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.

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

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.

Processo di efflusso da uno stramazzo a profilo W

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

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

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

Interventi di riqualificazione fluviale del tratto terminale del torrente Petrolo

Closure to "Analyzing turbulence intensity in gravel bed channel"

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…

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

Testing a new sampler for measuring plot soil loss

Experimental investigation of the outflow process over a triangular labyrinth weir

Analisi sperimentale del risalto idraulico su fondo orizzontale scabro

Determinazione delle altezze coniugate del B-jump su fondo scabro

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 …

Esperienze sull'efflusso da uno sfioratore a profilo W

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…

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…

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…

Processi dissipativi su rampe in pietrame a differente granulometria

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

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

Verifica sperimentale di un campionatore per la misura della perdita di suolo

Per la misura di perdita in suolo in parcelle attrezzate è necessaria la stima del peso del materiale solido intercettato nella loro sezione terminale. Nell’area sperimentale di Sparacia, i deflussi torbidi prodotti in seguito ad un evento erosivo vengono convogliati all’interno di vasche di accumulo della capacità di circa 1 m3. Nella memoria per misurare agevolmente il peso di materiale solido eroso da una parcella si propone l’estrazione di campioni rappresentativi della miscela torbida presente in ciascuna vasca facendo uso di un nuovo campionatore appositamente predisposto. La verifica di funzionamento del campionatore è stata condotta effettuando due distinte seri di prove finalizzate…

Testing the Stage-Discharge Relationship in Sloping SMBF Flumes

The Samani, Magallanez, Baiamonte, Ferro (SMBF) flume is a simple and inexpensive instrument for indirect discharge measurement that was originally proposed for use in a horizontal channel and then also applied in sloping channels. The contraction of the flow cross section, aimed at establishing a critical flow condition, is simply obtained by applying two half cylinders to the walls of a rectangular cross section. In this paper a theoretical approach previously proposed for a horizontal SMBF flume is first extended to a sloping SMBF flume and a new stage-discharge relationship is deduced. Then, this equation is experimentally tested using laboratory measurements from literature for differe…

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

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.

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

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…

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

Monitoraggio dell'erosione rill con rilievo aereo di bassa quota

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…

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-…

Analisi delle distribuzioni dimensionali delle gocce di pioggia rilevate in Sicilia

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

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

Rilievi del profilo di velocità in un canale con vegetazione sommersa

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…

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

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

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.

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…

Closure to “Testing the Stage-Discharge Relationship in Sloping SMBF Flumes” by Francesco Giuseppe Carollo and Vincenzo Pampalone

This is the closure to the discussions on the paper "Testing the Stage-Discharge Relationship in Sloping SMBF Flumes".

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…

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

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…

Un nuovo campionatore per la misura della perdita di suolo in parcelle attrezzate

Le misure di perdita di suolo in parcelle attrezzate necessitano la conoscenza del peso del materiale eroso intercettato nella sezione terminale delle parcelle. Nell’area sperimentale di Sparacia attrezzata per la misura della perdita di suolo i deflussi torbidi prodotti in seguito ad un evento erosivo vengono convogliati mediante una grondaia posta a valle di ciascuna parcella all’interno di vasche di accumulo. Per misurare la frazione di materiale solido presente nel volume della sospensione raccolto in dette vasche, si propone l’utilizzo di un nuovo campionatore appositamente predisposto. Esso consiste in un cilindro di ottone, di noto diametro, dotato nella sezione terminale di una valv…

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

Experimental investigation of flow characteristics in vegetated channels

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.

Studio sperimentale del risalto idraulico su fondo liscio orizzontale e pendente

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 …

Sul dimensionamento delle rampe in pietrame

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…

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…

Criteri di dimensionamento delle rampe in pietrame

Theoretical prediction of rainfall intensity for a small rainfall simulator

In this contribution, a theoretical approach was developed for predicting rainfall intensity for a small rainfall simulator. The developed equation was tested for two different devices and different pressure head and water temperature values. The proposed relationship was found to have a good predictive ability of rainfall intensity. The proposed theoretical approach could be usable with other devices that operate on the same principles of the simulator considered in this investigation.

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…

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

Una nuova formulazione del risalto idraulico

Briglie con savanella a profilo W

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…

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

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…

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…

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…

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

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…

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.

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.

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…

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…

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…

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

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

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.

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

Resistenze al moto di correnti in canali con vegetazione sul fondo