, proposed for describing the gravel-bed surfaces, on the boulder concentration and on the ratio between the median diameter of the coarser particles and the median diameter of the bed layer. Flume measurements carried out for the hydraulic condition of \Itransition\N and \Ilarge-scale\N roughness (1.5 ≤ \ih/\id\d5\d0 ≤ 6.9) show that the intercept of the semilogarithmic flow resistance law depends on the ratio and on boulder concentration. For concentration…

Analisi morfometrica di due aree calanchive in Sicilia (Italia)

Applicabilità della legge di Hack nello studio di alcuni processi idrologici nei bacini siciliani

Plot-scale measurement of soil erosion at the experimental area of Sparacia (southern Italy)

Obtaining good quality soil loss data from plots requires knowledge of the factors that affect natural and measurement data variability and of the erosion processes that occur on plots of different sizes. Data variability was investigated in southern Italy by collecting runoff and soil loss from four universal soil-loss equation (USLE) plots of 176 m2, 20 ‘large’ microplots (0·16 m2) and 40 ‘small’ microplots (0·04 m2). For the four most erosive events (event erosivity index, Re ≥ 139 MJ mm ha−1 h−1), mean soil loss from the USLE plots was significantly correlated with Re. Variability of soil loss measurements from microplots was five to ten times greater than that of runoff measurements. D…

Comments on “Measurement of dimensionless Chezy coefficient in step-pool reach (Case study of Dizin River in Iran)” by Torabizadeh A., Tahershamsi A., Tabatabai M.R.M

This paper is a comment on a previous published paper.

Comment on “Rill erosion processes on steep colluvial deposit slope under heavy rainfall in flume experiments with artificial rain by F. Jiang et al.”

Abstract Since rill flows are characterized by small water depths and steeply sloping channels, the corresponding hydraulic conditions are very different to those which are typically found in channels of streams and rivers. Furthermore, limited information is currently available on the effect of rainfall on flow resistance. The objective of this comment was to investigate the applicability of a recently theoretically deduced rill flow resistance equation, based on a power-velocity profile, using measurements carried out by Jiang et al. for both different slope steepness conditions and rainfall intensity. The relationship between the velocity profile parameter Γ, the channel slope and the fl…

Testing the Modified Sediment Delivery Model (MOSEDD) at SPA2 Experimental Basin, Sicily (Italy)

A new version of a spatially distributed sediment delivery model taking into account the hillslope sediment transport efficiency, named MOSEDD, is presented. This model gives estimates of basin sediment yield at event scale, which are more reliable than those obtained by the original SEDD. For SPA2 basin discretized into morphological units, four different calculation schemes of MOSEDD, including the original SEDD version, were applied. All parameterization schemes of the model were calibrated using 15 events measured at the outlet of the experimental basin in the period February 2005–February 2010. The model calibration was used to determine a relationship between the coefficient βe of the…

Calibrazione di un torbidimetro ottico per la misura della perdita di suolo a scala di parcella

Sistemazione dei bacini montani e difesa del suolo

Closure to “Applying Hypothesis of Self-Similarity for Flow-Resistance Law in Calabrian Gravel-Bed Rivers” by Vito Ferro and Paolo Porto

Sediment delivery processes at basin scale

Abstract Since eroded sediments are produced from different sources distributed throughout a basin, sediment delivery processes at basin scale have to be modelled by a spatially distributed approach. In this paper a new theoretically based relationship is proposed for evaluating the sediment delivery ratio, SDRi, of each morphological unit, i, into which a basin is divided. Then, using the sediment balance equation written for the basin outlet, a relationship between the basin sediment delivery ratio, SDRW and the SDRi is deduced. This relationship is shown to be independent of the soil erosion model used. Finally, a morphological criterion for estimating a coefficient, β, is proposed.

Effects of Boulder Arrangement on Flow Resistance Due to Macro-Scale Bed Roughness

Flow resistance in gravel-bed channels is not only affected by the shape and size of the roughness elements, but also by their arrangement on the channel bed surface (position to flow streamlines, spacing between elements, and their protrusion from the channel bed). Many investigations proved that open channel flow resistance can be obtained by integrating the power velocity profile. For a macro-scale roughness condition, this study aims to investigate the effect of different boulder arrangements on flow resistance. First, for each arrangement, the equation relating Γ function of the power velocity profile, the Froude number, and the channel slope was calibrated using available measur…

Contributo al dimensionamento idraulico delle briglie a fessura iperbolica

Rampe in pietrame

Morphological Similarity of Channels: From Linear Erosional Features (Rill, Gully) to Alpine Rivers

Flow resistance in mobile bed rills shaped in soils with different texture

Rill erosion is considered one of the most important soil processes because of the large amount of soil loss due to the development of a rill network able to promote an efficient transport of both rill flow-detached particles and those delivered from the inter-rill areas. Rill flow experiments are useful to overcome the gap in rill hydraulics knowledge and to test the reliability of currently applied uniform open channel flow equations for mobile bed rills. In this paper the applicability of a theoretical flow resistance equation, based on a power-velocity profile, to rill channels shaped on soils having different textures was investigated. The measurements (437 runs) of water depth, cross-…

Assessing sediment connectivity in dendritic and parallel calanchi systems

Abstract Calanchi, a type of Italian badlands created by a combination of water erosion processes and environmental constraints controlling their development, is a striking example of long-term landscape evolution. Sediment connectivity can be defined as the degree to which a system facilitates the fluxes of sediments through itself. The goal of this research is testing the use of simple morphometric variables for assessing sediment connectivity of calanchi landforms distinguishing between dendritic and parallel systems. For detecting the morphological characteristics controlling the sediment connectivity of calanchi basins, literature data (146 calanchi basins) and measurements carried out…

Comment on “Determining soil erodibility for the USLE-MM rainfall erosion model by P.I.A. Kinnell”

Abstract The measurements units of the USLE-MM soil erodibility factor are dependent on the exponent of the erosivity term. This circumstance prevents to compare soil erodibility values of sites differing by the value of this exponent. To overcame this problem, Kinnell (2018) suggested to relate the soil erodibility factor of the USLE-MM with that of USLE-M by a linear relationship with the objective to obtain a soil erodibility factor independent of the power of the erosivity term. The USLE-MB, which is a recently proposed model, has also a soil erodibility factor having measurement units common to USLE modelling environment. Kinnell (2018) also showed that the relationship between the pow…

Flood frequency analysis for Sicily, Italy

Analisi delle distribuzioni dimensionali delle gocce di pioggia rilevate in Sicilia

Indagine di campo sull'efficacia del vetiver per la conservazione del suolo e dell'acqua

Comparing flow resistance law for fixed and mobile bed rills

Rills caused by run-off concentration on erodible hillslopes have very irregular profiles and cross-section shapes. Rill erosion directly depends on the hydraulics of flow in the rills, which may differ greatly from hydraulics of flow in larger and regular channels. In this paper, a recently theoretically deduced rill flow resistance equation, based on a power–velocity profile, was tested experimentally on plots of varying slopes (ranging from 9% to 26%) in which mobile and fixed bed rills were incised. Initially, measurements of flow velocity, water depth, cross-section area, wetted perimeter, and bed slope, carried out in 320 reaches of mobile bed rills and in 165 reaches of fixed rills, …

Testing the “physical model concept” by soil loss data measured in Sicily

The best possible model to predict the erosion from an area of land has been suggested to be a physical model of the area that has similar soil type, land use, size, shape, slope and erosive inputs. Therefore, a replicated plot has to be considered the best possible, unbiased, real world model. In this paper the physical model concept was tested by using soil loss data collected on plots of different length at the experimental station of Sparacia, in Sicily (South Italy). This investigation supported the conclusions that i) a coefficient of determination between measured and predicted soil loss values of 0.77 has to be considered as the best-case prediction scenario and ii) an uncalibrated …

Discussion of "Discharge characteristics of weirs of finite crest length with upstream and downstream ramps"

A Discussion of the paper "Discharge characteristics of weirs of finite crest length with upstream and downstream ramps" is presented

Closure to "New stage-discharge equation for the SMBF flume"

Closure alle discussions sull'articolo "New stage-discharge equation for the SMBF flume"

La valutazione della pendenza di sistemazione

Flow measurement using circular portable flume

Abstract The circular portable flume is a simple device to measure discharge in circular drainage networks. Since the unit can be easily installed and removed, it is helpful in water distribution measurement and management. First in this paper the available studies are reviewed for highlighting the effect of both the contraction ratio and the flume slope on the stage-discharge relationship. Then the Buckingham's Theorem of the dimensional analysis and the self-similarity theory are used to deduce the stage-discharge curve of the circular flume. The new theoretical stage-discharge equation is calibrated by the literature available experimental data and those obtained in this experimental inv…

Rilievi del profilo di velocità in un canale con vegetazione sommersa

Erosione da ephemeral gully in un piccolo bacino siciliano

Deducing the USLE mathematical structure by dimensional analysis and self-similarity theory

The Universal Soil Loss Equation (USLE) was originally deduced by a statistical analysis of a large data set of soil loss measurements. The multiplicative structure of the model has been criticised due to the considerable interdependence between the variables. Using the soil erosion representative variables and the reference condition adopted in the USLE, the aim of this paper was to apply dimensional analysis and self-similarity theory to deduce the functional relationship among the selected variables. The analysis yielded a multiplicative equation, similar to the USLE. Therefore, this study suggested that the USLE has a logical structure with respect to the variables used to simulate the …

Effetto di differenti sistemi colturali sulla perdita di suolo in parcelle sperimentali ubicate in Calabria

Sicily: climatic and hydrologic features

Scala di efflusso del misuratore a cilindri in canale rettangolare a fondo orizzontale

Disporre di un semplice strumento di misura della portata idrica è fondamentale nelle applicazioni di campo, soprattutto quando il sito di misura risulta essere non facilmente raggiungibile come, ad esempio, nelle stazioni di misura del trasporto solido e di erosione idrica. Il misuratore a cilindri, costituito da due semicilindri ad asse verticale che ostruiscono parzialmente il deflusso liquido, è uno strumento adatto a questo scopo. Nella memoria è presentata una relazione di derivazione teorica della scala delle portate del misuratore a cilindri. In particolare la relazione proposta ha origine dall’equazione di Bernoulli applicata tra la sezione a monte dello strumento, dove si misura i…

Testing Sediment Connectivity at the Experimental SPA2 Basin, Sicily (Italy)

The concept of sediment delivery can be used as a measure of sediment connectivity, and it can be linked to the structural connectivity (morphological unit, slope length, slope steepness, travel time) of a basin and to the hydrological connectivity (rainfall–runoff processes at morphological unit scale). In this paper, the sediment connectivity concept was tested at basin scale applying SEdiment Delivery Distributed model, which takes into account the hillslope sediment transport, and using sediment yield measurements carried out at SPA2 experimental basin (Sicily, Italy). For the SPA2 basin discretized into morphological units, the SEdiment Delivery Distributed model was first calibrated a…

Saggio introduttivo alla ristampa anastatica di "Sulla sistemazione dei torrenti" di Carlo Valentini

Quantifying interrill and ephemeral gully erosion in a small Sicilian basin

Impiego della tecnica del cesio-137 per la stima della produzione di sedimenti in un bacino sperimentale calabrese

Testing a theoretically-based overland flow resistance law by Emmett’s database

Abstract The main aim of this paper was to test a recently theoretically deduced flow resistance equation, based on a power-velocity profile, using a wide database of available measurements carried out in laboratory and field experimental runs with overland flow under simulated rainfall. In comparison with previous calibrations and validations of this theoretically deduced flow resistance equation, the used database by Emmett is characterized by a wide range of rainfall intensities (from 79.2 to 303.5 mm h−1 for laboratory runs and from 178.3 to 215.9 mm h−1 for field investigations) and bed slopes (from 0.33 to 17% for laboratory runs and from 2.9 to 33.2% for field investigations). For th…

Determinazione delle altezze coniugate del risalto libero su fondo liscio e scabro

Analisi del processo dissipativo sulle rampe in pietrame, Rivista di Ingegneria Agraria

Closure to “New Theoretical Solution of Stage-Discharge Relationship for Slit Weirs” by Vito Ferro and Ismail Aydin

In this paper, the flow-process of a slit weir was analyzed on the basis of a theorem of dimensional analysis and incomplete self-similarity theory. The theoretically deduced stage-discharge formula then was calibrated using experimental data obtained for a ratio between the weir and the channel width, ranging from 0.05 to 0.25. The deduced stage-discharge relationship allowed measuring discharge values characterized by errors that, for 98% of the measured values, were less than or equal to +/- 5%. The performance of the proposed theoretical stage-discharge formula also was improved by introducing the Reynolds number (for 98.5% of the measured values the error was less than or equal to +/- …

COMPARING PARTICLE SIZE DISTRIBUTION ANALYSIS BY SEDIMENTATION AND LASER DIFFRACTION METHOD

In this paper a brief review of the laser diffraction method is firstly carried out. Then, for 30 soil samples having a different texture classification sampled in Sicilian basin, a comparison between the two techniques is developed. The analysis demonstrated that the sand content measured by Sieve-Hydrometer method can be assumed equal to the one determinated by laser diffraction technique while an overestimation of the clay fraction measured by Sieve-Hydrometer method respect to laser diffraction technique was obtained. Finally a set of equations useful to refer LD measurements to SH method was proposed.

Modelling the effects of a bushfire on erosion in a Mediterranean basin

A bushfire occurred in the Asinaro River basin in July 1998. The basin area is 55 km2 and about 74% of the whole area was set on fire. The aim of this paper is to test the influence of fire on both soil erosion and the spatial distribution of the areas characterized by the greatest sediment yield values. The RUSLE model and a spatial disaggregation criterion for sediment delivery processes (SEDD model) were used to test the effects of the bushfire. The basin was divided into 854 morphological units for calculating the topographic factor. The RUSLE climatic factor R was calculated using daily rainfall data. The soil erodibility factor was determined by sampling at sites distributed over the …

Confronto tra modelli di previsione e rilievi sperimentali della pendenza di sistemazione in un corso d'acqua calabrese

VERIFICA DI IPOTESI E PROCEDURE NELLA STIMA EMPIRICA DELLA PERDITA DI SUOLO PARCELLARE IN UN AMBIENTE MEDITERRANEO

La stima dell’erosione idrica mediante approcci empirici ha interesse sia scientifico sia applicativo. Nella presente indagine è stata condotta una verifica di ipotesi e procedure adottate nella USLE e in modelli basati sullo schema USLE per la stima della perdita di suolo da parcelle di suolo nudo nell’area sperimentale di Sparacia, in Sicilia. La perdita di suolo per unità di superficie del singolo evento erosivo, Ae, non è significativamente dipendente dalla lunghezza parcellare, λ, in quanto all’aumentare di λ si riduce il deflusso ma cresce la concentrazione dei sedimenti. I valori di Ae sono crescenti con la pendenza parcellare, s, in quanto il coefficiente di deflusso non varia appre…

Experimental Investigation of the Outflow Process over a Triangular Labyrinth-Weir

In this paper, the outflow process from a sharp-crested triangular labyrinth weir is studied. Applying dimensional analysis and the Π theorem, five dimensionless groups, describing the outflow process, are deduced. The measurements, carried out by using sharp-crested weirs placed in a flume, allowed to establish a dimensionless stage-discharge relation. According to this equation, the flow magnification is affected by either the length magnification ratio or head to one cycle width ratio. The proposed equation, which also satisfies two theoretical boundary conditions, was finally tested by using experimental measurements of different reservoir hydraulic models.

A new approach for deducing the stage-discharge relationship of triangular in plan sharp-crested weirs

Abstract In this paper, the outflow process of a triangular in plan sharp-crested weir is studied using the dimensional analysis and the incomplete self-similarity theory. The new stage-discharge is theoretically deduced and its testing is carried out using measurements available in literature.

New Stage-Discharge Equation for the SMBF Flume

AbstractFlumes for indirect discharge measurements are widespread and are characterized by a particular shape of the cross section area with various degrees of convergence and subsequent divergence. The flume named Samani, Magallanez, Baiamonte, Ferro (SMBF) is a simple and inexpensive instrument and its channel contraction is obtained by applying two semicylinders to the walls of a rectangular cross section. At first, in this paper a new stage-discharge equation for the SMBF flume is theoretically deduced. Then, this equation is experimentally calibrated using the laboratory measurements from the literature for different values of the contraction ratio. Finally the field measurements carri…

Relationship of Weather Types on the Seasonal and Spatial Variability of Rainfall, Runoff, and Sediment Yield in the Western Mediterranean Basin

Producción Científica

Indagine sperimentale su un semplice misuratore di portata per correnti a pelo libero su fondo inclinato

Slope threshold for overland flow resistance on sandy soils

Recent research on rill flows recognised that an 18% slope can be used to distinguish between ‘gentle’ and ‘steep’ slope cases for the detected differences in hydraulic (flow depth and velocity) and sediment transport variables (flow transport capacity, actual sediment load). The effects of slope on flow velocity, friction factor and transport capacity and their interactions affect process-based erosion modelling. The main aim of this paper is to investigate, for the first time, how slope affects the overland flow resistance on sandy soils, which are characterised by loose particles readily available to be transported and deposited. Using literature measurements carried out in sandy soils f…

Closure to “New Theoretical Solution of the Stage-Discharge Relationship for Sharp-Crested and Broad Weirs” by V. Ferro

A Closure to the paper “A new theoretical solution of the stage-discharge relationship for sharp-crested and broad weirs” is presented

Predicting plot soil loss by empirical and process-oriented approaches. A review

Soil erosion directly affects the quality of the soil, its agricultural productivity and its biological diversity. Many mathematical models have been developed to estimate plot soil erosion at different temporal scales. At present, empirical soil loss equations and process-oriented models are considered as constituting a complementary suite of models to be chosen to meet the specific user need. In this paper, the Universal Soil Loss Equation and its revised versions are first reviewed. Selected methodologies developed to estimate the factors of the model with the aim to improve the soil loss estimate are described. Then the Water Erosion Prediction Project which represents a process-oriente…

Flood Frequency Analysis for Sicily, Italy

In this paper a regional flood frequency analysis based on the two-component extreme value TCEV distribution is developed using flood data recorded in Sicily. The hierarchical approach, characterized by three investigation levels for estimating the parameters of the theoretical distribution, is discussed first. The highest level of homogeneity hypothesis with regard to the skewness coefficient was verified by using a Monte Carlo technique and taking account of the separation effect proposed by Matalas et al. in 1975. This analysis also showed 1 the inability of the generalized extreme value model to reproduce the empirical cumulative distribution function CDF of the skewness coefficients, a…

Applying the USLE Family of Models at the Sparacia (South Italy) Experimental Site

Soil erosion is a key process to understand the land degradation, and modelling of soil erosion will help to understand the process and to foresee its impacts. The applicability of the Universal Soil Loss Equation (USLE) at event scale is affected by the fact that USLE rainfall erosivity factor does not take into account runoff explicitly. USLE-M and USLE-MM, including the effect of runoff in the event rainfall– runoff erosivity factor, are characterized by a better capacity to predict event soil loss. The specific objectives of this paper were (i) to determine the suitable parameterization of USLE, USLE-M and USLE-MM by using the dataseries of Sparacia experimental site and (ii) to evaluat…

Analisi della geometria idraulica dei rill mediante il data-base del WEPP

Lo sviluppo iniziale dei rill può essere spiegato facendo ricorso alle caratteristiche idrauliche della corrente, quali la velocità media, il numero di Froude e la tensione tangenziale al fondo della corrente. Gli studi già condotti sull’idraulica dei rill hanno permesso di modellizzare la geometria idraulica dei solchi mediante un set di tre equazioni, di forma potenziale, che legano la velocità media u, il tirante medio h e la larghezza del solco w alla portata. L’obiettivo del presente lavoro è stato quello di verificare l’applicabilità delle suddette relazioni potenziali e determinare i relativi coefficienti facendo ricorso alle misure condotte su 33 siti sperimentali che costituiscono …

Similarity between morphological characteristics of rills and ephemeral gullies in Sicily, Italy

This paper reports the results of a field investigation aimed to establish morphological similarity between rills and ephemeral gullies. Rill measurements were made on 14 plots having a surface area of 22–352 m2 located on a 14·9% slope and on a plot 6·0 m wide and 22·0 m long having a uniform 22·0% slope. The plots are located on the experimental station for soil erosion measurements, ‘Sparacia’, of the Agricultural Faculty of Palermo University, in Sicily, Italy. All plots are subjected to natural rainfall. The measurements were made immediately following five events between November 2004 and December 2005. The ephemeral gully measurements were made on a cultivated area of about 120 ha, l…

Recenti acquisizioni nel settore delle sistemazioni idraulico-Processi di trasporto di particelle solide e di nutrienti in bacini forestali

Indagine sulla pendenza di sistemazione di un corso d'acqua calabrese. Confronto tra modelli di previsione e misure di campo

Testing a theoretical resistance law for overland flow under simulated rainfall with different types of vegetation

Abstract In this paper a recently theoretically deduced flow resistance equation, based on a power-velocity profile, was tested using data collected for overland flow under simulated rainfall carried out in plots with vegetation. The available data were obtained exploring a wide range of rainfall intensities (from 60 to 181 mm h−1) and slopes (from 3.6 to 39.6%), and with four different types of vegetation. The database, including measurements of flow velocity, water depth, cross sectional flow area, wetted perimeter and bed slope, was divided in four datasets (one for each vegetation type), which allowed the calibration of the relationship between the velocity profile parameter Γ, the slop…

Sulla stima del fattore colturale della USLE-MM per coperture forestali ad eucalitto

Il fattore colturale C della Universal Soil Loss Equation (USLE) esprime l’efficacia antierosiva della copertura vegetale nei riguardi del suolo. Per il caso di terreni coltivati esso varia con la rotazione colturale, con le pratiche agronomiche, con il livello di produttività del suolo, con la durata delle varie fasi vegetative e con la distribuzione temporale delle precipitazioni. Nell’ambito di suoli caratterizzati da copertura forestale il fattore C risulta legato, oltre che alle precipitazioni, anche alla percentuale di suolo effettivamente coperto, alla presenza o meno di pascolo, alle pratiche selvicolturali (tagli), al verificarsi di danni a seguito di incendi o fitopatologie, all’e…

Length Slope Factors for applying the Revised Universal Soil Loss Equation at Basin Scale in Southern Italy

In this paper, for a basin divided into morphological units, a distributed model based on the Revised Universal Soil Loss Equation (RUSLE), with different expressions for the topographic factors, and on the sediment delivery ratio of each morphological unit is used. At first, the caesium-137 data available from a Sicilian basin are calibrated with two different models [the Proportional Method (PM), the Simplified Mass Balance (SMB) model] to provide net soil loss data for each morphological unit. Then, for a selected expression of the topographic factor, the slope length exponent is calculated for each morphological unit, equating the calculated sediment yield with the net soil loss. The an…

Establishing a threshold for rainfall‐induced landslides by a kinetic energy–duration relationship

Many investigators have attempted to define the threshold of landslide failure, that is, the level of the selected climatic variable above which a rainfall-induced landslide occurs. Intensity–duration (I–d) relationships are the most common type of empirical thresholds proposed in the literature for predicting landslide occurrence induced by rainfall. Recent studies propose the use of the kinetic power per unit volume of rainfall (J m−2 mm−1) to quantify the threshold of landslides induced by rainfall. In this paper, the relationship between rainfall duration and kinetic power corresponding to landslides triggered by rain was used to propose a new approach to define the threshold for predic…

Studio della funzionalità fluviale di due torrenti siciliani

Valutazione delle resistenze al moto di una corrente su un fondo granulare eterogeneo

Il fattore di erodibilità del suolo e la carta dell’erosione potenziale

Calibrating storage tanks for soil erosion measurement from plots

Many plots for soil loss measurements are equipped with a sequence of tanks for measuring runoff volume and sediment concentration. The stored water volume is easily determined by a water depth measurement while the sediment concentration is often measured by collecting samples of the mixed suspension. In this paper, using the Π-theorem of dimensional analysis, the functional relationship describing the mixing of the suspension in the tank is expressed in a dimensionless form. The recognized dimensionless groups allow the establishment, for given soil and water depth in the tank, of the relationship (calibration curve) between the actual and the measured concentration. The calibration curve…

Closure to "experimental Modeling of Submerged Pivot Weir" by M. Bijankhan and V. Ferro

This paper is a Closure to “Experimental Modeling of Submerged Pivot Weir”.

Linking sediment yield and caesium-137 spatial distribution at basin scale

Abstract Identifying areas of the landscape that are most sensitive or susceptible to erosion stimulated the study of within-basin variability of the sediment delivery processes and the use of spatially distributed models coupled with Geographic Information Systems. The progress of sediment delivery distributed modelling is also dependent on the availability of measurements able to establish the link between eroded soil leaving an area and the patterns of erosion and deposition occurring along the hydraulic path from the considered area to the nearest stream reach. In this paper, the tracer technique using the radionuclide137Cs and its employment in sediment yield studies at basin scale are…

Flow resistance of overland flow on a smooth bed under simulated rainfall

In this paper a recently theoretically deduced flow resistance equation, based on a power-velocity profile, was tested using laboratory measurements by Yoon and Wenzel for an overland flow on a smooth bed under rainfall. These measurements of the Darcy-Weisbach friction factor, corresponding to a wide range of the flow Reynolds number (191–5700), were carried out for an overland flow under a simulated rainfall characterized by different intensity values ranging from 13 to 381 mm h−1. At first, the available measured values of flow velocity, water depth, cross sectional area, wetted perimeter and bed slope were used to calibrate the relationship between the velocity profile parameter Γ, the …

Evaluating the Effectiveness of Forest Crop to Mitigate Erosion Using a Sediment Delivery Distributed Model

In this paper sediment yield data, measured from 1978 to 1997 in a small experimental Calabrian basin reafforested with Eucalyptus trees (Eucalyptus occidentalis Engl.), and RUSLE (Revised Universal Soil Loss Equation) coupled with a sediment delivery distributed model are used to evaluate the antierosive effects of this forest cover. At first, the soil loss measureinents carried out in two experimental plots, located in the basin, are used to evaluate the crop and management factor C of RUSLE far Eucalyptus coppice. The reliability of the selected C factor value is verified by comparing, at an event scale, the measured and the calculated sediment yield values at the basin outlet. Then, a M…

Erosione d'alveo in presenza di soglie di fondo disposte in sequenza

Interventi di riqualificazione fluviale del tratto finale del torrente Roccella alla confluenza con il Fiume Alcantara

Assessing theoretical flow velocity profile and resistance in gravel bed rivers by field measurements

Previous studies showed that integrating a power velocity profile, deduced applying dimensional analysis and the incomplete self-similarity condition, the flow resistance equation for open channel flow can be obtained. At first, in this paper the relationship between the Gamma function of the power velocity profile, the channel slope and the Froude number, which was already empirically introduced in a previous paper, is now theoretically deduced. Then this relationship is calibrated using the field measurements of flow velocity, water depth and bed slope carried out in 101 reaches of gravel bed rivers available by literature. The proposed relationship for estimating Gamma function and the t…

Verifica di campo del misuratore a cilindri in un canale rettangolare a fondo orizzontale

Il misuratore a cilindri è un semplice strumento per la determinazione della portata idrica defluente in un canale rettangolare. Lo strumento è costituito da due semicilindri ad asse verticale posti in aderenza alle pareti del canale in modo da determinare un’ostruzione parziale al deflusso. La presenza del restringimento determina un rigurgito a monte dove la misura del tirante consente, mediante un’apposita relazione, di determinare la portata idrica. Nella memoria è presentata una verifica di campo del funzionamento del misuratore a cilindri sito nell’area sperimentale di Sparacia in Sicilia. Il misuratore è inserito in una canaletta a pendenza nulla di 12 cm di larghezza ed è caratteriz…

DEDUZIONE DEL FATTORE L DELLA USLE-MM NELLE PARCELLE SPERIMENTALI DI SPARACIA, IN SICILIA

Nell’indagine è stato messo a punto un modello alternativo per la stima della perdita di suolo parcellare che riproduce anche la relazione tra Ae e  dedotta sperimentalmente. L’approccio utilizzato è quello della USLE-MM, che presuppone l’introduzione, nel set di variabili indipendenti, del coefficiente di deflusso parcellare. Nel modello proposto, il fattore topografico L stabilisce un legame crescente tra Ae e  ma la perdita di suolo dovuta a un fissato evento di pioggia può anche diminuire al crescere della lunghezza allorquando, come verificato sperimentalmente, all’incremento di  risulta associata una diminuzione del deflusso. La verifica del modello proposto con set di dati indipen…

ESTIMATING SOIL PARTICLE-SIZE DISTRIBUTION FOR SICILIAN SOILS

The soil particle-size distribution (PSD) is commonly used for soil classification and for estimating soil behavior. An accurate mathematical representation of the PSD is required to estimate soil hydraulic properties and to compare texture measurements from different classification systems. The objective of this study was to evaluate the ability of the Haverkamp and Parlange (HP) and Fredlund et al. (F) PSD models to fit 243 measured PSDs from a wide range of 38 005_Bagarello(547)_33 18-11-2009 11:55 Pagina 38 soil textures in Sicily and to test the effect of the number of measured particle diameters on the fitting of the theoretical PSD. For each soil textural class, the best fitting perf…

Similitudine nelle caratteristiche morfologiche dei rill e degli ephemeral gully

Closure to “New Stage-Discharge Equation for the SMBF Flume” by Francesco Giuseppe Carollo, Costanza Di Stefano, Vito Ferro, and Vincenzo Pampalone

Experimental study and numerical simulation of inclined rectangular weirs

Inclined rectangular weirs, also named pivot weirs, are used both to adjust the upstream water level and to increase the flow capacity compared with that of normal rectangular weirs. However, the experimental studies available in the literature present contradictory conclusions for the inclined weir discharge capacity. In this paper, new experimental runs and numerical simulations were performed to investigate the effect of the rectangular weir inclination angle on the stage-discharge formula. The experiments were carried out using inclination angles ranging from 30° to 90°. Buckingham's theorem of dimensional analysis was used to obtain an equation for the flow magnification ratio (the dis…

Experimental Study of Central Baffle Flume

In this paper, the hydraulics of a central baffle flume (CBF) were experimentally studied. Extensive experimental runs were carried out to highlight the effects of different geometrical parameters such as baffle length, contraction ratio, and the length of upstream and downstream guide walls. Two different approaches, i.e., the Π theorem of dimensional analysis coupled with the incomplete self-similarity theory and the energy balance equation, were applied to deduce the stage–discharge formula of a CBF characterized by different geometrical parameters. The stage–discharge relationship deduced by the dimensional analysis approach was more accurate than that obtained by the energy approach. F…

New Solution of Classical Hydraulic Jump

This technical note, applying dimensional analysis and incomplete self-similarity, proposes a new functional relationship for the sequent depth ratio for hydraulic jumps over both smooth and rough horizontal beds. For the smooth bed condition, experimental measurements in the literature were used to calibrate the new relationship. For the rough bed condition the data of a previous investigation were used with new measurements carried out in a rectangular horizontal flume having a gravel bed. Finally, a generalized solution of the sequent depth ratio is proposed.

Ability of soil bacterial composition as an indicator of levels of soil erosion in a badland

Calanchi (plural of calanco) are typical Italian badlands created by a combination of morphogenetic processes (rill and interrill erosion, gullying, piping, and mass movements) mainly originated by the effect of water. Calanchi are characterized by the sparse and patchy distribution of vegetation, and, in interplant areas, the soil surface is colonized by an association of organisms known as biological soil crust (BSC). A morphometric analysis of 45 basins in the studied calanchi area, based on a high-resolution digital elevation model, showed those basins are sediment removal systems characterized by rapid and relevant erosion processes. The goal of the current research is to evaluate the …

Modelling sediment delivery using connectivity components at the experimental SPA2 basin, Sicily (Italy)

Sediment delivery ratio can be used as a measure of sediment connectivity and it can be linked to the structural connectivity (morphological unit, slope length, slope steepness, travel time) of a basin and to the functional connectivity (rainfall-runoff processes at morphological unit scale). In this paper the sediment connectivity approach was applied at basin scale both using Sediment Delivery Distributed (SEDD) model, which takes into account the hillslope sediment transport, and sediment yield measurements carried out at SPA2 experimental basin (Sicily, Italy). The expression of the sediment delivery ratio SDRi of a morphological unit was modified for highlighting two components corresp…

ESPERIMENTO DI SIMULAZIONE DELLA FORMAZIONE DEI RILL A SCALA DI PARCELLA

Nella memoria sono riportati i risultati di un esperimento di simulazione della formazione del canale di un rill condotto in una parcella avente una dimensione 2x7 m2 ed una pendenza del 14% realizzata dal Dipartimento di Scienze Agrarie e Forestali dell’Università di Palermo. Una rete di solchi, costituita da due canali principali, è stata, dapprima incisa sul suolo manualmente e successivamente modellata utilizzando una corrente idrica limpida. Sui solchi modellati è stato effettuato, in corrispondenza di 11 sezioni trasversali della parcella, il rilievo delle caratteristiche geometriche e idrauliche utilizzando un profilometro. L’indagine ha inoltre previsto la realizzazione sia di un mo…

Monitoraggio e previsione dell'erosione idrica

Scour around a Permeable Groin Combined with a Triangular Vane in River Bends

River restoration refers to the environmental and ecological aspect of river engineering and aims to improve the natural habitat of a river system using eco-friendly methods. This paper introduces a new river restoration technique for bank protection and restoration of meander bends by combining a permeable groin with a triangular vane. Nine different combinations of permeable groins with triangular vane including three different effective lengths and three angles of vane were investigated in a 180 degrees mild laboratory flume bend in clear water conditions. Based on experimental tests, scour geometrical patterns were analyzed, classified, and compared with each other. This analysis showed…

Predicting unit plot soil loss in Sicily, south Italy

Predicting soil loss is necessary to establish soil conservation measures. Variability of soil and hydrological parameters complicates mathematical simulation of soil erosion processes. Methods for predicting unit plot soil loss in Sicily were developed by using 5 years of data from replicated plots. At first, the variability of the soil water content, runoff, and unit plot soil loss values collected at fixed dates or after an erosive event was investigated. The applicability of the Universal Soil Loss Equation (USLE) was then tested. Finally, a method to predict event soil loss was developed. Measurement variability decreased as the mean increased above a threshold value but it was low als…

Comparison of grain-size analysis by laser diffractometry with sedimentation method

Stima dell' erodibilità rill nella'area sperimentale di Sparacia

Alterazioni delle caratteristiche fisico-chimiche e meccaniche dei paletti di castagno in ambiente mediterraneo

Rainfall erosivity over the Calabrian region

Abstract Following the results of a study carried out for the neighbouring Sicilian region, this paper reports a study of the applicability of the annual value, Faj, of the Arnouldus index to represent the erosion risk in Calabrian region. Firstly, By using 214 values of the mean annual value of the erosivity index, FF, and a Kriging interpolation method, an isoerosivity map is plotted. Then, in order to predict the erosion risk for an event of any return period, the probability distribution of the Faj index is studied. An in situ statistical analysis, carried out by using candidate distributions with two parameters (Gauss, LN2, EV1 and Weibull distribution), showed that the EV1 and LN2 law…

Studio sperimentale del risalto idraulico su fondo liscio orizzontale e pendente

An assessment of the global impact of 21st century land use change on soil erosion

Human activity and related land use change are the primary cause of accelerated soil erosion, which has substantial implications for nutrient and carbon cycling, land productivity and in turn, worldwide socio-economic conditions. Here we present an unprecedentedly high resolution (250 × 250 m) global potential soil erosion model, using a combination of remote sensing, GIS modelling and census data. We challenge the previous annual soil erosion reference values as our estimate, of 35.9 Pg yr−1 of soil eroded in 2012, is at least two times lower. Moreover, we estimate the spatial and temporal effects of land use change between 2001 and 2012 and the potential offset of the global application o…

Assessing an overland flow resistance approach under equilibrium sediment transport conditions

Abstract In this study, for the first time, a theoretically deduced flow resistance equation was tested for an overland flow under equilibrium sediment transport conditions using available experimental data by Liu et al. for five Chinese soils. Initially the relationship among the velocity profile parameter Γ, the channel slope, the flow Reynolds number, the Froude number and the sediment concentration was calibrated using 90 measurements of the available database (Loessial, Cinnamon and Black soil) and tested by other 60 measurements (Red and Purple soil). The results proved that the Darcy–Weisbach friction factor can be accurately estimated by the proposed theoretical approach, with error…

Modeling Rill Erosion at the Sparacia Experimental Area

In this paper the contributions of rill and interrill components to total soil erosion monitored at event scale at the Sparacia experimental area, Southern Italy, were firstly compared and the dominance of the rill component was detected. Then, the reliability of two empirical relationships between the rill length and its eroded volume and among the morphological variables (length, width, depth and volume) describing the channelized process was tested using both direct measurements of rills, carried out for the October 3, 2011 event, and those of ephemeral gullies surveyed on February 2010 at Sparacia. The measurements of rills detected by the direct field relief were compared with those ob…

Investigating the Performance of Enhanced Permeable Groins in Series

The enhanced permeable groin is a novel eco-friendly and cost-effective technique for bank protection and restoration of meander bends. The behavior of bed deformations due to the distance between the structures has to be studied to design enhanced permeable groins in series properly. In this study, scour morphologies around enhanced permeable groins in series, characterized by four different distances and located in a 180&deg

Flow resistance due to shrubs and woody vegetation

In this paper, a theoretical open channel flow resistance equation was verified using flow depth and discharge measurements carried out by Freeman et al. in a large channel, 2.44 m wide, for ten different types of uniform-sized plants (shrubs and woody vegetation). The plants, which are broadleaf deciduous vegetation commonly found in floodplains and riparian zones, were placed in staggered rows inside the channel whose bed was constructed to accept plants with their root systems. For each species, the available measurements were carried out by Freeman et al. with plants having different values of plant density, height, and bending stiffness. The available literature database (87 measuremen…

Verifica delle equazioni disponibili per la stima della potenza cinetica delle precipitazioni naturali

Nella memoria sono riportati i risultati delle indagini condotte utilizzando le distribuzioni dimensionali delle gocce di pioggia (DSD) rilevate mediante un disdrometro ottico installato, nel periodo Giugno 2006 - Marzo 2014, presso il Dipartimento di Scienze Agrarie e Forestali dell’Università degli Studi di Palermo e nel periodo Luglio 2015-Gennaio 2016 presso la stazione sperimentale di El Teularet in Spagna. Dopo aver aggregato le DSD per classi di intensità differenti in ampiezza, è stata determinata la potenza cinetica associando a ciascun diametro della DSD aggregata la relativa velocità di caduta calcolata mediante una relazione reperita in letteratura. I valori di potenza cinetica …

Scale effects on plot runoff and soil erosion in a mediterranean environment

Explaining scale effects for runoff and erosion improves our understanding of hydrological and erosion processes. In this investigation, plot-scale effects on event runoff per unit area, Qe, sediment concentration, Ce, and soil loss per unit area, SLe, were checked at the Sparacia (Italy) site. Similar information on the scale effects was obtained with different dependent variables, i.e., individual values of Qe, Ce, and SLe for each plot or the mean of their replicated values, and scale indicators, i.e., plot length, l, or plot area, A. The most common result, occurring for 57 to 62% of the events depending on the considered variable, was the lack of any scale effect. When scale effects we…

Measuring Field Rill Erodibility by a Simplified Method

Many process-oriented erosion prediction models reproduce rill erosion as affected by site-specific parameters, as for example, rill erodibility, and thus, their practical application requires the measurement of these parameters or their estimate. The aim of this paper was establishing a method for indirectly measuring field rill erodibility. A simple mathematical approach based on a known soil detachment equation and accounting for the rill erosion dynamic process is applied. Field measurements carried out for seven natural rainfall events occurring at the plots of the Sparacia experimental station, southern Italy, are used for indirectly measuring the rill erodibility of the investigated …

New-stage discharge relationship for weirs of finite crest lenght

AbstractThe flow process of weirs of finite crest length is analyzed on the basis of the dimensional analysis and incomplete self-similarity theory. The crest length is incorporated in the functional stage-discharge relationship for weirs of finite crest length. The theoretically deduced stage-discharge formula was then calibrated using the experimental data compiled in this research. According to the current experimental data it is also concluded that the performance of the proposed stage-discharge formula is better than the previous dimensional stage-discharge formulae. Also, the proposed stage-discharge formula is applicable for all types of the weirs, i.e., long-crested, broad-crested, …

Rill flow resistance law under equilibrium bed‐load transport conditions

In this paper, a recently deduced flow resistance equation for open channel flow was tested under equilibrium bed-load transport conditions in a rill. First, the flow resistance equation was deduced applying dimensional analysis and the incomplete self-similarity condition for the flow velocity distribution. Then, the following steps were carried out for developing the analysis: (a) a relationship (Equation) between the Γ function of the velocity profile, the rill slope, and the Froude number was calibrated by the available measurements by Jiang et al.; (b) a relationship (Equation) between the Γ function, the rill slope, the Shields number, and the Froude number was calibrated by the same …

A Comprehensive Check of Usle-Based Soil Loss Prediction Models at the Sparacia (South Italy) Site

At first, in this paper a general definition of the event rainfall-runoff erosivity factor for the USLE-based models, REFe = (QR)b1(EI30)b2, in which QR is the event runoff coefficient, EI30 is the single-storm erosion index and b1 and b2 are coefficients, was introduced. The rainfall-runoff erosivity factors of the USLE (b1 = 0, b2 = 1), USLE-M (b1 = b2 = 1), USLE-MB (b1 ≠ 1, b2 = 1), USLE-MR (b1 = 1, b2 ≠ 1), USLE-MM (b1 = b2 ≠ 1) and USLE-M2 (b1 ≠ b2 ≠ 1) can be defined using REFe. Then, the different expressions of REFe were simultaneously tested against a dataset of normalized bare plot soil losses, AeN, collected at the Sparacia (south Italy) site. As expected, the poorest AeN predict…

Testing the Universal Soil Loss Equation-MB equation in plots in Central and South Italy

Planning soil conservation strategies requires predictive techniques at event scale because a large percentage of soil loss over a long-time period is due to relatively few large storms. Considering runoff is expected to improve soil loss predictions and allows relation of the process-oriented approach with the empirical one, furthermore, the effects of detachment and transport on soil erosion processes can be distinguished by a runoff component. In this paper, the empirical model USLE-MB (USLE-M based), including a rainfall-runoff erosivity factor in which the event rainfall erosivity index EI30 of the Universal Soil Loss Equation (USLE) multiplies the runoff coefficient QR raised to an ex…

Sulla previsione della pendenza di equilibrio in alcuni corsi d'acqua calabresi mediante un approccio di tipo probabilistico

New Flow-Resistance Law for Steep Mountain Streams Based on Velocity Profile

This paper deduces a new flow-resistance equation for open-channel flow applying dimensional analysis and self-similarity theory. The incomplete self-similarity hypothesis is used to establish the flow velocity distribution whose integration gives the theoretical expression of the Darcy-Weisbach friction factor. The theoretical resistance equation then is tested by the available field measurements of flow velocity, water depth, river width and bed slope carried out in 653 reaches of several Canadian mountain streams. A relationship between the G function of the velocity profile and the channel slope and the flow Froude number is also established. The analysis shows that the Darcy- Weisbach …

Using plot soil loss distribution for soil conservation design

Abstract Soil conservation design is generally based on the estimation of average annual soil loss but it should be developed taking into account storms of a given return period. However, use of frequency analysis in soil erosion studies is relatively limited. In this paper, an investigation on statistical distribution of soil loss measurements was firstly carried out using a relatively high number of simultaneously operating plots of different lengths, λ (11, 22, 33 and 44 m) at the experimental station of Sparacia (southern Italy). Using a simple normalization technique, the analysis showed that the probability distribution of the normalized soil loss is independent of both the scale leng…

Validating erosion rate estimates provided by caesium-137 measurements for two small forested catchments in Calabria, southern Italy

Increasing concern for problems of soil degradation and the off-site impacts of accelerated erosion has generated a need for improved methods of estimating rates and patterns of soil erosion by water. The use of environmental radionuclides, particularly 137 Cs, to estimate erosion rates has attracted increased attention and the approach has been shown to possess several important advantages. However, the use of 137 Cs measurements to estimate erosion rates introduces one important uncertainty, namely, the need to employ a conversion model or relationship to convert the measured reduction in the 137 Cs inventory to an estimate of the erosion rate. There have been few attempts to validate the…

Una nuova teoria per lo studio dei processi di efflusso dagli stramazzi

Il processo di efflusso da uno stramazzo, di notevole interesse per le applicazioni pratiche, viene studiato applicando l’analisi dimensionale e la teoria dell’autosimilitudine incompleta. La nuova scala teorica di efflusso dedotta per gli stramazzi, in parete sottile e grossa e di differente forma geometrica, viene verificata facendo ricorso sia alle misure disponibili in letteratura sia ad apposite sperimentazioni di laboratorio.

Sul dimensionamento delle rampe in pietrame

Studi applicativi per la realizzazione della carta dell'erosione potenziale del territorio siciliano e del relativo sistema informativo territoriale

La sistemazione dei bacini idrografici - seconda edizione

Closure to "Deducing a drain spacing formula by applying dimensional analysis and self-similarity theory" by Vito Ferro

This paper is a closure of the discussions to the paper "Deducing a drain spacing formula by applying dimensional analysis and self-similarity theory"

Verifica del concetto di modello fisico in due stazioni di misura dell’erosione parcellare

Contributo all'applicazione del metodo della corrivazione ai bacini siciliani

Physical and hydraulic characterization of a clay soil at the plot scale

Summary The soil physical and hydraulic properties have to be determined for interpreting and simulating many hydrological processes. An investigation was carried out to determine the physical and hydraulic characteristics of a clay soil at the plot scale. An intensive sampling of the surface soil layer of two plots of 4 × 11 m2 was carried out by measuring, for each plot, dry soil bulk density, ρb, and antecedent soil water content, θi, at 88 sampling points and field-saturated soil hydraulic conductivity, Kfs, at 176 sampling points. A wide range of Kfs values (0.7–5107 mm h−1) were measured by the Simplified Falling Head (SFH) technique. For each variable, the two plots yielded very simi…

A modified applicative criterion of the physical model concept for evaluating plot soil erosion predictions

Abstract In this paper, the physical model concept by Nearing (1998. Catena 32: 15–22) was assessed. Soil loss data collected on plots of different  widths (2–8 m), lengths (11–44 m) and steepnesses (14.9–26.0%), equipped in south and central Italy, were used. Differences in width between plots of given length and steepness determined a lower data correlation and more deviation of the fitted regression line from the identity one. A coefficient of determination between measured, M , and predicted, P , soil losses of 0.77 was representative of the best-case prediction scenario, according to Nearing (1998). The relative differences, Rdiff  = ( P − M ) / ( P + M ), decreased in absolute value a…

Portable central baffle flume

This paper investigated the hydraulic characteristics of the triangular central baffle (TCB) flume. Laboratory tests were carried out to determine the flume dimensions. The field applicability of the proposed portable device was examined by on-farm installation. According to the laboratory tests, when the contraction ratio, r, was less than 0.39, the flow capacity was not affected by the ratio between the flume’s floor height and the throat width. The laboratory analysis also showed that there was no significant effect of installing an entrance ramp on the stage-discharge relationship for r<0.39, while the entrance ramp increased the discharge capacity for r>0.39. The stage-discharge …

Monitoraggio della perdita di suolo parcellare nell'area sperimentale di Sparacia

Rilievo e modellazione della rill erosion nell'area di Sparacia

Nella presente indagine, l’applicabilità sia delle relazioni che caratterizzano morfologicamente i rill di Sparacia sia di quelle che ne caratterizzano la geometria idraulica viene testata utilizzando nuove misure condotte in occasione dell’evento del 3 Ottobre 2011. Le suddette misure sono state effettuate su una parcella in cui sono stati rilevati 19 rill e 231 sezioni trasversali. Il confronto delle nuove misure con la relazione lunghezza-volume e con quella dedotta teoricamente sulla base dell’analisi dimensionale, entrambe calibrate con i dati rilevati in precedenti eventi, ha confermato l’applicabilità delle suddette espressioni.

ADV measurements of velocity distributions in a gravel-bed flume

Velocity measurements carried out by an acoustic doppler velocimeter (ADV) in a rectangular laboratory flume having a gravel bed are presented. The velocity profiles are measured in six verticals of the channel cross-section having an increasing distance (from 4 to 38.5 cm) from the flume wall. The experimental runs are carried out for five different bed arrangements, characterized by different concentrations of coarser elements, and for the two conditions of small- and large-scale roughness. For both hydraulic conditions, the velocity measurements are first used to test the applicability of the Dean profile and of the logarithmic profile corrected by a divergence function proposed in this …

Assessing flow resistance in gravel bed channels by dimensional analysis and self-similarity

Abstract In this paper a new flow resistance equation for open channel flow, based on the integration of a power velocity profile, was tested for gravel bed channels. First this flow resistance equation, theoretically deduced by dimensional analysis and incomplete self-similarity condition, was reported. Then a relationship between the Γ function of the velocity profile, the channel slope and the Froude number was calibrated by the available laboratory measurements of flow velocity, water depth and bed slope carried out in 416 flume experimental runs with a gravel bed. Then the relationship for estimating Γ function and the theoretical resistance equation was tested by 83 independent flume …

SULLA APPLICABILITÀ DELLA USLE-MM PER LA STIMA DISTRIBUITA DELLA PRODUZIONE DI SEDIMENTI

Nella memoria è presentata una nuova versione del modello distribuito SEDD (SEdiment Delivery Distributed model) che accoppia la RUSLE o la USLE-MM con un criterio spazialmente distribuito per la stima dei processi di trasferimento delle particelle erose all’interno di un bacino idrografico. In particolare, viene proposta l’applicazione a scala di bacino di un fattore di erosività, che tiene conto anche del processo di deflusso a scala di versante, e di un fattore di erodibilità del suolo determinati utilizzando le misure parcellari condotte nell’area sperimentale di Sparacia in Sicilia. Il modello è stato calibrato utilizzando le misure dei deflussi liquidi e solidi effettuate nei bacini s…

Morphometric analysis of two calanchi areas in Sicily (Italy) by exploiting high resolution Digital Elevation Models

In the Mediterranean areas, specifically in Sicily (Italy), irregular rainfalls, strong seasonal changes, scarce vegetation cover and, frequently, outcropping of clayey deposits favor water erosion phenomena. Badland landscapes are the result of severe erosion processes, characterized by steep slopes, sparse vegetation, high drainage density, rapid erosion rates and a shallow or non existing regolith profile. In this investigation we focused on the calanchi badland type, consisting of heavily dissected terrain with steep, unvegetated slopes and channels that rapidly incise and extend headwards. This research was carried out in two calanchi sites located in Sicily. The geometry of 25 badland…

SW—Soil and Water

Abstract Recent research has directed attention to the properties of the eroded material because of its influence in deposition phenomena and in carrying capacity of pollutant materials. In this paper, the spatial distribution of the content of nitrogen, phosphorus and total organic carbon is firstly deduced using the measurements carried out in 129 soil samples well distributed over the Sicilian Sparacia Basin and a Kriging interpolation method. Then the load of each chemical was calculated at morphological unit and basin scale using the above-mentioned spatial distributions and sediment yield values calculated by a parametric approach such as the revised universal soil loss equation (RUSL…

Monitoraggio della perdita di suolo nell'area sperimentale di Sparacia

Utilizzo di modelli bimodali per la descrizione della curva di ritenzione idrica del suolo

L’approfondimento dell’influenza della struttura sulle caratteristiche di ritenzione idrica del suolo può contribuire alla risoluzione dei problemi legati all’eterogeneità del mezzo poroso ed anche alla quantificazione della qualità fisica del suolo. In particolare, nei suoli naturali strutturati, la presenza di un dominio dei pori strutturali (porosità inter-aggregati) e di un dominio dei pori matriciali (porosità intra-aggregati) può essere descritta mediante un’espressione della curva di ritenzione idrica di tipo bi-modale. L’indagine ha riguardato 40 suoli siciliani, per i quali è stato applicato alle misure sperimentali di ritenzione idrica il modello bimodale proposto da Dexter et al.…

A generalized stage-discharge relationship for sharp-crested power-law weirs by dimensional analysis and self-similarity

Weirs are characterized by a stage-discharge relationship which mainly depends on the shape and dimensions of the hydraulic structure. A weir with symmetrical power-law sides is a versatile weir that can produce some known weir types (rectangular, triangular, parabolic) as special cases. In this paper, the outflow process of sharp-crested power-law weirs is investigated using the dimensional analysis and the incomplete self-similarity theory. A new generalized theoretical stage-discharge relationship is proposed, and its applicability is tested using measurements available in the literature for different weir types.

Sequent depth ratio of B-jumps on smooth and rough beds

A hydraulic B-jump has the toe section located on a positively sloping upstream channel and the roller end on a downstream horizontal channel. This paper analyses the B-jump on a rough bed, such as at the transition from a block ramp to the stilling basin. Laboratory measurements of the sequent depth were carried out using three different channel slopes for the rough bed and a single slope for the smooth bed. A solution useful for estimating the sequent depth ratio in a rectangular channel for different relative roughness and bed slope is proposed and positively tested by the present measurements. This solution can also be used to estimate the sequent depth ratio of classical hydraulic jump…

Closure "Stage-discharge relationship for an upstteam inclined grid with transversal bars"

The paper is a closure of “Stage-Discharge Relationship for an Unpstream Inclined Grid with Transversal Bars”

Closure to “Experimental Study of the Stage-Discharge Relationship for an Upstream Inclined Grid with Longitudinal Bars” by C. Di Stefano and V. Ferro

The discusser would like to thank the authors of the original paper for investigating the outflow process of an upstream inclined grid with longitudinal bars using the dimensional analysis and the incomplete self-similarity theory. The discusser, however, would like to add a few points. Using the theoretical analysis the authors of the original paper showed that a power equation can be used for establishing the stage-discharge equation of an upstream inclined grid with longitudinal bars. The authors of the original paper also showed that the coefficient and exponent of the power equation depend on the slope angle and the void ratio. They proposed a stage-discharge equation

Comment on “Effects of different tillage practices on the hydraulic resistance of concentrated flow on the loess plateau in China” by J. Sun et al

Abstract For concentrated flows, which are characterized by small water depth and steep sloping beds, hydraulic conditions different from those typical of streams and rivers occur. In this study a new theoretically deduced flow resistance equation was tested using the experimental data by Sun et al. for three different tilled surfaces (Manual Dibbling, MD, Manual Hoeing, MH, and Contour Drilling, CD). At first, the profile parameter-relationship, which is the relationship between the velocity profile parameter Γ, the channel slope and the flow Froude number, was calibrated using rill flow data by Di Stefano et al. Then, the applicability of this relationship was tested by the measurements o…

Assessing flow resistance law in vegetated channels by dimensional analysis and self-similarity

Abstract In this paper experimental data collected by Kouwen et al., Wilson and Horrit, Raffaelli et al. and Carollo et al., using straight flumes having a bed covered by grass-like vegetation with different stem concentrations, were used to analyze flow resistance for flexible submerged elements. At first, the dimensional analysis and the incomplete self-similarity hypothesis was applied to deduce the flow velocity distribution and the resulting theoretical expression of the Darcy-Weisbach friction factor. Then, a relationship between the Γ function of the velocity profile and the biomechanical characteristics of vegetation, the channel slope, the Reynolds number and the flow Froude number…

Changes in Physicochemical Properties of Biochar after Addition to Soil

It is recognized that biochar undergoes changes when it is applied to soils. However, the mechanisms of biochar alterations are not fully understood yet. To this purpose, the present study is designed to investigate the transformations in the soil of two different biochars obtained from pyrolysis of fir-wood pellets. The production of the biochars differed for the dry and wet quenching procedures used to terminate the pyrolysis. Both biochars were applied to clay soil (26% sand, 6% silt, and 68% clay) placed into lysimeters. After water saturation and 15 days of equilibration, seeds of watercress (Lepidium sativum) were cultivated. After a further 7 weeks, the biochars were manually separat…

Applying Hypothesis of Self-Similarity for Flow-Resistance Law in Calabrian Gravel-Bed Rivers

In this paper, the results of an investigation carried out to test the applicability of a flow-resistance law on gravel-bed rivers in southern Italy (fiumare) are reported. First, dimensional analysis and self-similarity theory are applied for deducing the flow-resistance law (i.e., relationship among friction factor, mean velocity, shear stress, and physical properties) for gravel-bed rivers with a high boulder concentration. The proposed approach is calibrated and tested using two independent data sets (104 reaches of some Calabrian fiumare). Then, the incomplete self-similarity hypothesis is also applied to theoretically deduce the flow-velocity profile, which was integrated for obtainin…

Flume experiments for assessing the dye-tracing technique in rill flows

Abstract Flow velocity controls hillslope soil erosion and is a key hydrodynamic variable involved in sediment transport and deposition processes. The dye-tracer technique is one of the most applied methods for measuring velocity of shallow interrill and rill flow. The technique is based on the injection of a tracer in a specific point and the measurement of its speed to travel the known distance from the injection point to a given channel section. The dye-tracer technique requires that the measured surface flow velocity has to be corrected to obtain the mean flow velocity using a correction factor which is generally empirically deduced. The technique has two sources of uncertainties: i) th…

New stage-discharge relationship for inclined non-rectangular weirs

Abstract In this paper, the outflow process of inclined non-rectangular weirs is studied applying the dimensional analysis and the incomplete self-similarity theory. At first, a new stage-discharge equation, applicable for the non-rectangular weirs having a different geometrical shape (parabolic, semicircular, inverted semicircular), is theoretically deduced using a characteristic width. Then, this power stage-discharge relationship (Eq. (17) ) is calibrated and tested using measurements carried out by Raiknar for parabolic, semicircular and inverted semicircular weirs having different inclination respect to the vertical (10°, 20°, 30°, 40° and 45°). For each geometrical shape, the analysis…

Morphological Similarity of Channels: From Linear Erosional Features (Rill, Gully) to Alpine Rivers

The geometric characteristics of incised features such as channels, rills, ephemeral gully, gully, represent the erosional transport regime and the fluvial dynamic equilibrium, and thus it is critical for the understanding of the long-term evolution of natural, agricultural, and anthropogenic landscapes. This paper examines the morphological similarity of channelized erosion in two different environments such as Alpine landscapes and cultivated hillslopes. The first dataset comprises six rivers in the Italian Alps, three in the Carnia region and three in the Dolomites, where erosion is mainly the effect of discharges with high sediment loads or landslides and debris flows. The agricultural …

Regime di piena dei corsi d'acqua siciliani

Slope threshold in rill flow resistance

The applicability of a theoretical rill flow resistance equation, based on the integration of a power velocity distribution, was tested using measurements carried out in mobile and fixed bed rills, shaped on plots having different slopes (9, 14, 15, 18, 22, 24, 25 and 26%) and soil textures (clay fractions ranging from 32.7% to 73% and silt of 19.9–30.9%), and flume measurements available in the literature. The Darcy–Weisbach friction factor resulted dependent on the slope, Froude number, Reynolds number and clay and silt percentages, used as variables representative of soil transportability and detachability, respectively. This theoretical approach was applied to two different databases di…

Characterizing rainfall erosivity by kinetic power-Median volume diameter relationship

Abstract Kinetic power, i.e. kinetic energy per unit time and area, is the variable widely used to represent the rainfall erosivity which affects soil loss and sediment yield. This paper shows the results of an experimental investigation using the raindrop size distributions (DSDs) measured by an optical disdrometer installed at the Department of Agricultural, Food and Forestry Sciences of University of Palermo in Italy (June 2006–March 2014) and at the El Teularet experimental station in Spain (July 2015–May 2016). At first an analysis of the DSDs aggregated into intensity classes is carried out, then the measured kinetic power values are determined. The aggregated DSDs allowed to establis…

Flow Velocity Measurements in Vegetated Channels

Understanding of the hydraulics of flow over vegetation is very important to support the management of fluvial processes. In this paper the flow over flexible bottom vegetation is experimentally studied. A two-dimensional-acoustic doppler velocimeter is used to measure the local flow velocities for different vegetation concentrations, discharges, and flume slopes. The influence of vegetation concentration and the depth/vegetation height ratio on the measured velocity profiles is analyzed. All measured velocity distributions are S-shaped and exhibit a three-zone profile. The relationship between the velocity distribution and the turbulence intensity distribution is also analyzed. The charact…

Calibrazione di un modello distribuito per la stima della produzione di sedimenti in bacini di media estensione

Testing alternative erosivity indices to predict event soil loss from bare plots in Southern Italy

Methods for predicting unit plot soil loss for the ‘Sparacia’ Sicilian (Southern Italy) site were developed using 316 simultaneous measurements of runoff and soil loss from individual bare plots varying in length from 11 to 44 m. The event unit plot soil loss was directly proportional to an erosivity index equal to (QREI30)1·47, being QREI30 the runoff ratio (QR) times the single storm erosion index (EI30). The developed relationship represents a modified version of the USLE-M, and therefore it was named USLE-MM. By the USLE-MM, a constant erodibility coefficient was deduced for plots of different lengths, suggesting that in this case the calculated erodibility factor is representative of a…

Morphometric and hydraulic geometry assessment of a gully in SW Spain

Abstract Gully erosion represents one of the most significant types of land degradation in the Mediterranean areas, giving place to important on- and off-site effects. In this paper, a second-order gully located in SW Spain is analyzed. Along the gully, 28 cross-sections were established and measured with a Leica TCRM1102 laser total station, approximately every 6 months from 2001 to 2007. The sections were located at variable distance, placing them in areas where active erosion was evident. In total, 13 field measurements were carried out, and the geometric characteristics of 28 cross-sections were obtained. Morphometric analyses were carried out in both the main gully and a tributary reac…

INFLUENCE OF PARTICLE-SIZE DISTRIBUTION MEASUREMENT METHOD ON THE PREDICTION OF SOIL WATER RETENTION CURVE

Application of the Arya and Paris (AP) model to estimate the soil water retention curve requires detailed particle-size distributions (PSD) that can be obtained by fitting a continuous model to traditional sieve-hydrometer (SH) data or using the laser diffraction (LD) method. The AP model was applied to 40 Sicilian soils for which PSD was measured by both SH and LD methods. The scale factor  was set equal to 1.38 (procedure AP1) or estimated by a logistic model with parameters gathered from literature (procedure AP2). To simplify application of the AP model, a relationship for estimating a soil-specific  value from clay content was developed (procedure OPT). For both SH and LD data, proce…

Scala di efflusso di un misuratore "a setto centrale" in funzionamento libero

Criteri di dimensionamento delle rampe in pietrame

Measuring hydrological connectivity inside a soil by low field nuclear magnetic resonance relaxometry

Hydrological connectivity inside the soil is related to the spatial patterns inside the soil (i.e., the structural connectivity). This, in turn, is directly associated with the physical and the chemical processes at a molecular level (i.e., the functional connectivity). Nuclear magnetic resonance (NMR) relaxometry can be successfully applied to reveal both structural and functional components of soil hydrological connectivity. In the present study, the low field NMR relaxometry was applied on water suspended soils sampled at the upstream- and downstream-end of three different length plots. Also the sediments collected from the storage tanks at the end of each plot were water suspended and m…

New Stage–Discharge Relationship for Triangular Broad-Crested Weirs

Simple hydraulic structures, such as weirs, allow measuring flow discharge by using the upstream flow depth and a stage–discharge relationship. In this relationship, a discharge coefficient is introduced to correct all the effects neglected in the derivation (viscosity, surface tension, velocity head in the approach channel, flow turbulence, non-uniform velocity profile, and streamline curvature due to weir contraction). In this paper, the dimensional analysis and the incomplete self-similarity theory are used to investigate the outflow process of triangular broad-crested weirs, characterized by different values of the ratio between crest height p and channel width B, and to theoretic…

Valutazione dell'indice mensile di aggressività delle piogge in Sicilia

Closure to Discussion on “Sequent depth ratio of a B- jump” by Ohtsu and Yasuda

A theoretically-based overland flow resistance law for upland grassland habitats

Abstract Sediments conveyed from interrill areas to rills are transported by a thin flow (overland flow) and the knowledge of overland flow resistance is useful to evaluate overland flow velocity and sediment transport capacity. The aim of this paper was to verify the applicability of a theoretical overland flow resistance law, based on a power-velocity distribution, using field measurements for four upland grassland types used in different management strategies (Hay Meadows, Low-density Grazing, Rushes and Rank Grassland). Particular attention was deserved to the effects of vegetation growth cycles on the surface roughness and the corresponding reduction of overland flow velocity. The rela…

Una nuova formulazione del risalto idraulico

EFFETTI DELLA PENDENZA PARCELLARE SULLA PERDITA DI SUOLO STIMATA CON LA USLE-MM

La USLE-MM è un modello previsionale della perdita di suolo alla scala dell’evento erosivo che introduce il coefficiente di deflusso parcellare nel set di variabili indipendenti della USLE e consente la previsione di una perdita di suolo per unità di superficie non necessariamente crescente con la lunghezza della pendice. Tale circostanza, che la USLE non è in grado di riprodurre, è stata ampiamente riscontrata in letteratura e nell’area sperimentale di Sparacia. Il fattore climatico della USLE-MM è pari ad una potenza del prodotto del coefficiente di deflusso per l’indice di aggressività della pioggia di Wischmeier e Smith (1978). Il modello USLE–MM è stato originariamente dedotto facendo …

Testing assumptions and procedures to empirically predict bare plot soil loss in a Mediterranean environment

Empirical prediction of soil erosion has both scientific and practical importance. This investigation tested USLE and USLE-based procedures to predict bare plot soil loss at the Sparacia area, in Sicily. Event soil loss per unit area, Ae, did not vary appreciably with plot length, λ, because the decrease in runoff with λ was offset by an increase in sediment concentration. Slope steepness, s, had a positive effective on Ae, and this result was associated with a runoff coefficient that did not vary appreciably with s and a sediment concentration generally increasing with s. Plot steepness did not have a statistically detectable effect on the calculations of the soil erodibility factor of bot…

Briglie con savanella a profilo W

Statistical check of USLE-M and USLE-MM to predict bare plot soil loss in two Italian environments

The USLE-M and the USLE-MM estimate event plot soil loss. In both models, the erosivity term is given by the runoff coefficient, QR, times the single-storm erosion index, EI30. In the USLE-MM, QREI30is raised to an exponent b1> 1 whereas b1= 1 is assumed in the USLE-M. Simple linear regression analysis can be applied to parameterize both models, but logarithmically transformed data have to be used for USLE-MM. Parameterizing the USLE-MM with nonlinear regression of untransformed data could be a more appropriate procedure. A statistical check of the two suggested models (USLE-M and USLE-MM), considering two alternative parameterization procedures for the USLE-MM, was carried out for the Mass…

Discussion of “Three Simple Flumes for Flow Measurement in Open Channels” by Zohrab Samani

In this paper the results on three simple flumes for flow measurements are discussed.

Predicting event soil loss from bare plots at two Italian sites

Abstract Including runoff in USLE-type empirical models is expected to improve plot soil loss prediction at the event temporal scale and literature yields encouraging signs of the possibility to simply estimate runoff at these spatial and temporal scales. The objective of this paper was to develop an estimating procedure of event soil loss from bare plots (length = 11–44 m, slope steepness = 14.9–16.0%) at two Italian sites, i.e. Masse, in Umbria, and Sparacia, in Sicily, having a similar sand content (5–7%) but different silt (33% at Sparacia, 59% at Masse) and clay (62% and 34%, respectively) contents. A test of alternative erosivity indices for the Masse station showed that the best perf…

Indagini sulla stima della produzione di sedimenti mediante l'impiego della tecnica del cesio-137. Il caso del torrente Trionto in provincia di Cosenza

Sperimentazione di laboratorio e di pieno campo sull'impiego delle soglie in legname e pietrame.

Sperimentazione di laboratorio sulle soglie in massi

CARATTERISTICHE DIMENSIONALI ED ENERGETICHE DI PRECIPITAZIONI NATURALI MISURATE CON UNA TECNICA DISDROMETRICA IN SPAGNA

Nella memoria sono riportati i risultati ottenuti a partire dalle distribuzioni dimensionali delle gocce di pioggia (DSD) rilevate nel periodo Luglio 2015- Gennaio 2016, mediante un disdrometro ottico installato presso la stazione sperimentale “El Teularet- Sierra de Enguera” sita nella comunità Valenciana. Dopo aver aggregato le DSD per classi di intensità, è stata condotta una analisi sulle caratteristiche delle distribuzioni rilevate in funzione dell’intensità di precipitazione ed è stata verificata l’applicabilità della distribuzione di Ulbrich utilizzando il metodo dei momenti per la stima dei parametri. Le misure sono state utilizzate per determinare i valori misurati di potenza cinet…

Field investigation on rilling in the experimental Sparacia area

In this paper the results of a field investigation on rilling carried out in the experimental Sparacia area are reported. The measurements were made on a plot 6 m wide and 22 m long subjected to natural rainfalls. For ten rainfalls the total soil loss (interrill and rill erosion) was collected in a storage system consisting of two tanks arranged in series at the base of the plot. Rill morphology (rill length and cross-sections) was measured for five rainfall events, while the rill profile was surveyed for three events. First the contribution of each component (rill and interrill erosion) to total soil loss was established. Then the analysis allowed establishment of a power relationship betw…

Testing a new rill flow resistance approach using the Water Erosion Prediction Project experimental database

In this paper, a recently theoretically deduced rill flow resistance equation, based on a power‐velocity profile, was tested using the Water Erosion Prediction Project database. This database includes measurements of flow velocity, water depth, cross section area, wetted perimeter, and bed slope that were made in rills shaped on experimental sites distributed across the continental United States. In particular, three different experimental conditions (only rainfall, only flow, and rain with flow) were examined, and for each condition, the theoretically based relationship for estimating the Γ function of the power velocity profile was calibrated. The results established that (a) the Darcy‐We…

Sulla geometria idraulica dei rill e degli ephemeral gully rilevati a Sparacia, in Sicilia

Flow velocity and turbulence intensity distribution in a vegetated straigth laboratory channel

Una nuova stazione sperimentale per il monitoraggio della produzione di sedimenti nell'area sperimentale di Sparacia

Estimating soil loss of given return period by USLE-M-type models

Many field investigations have clearly shown that rare and severe events control total soil erosion occurring over a long time period with up to 92% of total soil erosion over a 7‐year period resulting from just three daily events. Therefore, soil conservation strategies should be developed taking into account large events rather than long‐term average erosion. From an engineering point of view, establishing the soil loss of a given return period is needed. This can be obtained by the frequency analysis of soil loss measurements or by suitable soil erosion models. The USLE‐M modified and USLE‐M based are two empirical Universal Soil Loss Equation‐Modified (USLE‐M) type models which were dev…

La valutazione delle piene in Sicilia. L'esperienza del progetto VAPI

Riqualificazione ambientale dei corsi d'acqua

Applicazione della USLE-MM per la stima distribuita della produzione di sedimenti

Assessing, measuring and modelling erosion in calanchi areas: A review

Calanchi are erosion landforms characterised by a heavily dissected terrain with steep, unvegetated slopes and channels with a dendritic pattern, which rapidly incise and extend headwards. Recent literature focusing on badland systems highlights their similarity with other larger fluvial landforms, stating that these behave as a full size laboratory, due to their rapid development in space and time and to the diversity of geomorphic processes involved. In this paper, a brief review of the most important results on badland research is firstly presented. Then, the morphometric similarity between calanchi and other erosion landforms is discussed. Finally, models quantitatively relating the vol…

Elaboración de modelos 3D de diferentes morfologías y escalas utilizando técnicas Structure-from-Motion y fotografías terrestres

En este trabajo se evalúan los métodos de foto-reconstrucción automatizada basados en el uso conjunto de las técnicas Structure from Motion (SfM) y Multi-View Stereo (MVS) para medir, monitorizar y cuantificar la dinámica de tres formas geomorfológicas: i) el glaciar rocoso del Corral del Veleta (Granada, España), ii) un paisaje de cárcavas de tipo calanchi (Sicilia, Italia) y ii) cinco pequeñas cabeceras de cárcava (Cáceres, España). Se incluyen en este trabajo los resultados sobre la precisión, utilidad y aplicabilidad de estas técnicas. Para la cuantificación de la precisión se utilizan el error cuadrático medio (RMSE) de los puntos de control que se emplean en la georreferenciación y la…

Valutazione delle altezze coniugate per un risalto idraulico tipo B-jump

Estimating rainfall erosivity by aggregated drop size distributions

Rainfall erosivity is defined as the potential of the rain to cause erosion, and it can be represented by rainfall kinetic power. At first in this paper, the raindrop size distributions (DSD) measured by an optical disdrometer located at Palermo in the period June 2006–March 2014 and aggregated for intensity classes, are presented. Then an analysis of raindrop size characteristics is carried out, and the reliability of Ulbrich's distribution, using both the maximum likelihood and momentum estimate parameter methods, is tested. The raindrop size measurements are used to determine the experimental rainfall kinetic power values, which are compared with the ones calculated by a theoretically de…

Elementi di difesa dei versanti

Measuring the USLE soil erodibility factor in the unit plots of Sparacia (southern Italy) experimental area

The Universal Soil Loss Equation (USLE) is still widely used to predict soil loss by water erosion and to establish soil conservation measures. In this model, the soil erodibility factor K accounts for the susceptibility of the soil to be eroded due to the detachment and transport processes operated by the erosive agents. According to the USLE scheme, the K factor should be measured on unit plots, i.e., bare plots of given length (22 m) and steepness (9%) tilled along the maximum slope direction, but there is little evidence that there ever existed an actual unit plot between the plots used to develop the USLE. Given the difficulty in collecting sufficient data to adequately measure K, the …

Measuring rill erosion at plot scale by a drone-based technology

The traditional direct method (i.e. metric ruler and rillmeter) of monitoring rill erosion at plot scale is time consuming and invasive since it modifies the surface of the rilled area. Measuring rill features using a drone-based technology is considered a non-invasive method allowing a fast field relief. In the experimental Sparacia area a survey by a quadricopter Microdones md4-200 was carried out and this relief allowed the generation of a Digital Elevation Model (DEM), with a mesh size of 1 cm and a resolution elevation equal to 2 mm, for three plots (L, G and C) affected by rill erosion. At first for the experimental L plot, which is 44 m long, the rill features were surveyed by a “man…

Zonizzazione climatica del territorio siciliano per la determinazione delle aree sensibili alla desertificazione

Sediment Delivery Distributed (SEDD) Model

Because eroded sediments are produced from different sources throughout a basin, it is often advantageous to model sediment delivery processes at basin scale using a spatially distributed approach....

Testing a new sampler for measuring plot soil loss

In order to measure soil loss in equipped plots the estimate of the weight of solid material intercepted at their lower end is required. At the experimental area of Sparacia, Sicily, the runoff produced by an erosive event is collected within storage tanks with a capacity of about 1m3. In this paper, the use of a new sampler is proposed to measure easily the weight of solid material eroded from an experimental plot and collected into a storage tank. The sampler is a cylinder having a closing valve at the bottom. Two different series of runs were carried out both to test the reliability of the sampler and to establish a sampling procedure, respectively. An analysis of various sampling config…

Experimental study of boulder concentration effect on flow resistance in gravel bed channels

Abstract Previous studies demonstrated that for open channel flows the power velocity profile can be integrated to obtain the flow resistance law. In this paper the relationship between Γ coefficient of the power velocity distribution, the channel slope and Froude number (Eq. (9) ) is firstly presented. Then the measurements carried out in a laboratory flume covered by hemispheric elements for two different hydraulic conditions (partially inundated and inundated) are used to calibrate this relationship. These elements are placed with a square arrangement and have a concentration range 4–64%. For the two investigated hydraulic conditions, this analysis demonstrates that the relationship to e…

A method for evaluating rainfall kinetic power by a characteristic drop diameter

Abstract Empirical relationships linking kinetic energy to rainfall intensity are commonly used to estimate rainfall erosivity. In this paper, using the drop-size distribution (DSD) proposed by Marshall and Palmer, a relationship for calculating the rainfall kinetic power was firstly deduced. This equation requires the simultaneous measurement of both the median volume diameter and the rainfall intensity and its application also reveals the drawback of needing the measurement of the whole DSD by an expensive disdrometric technique. Then, using a fictitious precipitation, which is both constituted by droplets having the same diameter (mean volume diameter) and having the same volume of the a…

La difesa del suolo in mabito montano: le sistemazioni idraulico-forestali sono ancora una risposta adeguata ?

L’Italia è costantemente afflitta da catastrofi di origine idrogeologica, nell’immediato seguito delle quali molti avanzano prontamente ricette e soluzioni “definitive” per poi dimenticarsene altrettanto rapidamente. Le Sistemazioni Idraulico-Forestali (SIF) da oltre un secolo hanno giocato e continuano a giocare un ruolo fondamentale per garantire la sicurezza dei territori montani e collinari, ma in molte parti del nostro Paese ciò sembra essere stato dimenticato. Nella memoria gli Autori si pongono la domanda se le SIF siano davvero ancora attuali ed indispensabili in una società che è profondamente mutata rispetto ai decenni che le hanno viste protagoniste. La risposta che danno è posit…

Morphological characteristics of ephemeral gullies in Sicily, south Italy

Ephemeral gullies (EGs) are channels of different sizes refilled by tillage equipment normally used on farms. In this paper, the data-set collected from 1995 to 2007 in a wheat-cultivated area in Raddusa (Sicily, Italy), having a surface of almost 80 ha, were used to analyze the morphological characteristics of EGs. The measurements show an high temporal variability in EG characteristics. The EG measurements and the rill erosion measurements carried out in 15 plots located in the experimental “Sparacia” area (Sicily), demonstrated that a morphological similarity condition exists between rills and ephemeral gullies. The occurrence of step-pool structures in an EG occurring in the observation…

Il misuratore di portata a cilindri (BF): indagine sperimentale e verifica di campo

New Expression of the Hydraulic Jump Roller Length

AbstractThis paper presents the results of an experimental investigation on the roller length of both classical and B-jumps on smooth beds. Using the measurements conducted in this investigation and those available in the literature, a new relationship is proposed for estimating the roller length of classical and B-jumps on smooth beds. Finally, it is demonstrated that the proposed equation is also applicable to estimate the roller length of hydraulic jumps on rough horizontal beds.

Sulla formazione di un profilo di velocità S-shaped in condizioni di macro-scabrezza

Closure to “Analyzing Turbulence Intensity in Gravel Bed Channels” by F. G. Carollo, V. Ferro, and D. Termini

Analysis of soil loss data from plots of differing length for the Sparacia experimental area, Sicily, Italy

Widely used models of the soil erosion process, such as the empirical universal soil loss equation (USLE) and revised USLE (RUSLE), suggest that soil loss, i.e. the mass of soil lost by water erosion per unit surface area, increases with slope length, λ, although contrasting experimental results may be found in the literature. Experiments were carried out at the Sparacia site, Sicily, to establish the influence of plot length on soil loss. This was tested using data characterised by a high number of replicated, bare plots of different lengths (0.25, 0.4, 1, 2, 5, 11, 22, 33 and 44 m), simultaneously operating in the 1999–2008 period. Event soil losses did not vary significantly with λ or ev…

UN NUOVO MODELLO PER LA STIMA DELL’ERODIBILITÀ RILL

Molti modelli process-oriented per la previsione dell’erosione rill utilizzano parametri, come l’erodibilità rill, che sono specifici del sito di interesse e pertanto l’applicazione dei suddetti modelli necessita la misura di questi parametri o una loro stima indiretta. L’obiettivo del presente lavoro è quello di proporre un metodo per la misura indiretta dell’erodibilità rill del suolo dell’area sperimentale di Sparacia, in Sicilia. Sono state utilizzate le misure condotte sui rill rilevati nelle parcelle di Sparacia in occasione di sette eventi di pioggia naturale e un semplice approccio matematico basato sull’equazione che simula il distacco dei sedimenti tenendo conto della variabilità …

Morphometric analysis of calanchi areas by low-altitude flight

Un nuovo modello distribuito per la stima della produzione di sedimenti

Dimensional analysis and stage-discharge relationship for weirs: a review

Deducing the weir flow stage-discharge relationship is a classical hydraulic problem. In this regard Buckingham’s theorem of dimensional analysis can be used to find simple and accurate formulas to obtain the rating curves of different weir types. At first, in this review paper the rectangular weir that is a very common hydraulic structure is studied. It is indicated that the crest shape, approach channel width, obliquity (angle between the weir crest and the direction normal to the flow motion) and vertical inclination (pivot weir) are the key-parameters affecting the flow over the rectangular weirs. The flow over the triangular, labyrinth, parabolic, circular, elliptical, and W-weirs are …

La lunghezza del roller del risalto idraulico

Analyzing turbulence in gravel bed channels

In this paper, the results of an experimental investigation of the turbulence intensity in gravel bed channels are described. The runs were carried out by measuring, with an acoustic Doppler velocimeter, the turbulence intensity profile along six verticals of a given cross section in a laboratory flume. The analysis of the measured intensity distributions has shown the existence of two different regions, above and below the tops of the roughness elements, in which different intensity profiles occur. Furthermore, the measured profiles have shown a maximum of the turbulence intensity that decreases for increasing values of the roughness height, confirming that the turbulence damping efficienc…

A new empirical model for estimating calanchi Erosion in Sicily, Italy

Abstract Calanchi (plural of calanco) are typical badland landforms of the Italian landscape. They consist of dense networks of V-shaped valleys, with a sparse or absent vegetation cover, which frequently develop on unconsolidated or poorly consolidated clayey deposits. In this paper, the dimensional analysis and the incomplete self-similarity theory were used to deduce a model relating the volume of sediments eroded from the calanchi area to a set of geometric attributes of their tributary areas. The morphometric characteristics of 209 calanchi basins were used to calibrate and validate the model. The predictive skill of the model was assessed by calculating the mean square error and the N…

Assessing Stage-Discharge Relationships for Circular Overflow Structure

Circular overflow structures are used in irrigation and drainage networks as water measuring structures. Different approaches can be found in the literature to formulate the stage-discharge relationship of the circular weir. They are mainly categorized in three groups: (1)methods trying to simplify the complex elliptic integrals coming from the theoretical discharge equation; (2)methods that use the orifice formula and a discharge coefficient specific for the circular weir; and (3)approaches using dimensional analysis and Buckingham's Theorem. In this study, a nondimensional stage-discharge formula was obtained using Buckingham's Theorem to define the flow over the sharp-crested circular we…

Short-duration rainfalls in Sicily

The Italian Hydrographic Service publishes yearly maximum rainfall depths with 1-, 3-, 6-, 12-, and 24-hr duration, recorded by recording rain gauges. It also publishes selected short-duration (t<1 hr) rainfall amounts. It is impossible to carry out a statistical analysis of the short-duration rainfalls for each recording rain gauge because the published data correspond to different record durations and to different recording rain gauges from year to year. Therefore, there is a practical need to derive empirical relationships between the 1-, 3-, 6-, 12-, and 24-hr duration amounts and shorter duration (t<1 hr) rainfall amounts. Such a relationship has been proposed by Bell and has been veri…

Verifica del modello SEDD per bacini siciliani di grande estensione

Monitoraggio della perdita di suolo a differenti scale spaziali nell'area di Sparacia

Flow and turbulence characteristics in a vegetated straigth flume

Stima della potenza cinetica della precipitazione a partire da osservazioni disdrometriche di distribuzioni dimensionali delle gocce di pioggia

Lo studio del distacco delle particelle di suolo operato dalla pioggia richiede la conoscenza delle caratteristiche erosive della precipitazione. Nella memoria, dopo aver richiamato i presupposti teorici della legge di Ulbrich e le espressioni della potenza cinetica da essa deducibili, viene presentata una verifica di applicabilita della suddetta distribuzione teorica sulla base delle distribuzioni dimensionali delle gocce di pioggia rilevate mediante un disdrometro ottico installato presso la sezione Idraulica del Dipartimento dei Sistemi Agro-Ambientali dell’Universita di Palermo. Viene proposta, infine, una verifica sperimentale dell’equazione di Wischmeier e Smith per il calcolo della p…

Comments on “Overflow characteristics of streamlined weirs based on model experimentation” by Bagheri S. and Kabiri-Samani A

Abstract In this paper the stage-discharge equation of a streamlined weir is theoretically deduced applying the Π-Theorem of dimensional analysis and the self-similarity theory. The coefficients of the new stage-discharge relationship are estimated using the experimental results by Bagheri and Kabiri-Samani.

Sediment delivery processes and chemical transport in a small forested basin

Recent reaserch has directed attention to the properties of the eroded material because of its influence in deposition phenomena and in carrying capacity of pollutant materials

Testing the Outflow Process over a Triangular Labyrinth Weir

In this paper, the dimensionless stage-discharge relation for a sharp-crested triangular labyrinth weir, determined in a previous study, is initially tested by some experimental runs carried out in a laboratory flume. According to this relationship, the flow magnification is affected by the length-magnification ratio and the head to one cycle width ratio. The measurements allowed to test the applicability of this dimensionless relation for different values of both the angle of the sidewall to the main flow direction and the weir height. Finally, the proposed dimensionless equation was also tested by using experimental measurements carried out for broad-crested triangular labyrinth weir.

Flow resistance equation for rills

In this paper, a new flow resistance equation for rill flow was deduced applying dimensional analysis and self‐similarity theory. At first, the incomplete self‐similarity hypothesis was used for establishing the flow velocity distribution whose integration gives the theoretical expression of the Darcy–Weisbach friction factor. Then the deduced theoretical resistance equation was tested by some measurements of flow velocity, water depth, cross section area, wetted perimeter, and bed slope carried out in 106 reaches of some rills shaped on an experimental plot. A relationship between the velocity profile, the channel slope, and the flow Froude number was also established. The analysis showed …

Erratum for “Experimental Modeling of Submerged Pivot Weir” by M. Bijankhan and V. Ferro

Predicting rainfall erosivity by momentum and kinetic energy in Mediterranean environment

Abstract Rainfall erosivity is an index that describes the power of rainfall to cause soil erosion and it is used around the world for assessing and predicting soil loss on agricultural lands. Erosivity can be represented in terms of both rainfall momentum and kinetic energy, both calculated per unit time and area. Contrasting results on the representativeness of these two variables are available: some authors stated that momentum and kinetic energy are practically interchangeable in soil loss estimation while other found that kinetic energy is the most suitable expression of rainfall erosivity. The direct and continuous measurements of momentum and kinetic energy by a disdrometer allow als…

Cover and Management Factor for Sicilian Vineyard Systems

VERIFICA DI UNA TECNICA FOTOGRAFICA PER IL RILIEVO DELLA GEOMETRIA DI UN CANALE IN TERRA

Nella memoria sono riportati i risultati delle verifiche di applicabilità di una tecnica image-based per il monitoraggio dei processi di erosione canalizzata. L’indagine, in particolare, ha avuto lo scopo di testare l’uso di modelli tridimensionali del terreno (DTM) ottenuti con l’impiego di un numero elevato di fotografie della stessa scena acquisite da differenti punti di vista (Tecnica “Structure-From Motion” SFM e “Multi-View-Stereo MVS). Il DTM tridimensionale (3D) è stato generato utilizzando il software open source Autodesk 123D Catch mentre per la creazione del Digital Elevation Model DEM (2.5D) è stato impiegato il software CloudCompare. Dei due canali in terra utilizzati nella spe…

Rilievo di un ephemeral gully nell’area sperimentale di Sparacia mediante una tecnica fotografica

Nella memoria sono riportati i risultati dell’applicazione di una tecnica imagebased per il monitoraggio di un ephemeral gully formatosi nel gennaio 2015 nell’area sperimentale di Sparacia. Nel gully, lungo 54 m, sono state individuate 24 sezioni trasversali che sono state rilevate in campo mediante l’uso di un profilometro. L’indagine ha inoltre previsto la realizzazione di un modello tridimensionale del terreno (DTM) ottenuto con l’impiego di un numero elevato di fotografie della stessa scena acquisite da differenti punti di vista (Tecnica “Structure-From Motion” SFM e “Multi-View-Stereo MVS). Dal DTM tridimensionale (3D) e dal modello 2.5D sono stati estratti i profili delle sezioni tras…

Verifica della USLE-MM per il bacino sperimentale SPA2 in Sicilia

Flow resistance in gravel-bed channels with large-scale roughness

A previously published mixing length (ML) model for evaluating the Darcy–Weisbach friction factor for a large-scale roughness condition (depth to sediment height ratio ranging from 1 to 4) is briefly reviewed and modified (MML). Then the MML model and a modified drag (MD) model are experimentally tested using laboratory measurements carried out for gravel-bed channels and large-scale roughness condition. This analysis showed that the MML gives accurate estimates of the Darcy–Weisbach coefficient and for Froude number values greater than 0·5 the MML model coincides with the ML one. Testing of the MD model shows limited accuracy in estimating flow resistance. Finally, the MML and MD models are com…

Estimating rainfall erosivity by aggregated drop size distributions

Rainfall erosivity is defined as the potential of the rain to cause erosion, and it can be represented by rainfall kinetic power. At first in this paper, the raindrop size distributions (DSD) measured by an optical disdrometer located at Palermo in the period June 2006–March 2014 and aggregated for intensity classes, are presented. Then an analysis of raindrop size characteristics is carried out, and the reliability of Ulbrich's distribution, using both the maximum likelihood and momentum estimate parameter methods, is tested. The raindrop size measurements are used to determine the experimental rainfall kinetic power values, which are compared with the ones calculated by a theoretically de…

Evaluation of the SEDD model for predicting sediment yield at the Sicilian experimental SPA2 basin

In this paper a spatially distributed model of the hillslope sediment delivery processes, named the sediment delivery distributed (SEDD) model, is initially reviewed; the model takes into account the sediment delivery processes due to both the hillslope sediment transport and the effects of slope curvature. Then the rainfall and sediment yield events measured at the experimental SPA2 basin, in Sicily, are used both to calibrate the SEDD model and to verify the predictive capability of the distributed sediment delivery approach at event scale. For the SPA2 basin discretized into morphological units and stream tubes, the SEDD model is calibrated at event scale using the measurements carried o…

Discussion of “Simple Flume for Flow Measurement in Open Channel” by Zohrab Samani and Henry Magallanez

This paper is a Discussion of “simple flume for flow measurement in open channel".

Field investigation of rill and ephemeral gully erosion in the Sparacia experimental area, South Italy

Abstract This paper reports the results of a field investigation aiming at characterizing the morphology and hydraulics of both rills and ephemeral gullies (EGs) monitored at Sparacia experimental area, Sicily, Italy. The comparison between rill and interrill erosion measurements showed that sediment delivery processes occurred in some erosive events and that the rill erosion rate was dominant in many cases. The measurements were used for testing both the empirical relationships between the channel (rill, EGs and gully) length and its eroded volume and among the morphological variables (length, width, depth and volume) describing the channelized process. Finally, the rill and EGs hydraulic …

Recenti acquisizioni nel settore delle sistemazioni idraulico-forestali

Measurement of Water Soil Erosion at Sparacia Experimental Area (Southern Italy): A Summary of More than Twenty Years of Scientific Activity

The main purpose of this article is to give a general idea of the scientific activity that was carried out starting from the 2000s on the basis of the data collected in the plots installed at the Sparacia experimental station for soil erosion measurement in Sicily, South Italy. The paper includes a presentation of the experimental site, a description of the methods and procedures for measuring soil erosion processes both available in the literature and applied at the Sparacia station (sediment sampling and water level reading in the storage tanks for total erosion measurements; profilometer, and Structure from Motion technique for rill erosion measurements), and the main results obtained in…

Influenza della tecnica di misura della distribuzione granulometrica sulla stima della curva di ritenzione idrica del suolo

Le distribuzioni granulometriche ottenute sia con il tradizionale metodo per stacciatura-sedimentazione (SH) che con il metodo della diffrattometria laser (LD) sono state utilizzate per determinare le curve di ritenzione idrica di 40 suoli siciliani attraverso modello di Arya e Paris (AP). La curve di ritenzione idrica determinate con il metodo SH sono risultate più accurate di quelle ottenute dal metodo LD. Fra le differenti procedure applicative utilizzate, i risultati migliori si sono ottenuti utilizzando per ciascun suolo un valore del parametro  determinato attraverso una procedura di ottimizzazione. Infine, è stata proposta una relazione tra il parametro  e il contenuto in argilla c…

Briglie a fessura

Una nuova installazione sperimentale per la misura delle caratteristiche energetiche della precipitazione e della perdita di suolo parcellare

New Theoretical Solution of the Stage-Discharge Relationship for Sharp-Crested and Broad Weirs

In this paper, the outflow process of a sharp-crested and broad weir is studied using the dimensional analysis and the incomplete self-similarity theory. The new stage discharge is theoretically deduced and its testing is carried out using measurements both available in literature and obtained by laboratory runs carried out in this investigation.

Contributo allo studio della lunghezza del risalto libero su fondo liscio e scabro

Testing mechanical characteristics of chestnut stakes used in bed sills for stream restoration

Using of wood elements for constructing bed sills in Mediterranean streams, where the banks are not protected by tree vegetation, needs an evaluation of biological and mechanical characteristics for evaluating both the wood durability and the effectiveness of the stream restoration project. Very few studies have dealt both with the decay of mechanical characteristics of wood elements employed for stream restoration works and with the changes over time of physical and chemical wood characters. In this paper, for a wood and stone bed sill located in a stream having no shaded banks, the changes of physical and chemical characters detected after 12, 18, 24, 30, 36, 42 and 48 months on chestnut …

Identifying a dominant discharge for natural rivers in southern Italy

Abstract Natural rivers are subjected to continuous adjustments in response to any change in the environment. These environmental changes may occur naturally, as in the case of climatic variation or changes in vegetative cover, or may be related to human activities including channelization, damming, bank protection, and bridge construction. Identifying the value of that discharge (‘dominant’ or ‘effective’ discharge, QD) considered responsible for the main changes operated by a river has been a subject of great challenge to scientists and engineers during the last decades. In fact, this threshold value is largely adopted for stream-management decisions, for predicting the stable slope upstr…

Modellazione della produzione di sedimenti nel bacino sperimentale SPA2 in Sicilia

Reliability of rainfall kinetic power-intensity relationships

The rainfall erosivity plays a fundamental role in water soil erosion processes and it can be expressed by its kinetic power. At first in this paper the raindrop size distributions measured, in the period June 2006- March 2014, by an optical disdrometer installed at the Department of Agricultural and Forestry Sciences of University of Palermo are aggregated into rainfall intensity classes, having different ranges, and the measured kinetic power values are determined. Measured kinetic power values are initially used for testing the applicability of the kinetic power-rainfall intensity relationships proposed by Wischmeier and Smith (1978), used in Universal Soil Loss Equation (USLE), Brown an…

Hydraulic jumps on rough beds

This paper presents the results of an experimental investigation on the hydraulic jump on horizontal rough beds. Experiments were carried out to study the effect of bed roughness on both the sequent depth ratio and the roller length. The investigation allowed the writers to positively test the reliability of a new solution of the momentum equation for the sequent depth ratio as a function of the Froude number and the ratio between the roughness height and the upstream supercritical flow depth. The applicability of some empirical relationships for estimating the roller length was also tested.

New Theoretical Solution of Stage-Discharge Relationship for Slit Weirs

In this paper, the flow-process of a slit weir was analyzed on the basis of a theorem of dimensional analysis and incomplete selfsimilarity theory. The theoretically deduced stage-discharge formula then was calibrated using experimental data obtained for a ratio between the weir and the channel width, ranging from 0.05 to 0.25. The deduced stage-discharge relationship allowed measuring discharge values characterized by errors that, for 98% of the measured values, were less than or equal to 5%. The performance of the proposed theoreticalstage-discharge formula also was improved by introducing the Reynolds number (for 98.5% of the measured values the error was less than or equal to 5%, and th…

Caratteri energetici dedotti dalle distribuzioni dimensionali delle gocce di pioggia rilevate mediante un disdrometro ottico

SW—Soil and Water

Abstract Recent research has directed attention to the size distribution of eroded material because of its influence on deposition mechanics and in carrying capacity of pollutant materials. At first, in this paper the relationship between aggregate breakdown mechanism and erosion processes is briefly reviewed. Then the link between the clay enrichment ratio and the sediment delivery ratio at morphological unit scale is investigated. For 129 soil samples well distributed over the Sicilian Sparacia basin, the values for the experimental clay enrichment ratio calculated by the measured ultimate grain-size distributions are compared with the theoretical clay enrichment ratio values obtained by …

Resistenze al moto di correnti in canali con vegetazione sul fondo

Monitoraggio della produzione di sedimenti e calibrazione di un modello distribuito in un piccolo bacino forestato

Confronto della perdita di suolo da parcelle di differente lunghezza nell'area di Sparacia

Opere di sistemazione idraulico forestale a basso impatto ambientale