Analisi dell’influenza della risoluzione spaziale di un TIN sulla risposta idrologica a scala di bacino

Modelling of Rainfall Induced Landslides in Puerto Rico

Exploiting historical rainfall and landslide data in a spatial database for the derivation of critical rainfall thresholds

Critical rainfall thresholds for landslides are powerful tools for preventing landslide hazard. The thresholds are commonly estimated empirically starting from rainfall events that triggered landslides in the past. The creation of the appropriate rainfall–landslide database is one of the main efforts in this approach. In fact, an accurate agreement between the landslide and rainfall information, in terms of location and timing, is essential in order to correctly estimate the rainfall–landslide relationships. A further issue is taking into account the average moisture conditions prior the triggering event, which reasonably may be crucial in determining the sufficient amount of precipitation.…

Sviluppo di un sistema di monitoraggio per lo studio delle dinamiche meteorologiche nell'area urbana di Palermo.'

A Comparison between Heuristic, Statistical and Data-driven Methods in Landslide Susceptibility Assessment: an Application to the Briga and Giampilieri Catchments

Susceptibility assessment concerning the estimation of areas prone to landslide is one of the most useful approach in the analysis of landslide hazard. Over the last years, in an attempt to find the best approach to evaluate landslide susceptibility, many methods have been developed. Among these, the heuristic, the statistical, and the data-driven approaches are very widespread, and they all are based on the concept that the conditions which led to landslide movements in the past will control the probability of movement occurrence in the future. This study presents an assessment of landslide susceptibility in which models of the three different methodologies, such as the heuristic approach,…

Elaborazione di una mappa di suscettibilità delle aree in frana a scala di bacino

Le frane costituiscono uno tra i più pericolosi e dannosi eventi naturali. Negli ultimi decenni si sono succeduti numerosi eventi catastrofici che hanno provocato, oltre a danni ingenti, anche numerosi morti e dispersi. Per questo motivo cresce sempre di più l’esigenza di fornire ai pianificatori e gestori del territorio strumenti di supporto per la valutazione del pericolo da frana. In questo contesto, negli ultimi anni sono stati sviluppati nuovi approcci per la valutazione della propensione di un’area a produrre scivolamenti, basandosi sulla correlazione tra i fattori innescanti e le occorrenze di scivolamenti. Nel presente lavoro viene presentata una mappa di suscettibilità creata attra…

Modeling vegetation effects on hydrological and mechanical mechanisms of shallow landslides

Effects of vegetation in improving slope stability can be recognized on both hydrological and mechanical mechanisms. With regard to the hydrological effect, vegetation leads to lower porewater pressure and soil moisture due to interception by foliage of rainfall, which reduces the amount of water available for infiltration, or uptake by root system of soil moisture. With regard to the mechanical aspects, root system, due to their tensile strength and frictional or adhesive properties, reinforce the soil and thus increase the resistance of soil. This mechanical effect is at times the most significant and in slope stability analysis is taken into account by means of the apparent root cohesion…

Investigating the changes in extreme rainfall in Sicily

Changes in extreme rainfall are one of the most relevant sign of current climate alterations. Many studies have demonstrated an increase in rainfall intensity and a reduction of frequency in several areas of the world. This could be probably due to an acceleration of the hydrological cycle caused by temperature increase and could have, as consequence, the increase of flooding hazard. In the past, Sicily has been screened for several signals of possible climate change. Annual, seasonal and monthly rainfall data in the entire Sicilian region have been analyzed, showing a global reduction of total annual rainfall, which is mainly due to the winter reduction. Moreover, some annual maximum rainf…

Accounting for soil parameter uncertainty in a physically based and distributed approach for rainfall-triggered landslides

In this study we propose a probabilistic approach for coupled distributed hydrological-hillslope stability models that accounts for soil parameters uncertainty at basin scale. The geotechnical and soil retention curve parameters are treated as random variables across the basin and theoretical probability distributions of the Factor of Safety (FS) are estimated. The derived distributions are used to obtain the spatio-temporal dynamics of probability of failure, in terms of parameters uncertainty, conditioned to soil moisture dynamics. The framework has been implemented in the tRIBS-VEGGIE (Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator-VEGetation Generator fo…

A physically-based and distributed approach to analyze rainfall-triggered landslides at a watershed scale

Derivation of critical rainfall thresholds for landslide in Sicily

Rainfall is the primary trigger of shallow landslides that can cause fatalities, damage to properties and economic losses in many areas of the world. For this reason, determining the rainfall amount/intensity responsible for landslide occurrence is important, and may contribute to mitigate the related risk and save lives. Efforts have been made in different countries to investigate triggering conditions in order to define landslide-triggering rainfall thresholds. The rainfall thresholds are generally described by a functional relationship of power in terms of cumulated or intensity event rainfall-duration, whose parameters are estimated empirically from the analysis of historical rainfall e…

Monitoraggio di frane attivate da precipitazione a supporto di un Early Warning System: Progetto SESAMO

Analisi di storm tracking nell’area urbana di Palermo attraverso dati di pioggia ad alta risoluzione

La conoscenza della distribuzione spaziale e temporale delle piogge di breve durata, nonché la loro cinematica, sono alcuni tra i fattori più importanti che stanno alla base dell’approssimazione dei modelli di trasformazione afflussi-deflussi nei bacini urbani. L'incertezza dovuta alla variabilità spaziale della pioggia può influenzare, ad esempio, le performance dei modelli di drenaggio urbano. Un'adeguata conoscenza della variabilità spaziale e temporale delle precipitazioni può essere considerata un passo fondamentale per un'esatta interpretazione dei processi idrologici di base che avvengono nei sistemi di drenaggio urbano durante gli eventi di pioggia intensi. L'analisi di tali informa…

The SESAMO early warning system for rainfall-triggered landslides

The development of Web-based information systems coupled with advanced monitoring systems could prove to be extremely useful in landslide risk management and mitigation. A new frontier in the field of rainfall-triggered landslides (RTLs) lies in the real-time modelling of the relationship between rainfall and slope stability; this requires an intensive monitoring of some key parameters that could be achieved through the use of modern and often low-cost technologies. This work describes an integrated information system for early warning of RTLs that has been deployed and tested, in a prototypal form, for an Italian pilot site. The core of the proposed system is a wireless sensor network coll…

A spatially distributed and physically based tool to modelling rainfall-triggered landslides

Landslides are a serious threat to lives and property throughout the world. Over the last few years the need to provide consistent tools and support to decision-makers and land managers have led to significant progress in the analysis and understanding of the occurrence of landslides. The causes of landslides are varied. Multiple dynamic processes are involved in driving slope failures. One of these causes is prolonged rainfall, which affect slope stability in different ways. Water entering the ground beneath a slope always causes a rise of the piezometric surface, which in turn involves an increase of the pore-water pressure and a decrease of the soil shear resistance. For this reason, kno…

Hydrological and mechanical effects of roots in shallow landslide analysis: A physically-based approach

This study provides the first insights of a methodology for estimating the additional cohesion exercised by vegetation roots in a hillslope landslide analysis within a coupled ecohydrological-stability model. The existing coupled system is able to simulate the spatial distribution and temporal dynamics of Factor of Safety (FS) as a function of soil moisture dynamics. The model takes into account the hydrological effects of vegetation which, through the root water uptaking, contributes in reducing the soil water content and, thus, in increasing the slope stability. The additional mechanical root cohesion is estimated in a Fiber Bundle Model (FBM) framework that allows for the evaluation of t…

Strategies investigation in using artificial neural network for landslide susceptibility mapping: application to a Sicilian catchment

Susceptibility assessment of areas prone to landsliding remains one of the most useful approaches in landslide hazard analysis. The key point of such analysis is the correlation between the physical phenomenon and its triggering factors based on past observations. Many methods have been developed in the scientific literature to capture and model this correlation, usually within a geographic information system (GIS) framework. Among these, the use of neural networks, in particular the multi-layer perceptron (MLP) networks, has provided successful results. A successful application of the MLP method to a basin area requires the definition of different model strategies, such as the sample selec…

Impact of hydrologically driven hillslope erosion and landslide occurrence on soil organic carbon dynamics in tropical watersheds

The dynamics of soil organic carbon (SOC) in tropical forests play an important role in the global carbon (C) cycle. Past attempts to quantify the net C exchange with the atmosphere in regional and global budgets do not systematically account for dynamic feedbacks among linked hydrological, geomorphological, and biogeochemical processes, which control the fate of SOC. Here we quantify effects of geomorphic perturbations on SOC oxidation and accumulation in two adjacent wet tropical forest watersheds underlain by contrasting lithology (volcaniclastic rock and quartz diorite) in the Luquillo Critical Zone Observatory. This study uses the spatially-explicit and physically-based model of SOC dy…

Evaluation of fine soil moisture data from the IFloodS (NASA GPM) Ground Validation campaign using a fully-distributed ecohydrological model

Analitical deriving of the field capacity through soil bundle model

The concept of field capacity as soil hydraulic parameter is widely used in many hydrological applications. Althought its recurring usage, its definition is not univocal. Traditionally, field capacity has been related to the amount of water that remains in the soil after the excess water has drained away and the water downward movement experiences a significant decresase. Quantifying the drainage of excess of water may be vague and several definitions, often subjective, have been proposed. These definitions are based on fixed thresholds either of time, pressure, or flux to which the field capacity condition is associated. The flux­based definition identifies the field capacity as the soil m…

Relationship Between Extreme Rainfall and Surface Temperature in Sicily (Italy)

The study of the relationship between extreme rainfall events and surface temperature represents an important issue in hydrology and meteorology and it could be of capital importance for evaluating the effect of global warming on future precipitation. Various approaches have been tested across different parts of the world, and, in many cases, it has been observed an intensification of precipitation with increasing temperature consistently with the thermodynamic Clausius-Clapeyron relation (CC-rate of 6-7% °C-1), according to which a warmer atmosphere is capable of holding more moisture. Nevertheless, in different locations, the scaling rate between temperature and extreme precipitation has …

Derivation of critical rainfall thresholds for landslide

Rainfall is the primary trigger of shallow landslides that can cause fatalities and economic losses in many areas of the world. For this reason, determining the rainfall amount responsible for landslide occurrence is important, and may contribute to mitigate the related risk. In particular, the definition of critical rainfall-triggering thresholds for landslide is one of the most used approach, which is based on empirical methods. The creation of the rainfall-landslide database represents one of the main efforts in this kind of analysis, which requires a perfect agreement between the rainfall and landslide information in terms of timing. This requirement is easily obtained in the case of th…

Modeling the mechanical and hydrological controls of vegetation in shallow landslides

Rainfall Induced Landslides in Puerto Rico

Landslides are a major geologic hazard in the United States, typically triggered by rainfall, earthquakes, volcanoes and human activity. Rainfall-induced landslides are the most common type in the island of Puerto Rico, with one or two large events per year. We performed an island-wide determination of static landslide susceptibility and hazard assessment as well as dynamic modeling of rainfall-induced shallow landslides in a particular hydrologic basin. Based on statistical analysis of past landslides, we determined that reliable prediction of the susceptibility to landslides is strongly dependent on the resolution of the digital elevation model (DEM) employed and the reliability of the ra…

Effetto della distribuzione temporale della precipitazione sull’innesco di movimenti superficiali a scala di bacino

Influence of soil erosion and landslide occurrence on the CO2 exchange with the atmosphere at the Luquillo Critical Zone Observatory, Puerto Rico

Tropical rainforests play a significant role in the global carbon (C) cycle. The Luquillo Critical Zone Observatory (LCZO) in Puerto Rico is characterized by intense erosion and landslide occurrence, which have been historically influenced by human activity and land use change, and drive the redistribution and burial of soil organic C (SOC) across the landscape. Estimates of regional C budgets do not systematically account for linkages between hydrological, geomorphological, and biogeochemical processes, which control the fate of eroded SOC. We quantify the impacts of erosion and rainfall-triggered landslides on SOC oxidation and accumulation at the Mameyes and Icacos watersheds. We develop…

Effect of raster resolution and polygon-conversion algorithm on landslide susceptibility mapping

The choice of the proper resolution in landslide susceptibility mapping is a worth considering issue. If, on the one hand, a coarse spatial resolution may describe the terrain morphologic properties with low accuracy, on the other hand, at very fine resolutions, some of the DEM-derived morphometric factors may hold an excess of details. Moreover, the landslide inventory maps are represented throughout geospatial vector data structure, therefore a conversion procedure vector-to-raster is required.This work investigates the effects of raster resolution on the susceptibility mapping in conjunction with the use of different algorithms of vector-raster conversion. The Artificial Neural Network t…

Sensitivity of extreme rainfall to temperature in semi-arid Mediterranean regions

Abstract Warmer air has the potential to hold more water vapour and, therefore, to provide more water to rainfall events. Studying the relationship between rainfall and temperature represents an emerging issue in hydrology and meteorology, since it can be considered fundamental for evaluating the effects of global warming on future precipitation. Various approaches have been tested across different parts of the world, in many cases observing an intensification of extreme precipitation at higher temperatures consistent with the well-known thermodynamic Clausius-Clapeyron relation (CC-scaling rate of 6–7%°C−1). However, at different locations for hourly time-scales, the temperature-extreme ra…

Assessing the hydrological changes due to land use alterations

The increase of urbanized areas and, consequently, of the impervious surfaces in land-use distributions may have important implications on the basin hydrological response. As a direct impact, the increase of cemented areas reduces the available storage volume for water in the watershed, which in turn exacerbates the runoff generation. Additionally, drainage pathways can be altered and the travel time to the watershed outlet considerably speeded up, with impacts on the hydrograph characteristics. The complex interactions among different hydrological processes make the estimations of the hydrological changes highly non linear. The aim of this work is using an advanced physically-based and dis…

Implications of terrain resolution on modeling rainfall-triggered landslides using a TIN- based model

Abstract This study employs a distributed eco-hydrological-landslide model, the tRIBS-VEGGIE-Landslide, to evaluate the influence of terrain resolution on the hydro-geomorphological processes involved in slope stability analysis. The model implements a Triangulated Irregular Network (TIN) to describe the topography starting from a grid-DEM. Five grid-DEM resolutions of the case study basin, i.e., 10, 20, 30 and 70 m, are used to derive the corresponding TINs. The results show that using irregular meshes reduces the loss of accuracy with coarser resolutions in the derived slope distribution in comparison to slope distributions estimated from the original grid-based DEM. From a hydrological p…

Combining a data-driven approach with seasonal forecasts data to predicting reservoir water volume in the Mediterranean area.

<p>Artificial reservoirs are one of the main water supply resources in the Mediterranean areas; their management can be strongly affected by the problems of drought and water scarcity. The reservoir water level is the result of the hydrological processes occurring in the upstream catchment, which, in turn, depend on meteorological variables, such as rainfall and temperature. It follows that a reliable forecast model of the meteorological forcing, along with a reliable water balance model, could enhance the correct management of a reservoir. With regard to the rainfall/temperature forecast model, the use of forecast climate data in the mid-term may provide further support for t…

Rainfall Induced Landslides in Puerto Rico

Modellazione eco-idrologica del ruolo delle radici nell'analisi di stabilità di un versante

Potential implications of climate change and urbanization on watershed hydrology

Abstract This paper proposes a modeling framework able to analyze the alterations in watershed hydrology induced by two recurrent drivers for hydrological changes: climate change and urbanization. The procedure is based on the coupling of a stochastic weather generator with a land use change model for the generation of some hypothetical scenarios. The generated scenarios are successively used to force a physically-based and spatial distributed hydrological model to reconstruct the basin response under different conditions. Several potential climate alterations are simulated by imposing negative and positive variations in the mean annual precipitation and a simultaneous temperature increase.…

Integration of fuzzy logic and image analysis for the detection of gullies in the Calhoun Critical Zone Observatory using airborne LiDAR data

Abstract The entire Piedmont of the Southeastern United States, where the Calhoun Critical Zone Observatory (CCZO) is located, experienced one of the most severe erosive events of the last two centuries. Forested areas were cleared to cultivate cotton, tobacco, and other crops during the nineteenth and early twentieth century and these land use changes, together with intense rainfalls, initiated deep gullying. An accurate mapping of these landforms is important since, despite some gully stabilization and reforestation efforts, gullies are still major contributors of sediment to streams. Mapping gullies in the CCZO area is hindered by the presence of dense canopy, which precludes the identif…

Creazione di un database per l’applicazione di modelli empirici di analisi di dissesto idrogeologico da precipitazione nel territorio Siciliano.

La previsione di fenomeni di dissesto idrogeologico è uno strumento essenziale di supporto alle decisioni per una corretta pianificazione del territorio. Tra tali fenomeni quelli franosi possono assumere dimensioni particolarmente rilevanti. Il fattore scatenante più ricorrente nella gran parte dei casi di frane documentate e’ costituito dalle precipitazioni. La letteratura scientifica propone diverse metodologie di analisi volte a fornire strumenti di pre-allarme in vista di un evento meteorico critico o di derivazione di mappe tematiche delle aree a maggiore suscettibilità franosa. I modelli empirici per la derivazione di soglie pluviometriche critiche di innesco risultano tra i più utili…

Landslide susceptibility mapping: a comparison of logistic regression and neural networks methods in a small sicilian catchment

The use of soil water retention curve models in analyzing slope stability in differently structured soils

Abstract This study analyzes whether and at what rate the parameterization of the Soil Water Retention Curve (SWRC) affects the analysis of shallow slope stability for differently structured unsaturated soils. Advanced empirical or physically-based equations of SWRCs have been proposed in literature to describe soil systems characterized by the so-called bimodal porous domain. In unsaturated soils, SWRC affects the stability assessment in two ways. It influences the resistance properties in terms of shear strengths, which depend on the soil water suction; and it affects the hydrological process modeling (e.g. infiltration) directly influencing soil moisture patterns and indirectly influenci…

Combining a data-driven approach with seasonal forecast data to predict reservoir water volume in the Mediterranean area

Prolonged droughts and water scarcity have become more frequent in recent years, exacerbating the problem of the artificial reservoirs management in the Mediterranean area. This study proposes a methodology which combines a Nonlinear AutoRegressive network with eXogenous input (NARX) data-driven model with Seasonal Forecasts (SFs) data, with the aim to predict the water volume stored in reservoirs at a mid-term scale, as requested by the local authority. The methodology is applied to four Sicilian reservoirs that experienced water scarcity in the recent past. SFs produced at the European Centre for Medium-Range Weather Forecasting are used to force the NARX models. Also, the reservoirs are …

MODELING THE TERRAIN EVOLUTION AT BASIN SCALE: THE GEOMORPHIC COMPONENT OF TRIBS HYDROLOGICAL MODEL

Using the hierarchical modeling approach to derive spatial distribution of precipitation and temperature datasets. A case study for the area of Sicily (Italy).

The interest for spatial interpolating climatic variables available by means of point measurements, as precipitation and temperature, arises from different needs, ranging from their usage for hydrological models to the reconstruction of climatic atlas of spatially distributed data. In some areas the spatial distribution of these variables can be related to the extremely variable morphology of the area. While simple deterministic interpolation methods usually produce just the spatial distribution of the variable of interest, implicitly relying on the spatial autocorrelation and manually tuning a few parameters, more complex statistical models, are able to derive the uncertainty associated wi…

AN INTEGRATED SYSTEM FOR THE ANALYSIS OF RAINFALL-TRIGGERED LANDSLIDES

La presente ricerca mira a fornire un sistema integrato per l'analisi delle frane attivate da precipitazioni, sviluppando due diverse metodologie: un'analisi statica per l'individuazione delle zone maggiormente propense a produrre scivolamenti (susceptibility mapping) su scala spaziale regionale, ed un'analisi dinamica per la prevision del dove e quando un evento franoso potrebbe veri carsi, ad una scala spaziale di maggior dettaglio . L'analisi statica comporta lo sviluppo di modelli statistici in grado di stimare la probabilità di eventi franosi, sulla base della correlazione tra fattori predisponenti le frane e gli eventi storici. L'esito dell'analisi è la derivazione di una mappa suscet…

Coupled stability and eco-hydrological model to predict shallow landslides

Effect of DEM resolution and threshold area on the hydrologic response at catchment scale

Parameter Uncertainty in Shallow Rainfall-triggered Landslide Modeling at Basin Scale: A Probabilistic Approach

Abstract This study proposes a methodology to account for the uncertainty of hydrological and mechanical parameters in coupled distributed hydrological-stability models for shallow landslide assessment. A probabilistic approach was implemented in an existing eco-hydrological and landslide model by randomizing soil cohesion, friction angle and soil retention parameters. The model estimates the probability of failure through an assumed theoretical Factor of Safety (FS) distribution, conditioned on soil moisture content. The time-dependent and spatially distributed FS statistics are approximated by the First Order Second Moment (FOSM) method. The model was applied to the Rio Mameyes Basin, loc…

Modeling the hydrological and mechanical effect of roots in shallow landslide analysis

The additional cohesion exercised by vegetation roots (cr) provides an important contribution to the slope stability. This study proposes a methodology for estimating the cr term in a hillslope landslide analysis within a coupled ecohydrological-stability model. The coupled model simulates the spatial distribution and temporal dynamics of the Factor of Safety (FS) as a function of soil moisture dynamics, by taking into account the hydrological effects of vegetation through the root water uptaking. The additional mechanical root cohesion is estimated in a Fiber Bundle Model framework that allows for the evaluation of the root strength as a function of stress-strain relationships of populatio…

Basin-scale water resources assessment in a sicilian basin under climate change scenarios using the conceptual model TOPDM

Climate change resulting due to the greenhouse effect is expected to have great implications for hydrological cycle and for existing surface and groundwater resources systems. The effects of climate variability and climate change have to be fully considered in current water management and planning, since water availability, quality and streamflow are very sensitive to changes in temperature and precipitation regimes. International literature proposes several models, attempting to assess accurately the available water resources under stationary and changing climatic conditions at different spatial and temporal scales. In order to assess the potential impacts of climate change on surface and …

Reti Neurali per la Realizzazione di Mappe di Suscettibilità per il Rischio Frana

La valutazione della suscettibilità al dissesto rimane uno degli approcci più utilizzanti e più efficaci per l'analisi della pericolosità da frana. Come noto, la correlazione tra il fenomeno fisico ed i fattori predisponenti sulla base degli eventi accaduti in passato è il punto chiave di tale analisi. I metodi statistici, uniti con le tecnologie GIS, si sono rilevati in questi anni tra gli strumenti più idonei e più efficaci per la valutazione e la modellazione di tale correlazione. Tuttavia, questi metodi richiedono spesso ipotesi restrittive circa la distribuzione statistica dei dati che spesso non vengono rispettate. Per tale motivo si sono anche sviluppate metodologie alternative basat…

Modifications in Water Resources Availability Under Climate Changes: A Case Study in a Sicilian Basin

Climate variability due to the greenhouse effect has important implications on hydrological processes and water resources systems. Indeed, water availability, quality and streamflow are very sensitive to changes in temperature and precipitation regimes whose effects have to be fully considered in current water management and planning. International literature proposes several models, attempting to assess accurately the available water resources under stationary and changing climatic conditions at different spatial and temporal scales. In order to assess the potential impacts of climate change on surface and groundwater resources water availability in a Southern area of Italy, a conceptual h…

Predicting reservoir water volumes in the Mediterranean area by combining a data-driven approach with seasonal forecasts data

Implementing the erosion component of a physically based and distributed model (tRIBS). A first application to an experimental basin.

A coupled stability and eco-hydrological model to predict shallow landslides

Knowledge of spatio-temporal dynamics of soil water content, groundwater and infiltration processes is of considerable importance for the understanding and prediction of landslides. Rainfall and consequent water infiltration affect slope stability in various ways, mainly acting on the pore pressure distribution whose increase causes a decrease of the shearing resistance of the soil. For such reasons rainfall and transient changes in the hydrological systems are considered the most common triggers of landslides. So far, the difficulty to monitor groundwater levels or soil moisture contents in unstable terrain have made modeling of landslide a complex issue. At the present, the availability o…

Physically-based and distributed approach to analyze rainfall-triggered landslides at watershed scale

Abstract Landslides are a serious threat to life and property throughout the world. The causes of landslides are various since multiple dynamic processes are involved in driving slope failures. One of these causes is prolonged rainfall, which affects slope stability in different ways. Water infiltrating in a hillslope may cause a rise of the piezometric surface, which, in turn, involves an increase of the pore water pressure and a decrease of the soil shear resistance. For this reason, knowledge of spatio-temporal dynamics of soil water content, infiltration processes and groundwater dynamics, is of considerable importance in the understanding and prediction of landslides dynamics. In this …

Analyzing the role of soil water retention curve in slope stability for differently structured soils

 We analyzed the mechanical and hydrological effects of soil water retention curve (SWRC) models on the slope stability analyses of soils with unimodal and bimodal behavior.  We used three different SWRC models, two bimodal models (Ross&Smettem and Dexter) vs. the traditional van Genuchten model, to evaluate the Factor of Safety (FS) of a simple designed hillslope, based on the Bishop approach for unsaturated soils. Two formulations for term were also considered.  Results indicate that in cases of clayey soils, changes in FS obtained with different SWRC models especially at soil moisture values within the residual zone. In sandy soils the choice of formulations can be more important…

EHSM: UN NUOVO MODELLO CONCETTUALE PER LA SIMULAZIONE DEL DEFLUSSO GIORNALIERO

Analisi comparativa di modelli euristici e statistici spaziali nella derivazione della suscettibilità da colate rapide di fango e detrito.

La suscettibilità da frana può essere definita come la propensione di una determinata area all’innesco di movimenti di massa, in relazione alle caratteristiche intrinseche dei terreni di copertura e del substrato, delle caratteristiche morfologiche ed alla maggiore esposizione nei confronti degli agenti climatici. Nel corso degli anni sono stati sviluppati vari metodi per valutare la suscettibilità, basati su approcci sia di tipo deterministico che statistico. Tutti i metodi si basano su poche assunzioni fondamentali secondo cui la franosità è controllata da leggi meccaniche che possono essere determinate in modo empirico, statistico o deterministico. Scopo del presente lavoro è quello di v…

The impact of climate change on extreme precipitation in Sicily, Italy

Increasing precipitation extremes are one of the possible consequences of a warmer climate. These may exceed the capacity of urban drainage systems, and thus impact the urban environment. Because short-duration precipitation events are primarily responsible for flooding in urban systems, it is important to assess the response of extreme precipitation at hourly (or sub-hourly) scales to a warming climate. This study aims to evaluate the projected changes in extreme rainfall events across the region of Sicily (Italy) and, for two urban areas, to assess possible changes in Depth-Duration-Frequency (DDF) curves. We used Regional Climate Model outputs from Coordinated Regional Climate Downscalin…

Derivation of Rainfall Thresholds for Flash Flood Warning in a Sicilian Basin Using a Hydrological Model

Abstract The damages caused by flash floods are among the most onerous in terms of loss of lives and damage to properties. Derivation of rainfall threshold is one of the approaches commonly used for the development of flash flood warning systems. Specifically, rainfall threshold is the rainfall amount that, for a given basin area and duration, is enough to cause flooding and, therefore, it indicates the maximal sustainable rainfall for a basin. The aim of this paper is deriving flash flood-rainfall thresholds for a Sicilian basin (Italy) throughout a deterministic approach. The conceptual hydrological model TOPDM was used to estimate the amount of rainfall that, for given duration, hydrolog…

Utilizzo di modelli lineari generalizzati nella derivazione di mappe di suscettibilità per il rischio idrogeologico

L’analisi statistica basata sulla correlazione tra cause e occorrenze, costituisce uno degli approcci più utilizzati in letteratura scientifica per la valutazione delle aree propense a produrre dissesti idrogeologici. Tra questi, il dissesto da frana rappresenta uno tra i più pericolosi e dannosi eventi naturali che negli ultimi anni hanno particolarmente colpito tutto il territorio nazionale. Il presente lavoro si pone come obiettivo quello di valutare l’efficienza di un modello statistico multivariato per la determinazione di mappe di suscettibilità al rischio idrogeologico, basandosi sulla correlazione tra fattori innescanti e occorrenze. Tra i modelli statistici presenti in letteratura …

tRIBS-Erosion: A parsimonious physically-based model for studying catchment hydro-geomorphic response

Our goal is to develop a model capable to discern the response of a watershed to different erosion mechanisms. We propose a framework that integrates a geomorphic component into the physically-based and spatially distributed TIN-based Real-time Integrated Basin Simulator (tRIBS) model. The coupled model simulates main erosive processes of hillslopes (raindrop impact detachment, overland flow entrainment, and diffusive processes) and channel (erosion and deposition due to the action of water flow). In addition to the spatially distributed, dynamic hydrologic variables, the model computes the sediment transport discharge and changes in elevation, which feedback to hydrological dynamics throug…

Influence of spatial precipitation sampling on hydrological response at catchment scale

Retrieving precipitation data from raingauge network is a classical and common practice in hydrology and climatology. These data represent the key input in hydrological modeling to reproduce, for example, the characteristics of a flood phenomenon. The accuracy of the model results is strongly dependent on the consistency of the monitoring network in terms of spatial scale, i.e. network density and location of raingauges, and time resolution. In this context, several studies have been carried out to analyze how the rainfall sampling influences the estimation of total runoff volume. The aim of this paper is to use a physically based and distributed-parameter hydrologic model to investigate ho…

Integration of physically based distributed hydrological model with model of carbon and nitrogen cycle: Luquillo Critical Zone Observatory, Puerto Rico

The dynamics of carbon and nitrogen cycles, increasingly influenced by human activities, are the key to the functioning of ecosystems. These cycles are influenced by the composition of the substrate, availability of nitrogen, the population of microorganisms, and by environmental factors. Therefore, land management and use, climate change, and nitrogen deposition patterns influence the dynamics of these macronutrients at the landscape scale. In this work a physically based distributed hydrological model, the tRIBS model, is coupled with a process-based multi-compartment model of the biogeochemical cycle to simulate the dynamics of carbon and nitrogen (CN) in the Mameyes River basin, Puerto …

Accounting for soil parameter uncertainty in a physically based and distributed approach for rainfall-triggered landslides

In this study we propose a probabilistic approach for coupled distributed hydrological-hillslope stability models that accounts for soil parameters uncertainty at basin scale. The geotechnical and soil retention curve parameters are treated as random variables across the basin and theoretical probability distributions of the Factor of Safety (FS) are estimated. The derived distributions are used to obtain the spatio-temporal dynamics of probability of failure, in terms of parameters uncertainty, conditioned to soil moisture dynamics. The framework has been implemented in the tRIBS-VEGGIE (Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator-VEGetation Generator fo…

Rainfall statistics changes in Sicily

Abstract. Changes in rainfall characteristics are one of the most relevant signs of current climate alterations. Many studies have demonstrated an increase in rainfall intensity and a reduction of frequency in several areas of the world, including Mediterranean areas. Rainfall characteristics may be crucial for vegetation patterns formation and evolution in Mediterranean ecosystems, with important implications, for example, in vegetation water stress or coexistence and competition dynamics. At the same time, characteristics of extreme rainfall events are fundamental for the estimation of flood peaks and quantiles which can be used in many hydrological applications, such as design of the mos…

The role of urban growth, climate change, and their interplay in altering runoff extremes

Changes in climate and urban growth are the most influential factors affecting hydrological characteristics in urban and extra-urban contexts. The assessment of the impacts of these changes on the extreme rainfall–runoff events may have important implications on urban and extra-urban management policies against severe events, such as floods, and on the design of hydraulic infrastructures. Understanding the effects of the interaction between climate change and urban growth on the generation of runoff extremes is the main aim of this paper. We carried out a synthetic experiment on a river catchment of 64 km2to generate hourly runoff time series under different hypothetical scenarios. We impos…

Effetti di urbanizzazione e cambiamenti climatici sui deflussi a scala di bacino

Fra le pressioni di natura antropica agenti sui bacini idrografici, particolare rilevanza hanno sia la progressiva perdita di suoli naturali in favore di suoli poco, o per nulla, permeabili (es. strade, edifici, parcheggi, etc.) che la regimazione e regolazione dei deflussi sulla rete di drenaggio naturale mediante interventi idraulici. In particolare, l’ultima relazione sullo stato dell’ambiente europeo a cura dell’Agenzia Europea dell’Ambiente (AEA, 2010) considera l’impermeabilizzazione dei bacini naturali come uno dei maggiori processi di degrado del suolo. L’aumento del grado di urbanizzazione dei bacini naturali, inteso come aumento della frazione impermeabile del suolo derivante dell…

Modeling the hydrological and mechanical effect of roots on shallow landslides

This study proposes a new methodology for estimating the additional shear strength (or cohesion) exerted by vegetation roots on slope stability analysis within a coupled hydrological-stability model. The mechanical root cohesion is estimated within a Fiber Bundle Model framework that allows for the evaluation of the root strength as a function of stress-strain relationships of populations of fibers. The use of such model requires the knowledge of the root architecture. A branching topology model based on Leonardo's rule is developed, providing an estimation of the amount of roots and the distribution of diameters with depth. The proposed methodology has been implemented into an existing dis…

EFFECTS OF DATA GAP ON THE CAPABILITY TO DETECT TREND IN HYDROCLIMATOLOGICAL TIME SERIES

In the last decades the growing concerns about the existence of global climatic changes push many researchers to use different trend test in order to identify whether monotonic trends exist in hydroclimatological time series such as temperature, precipitation, and streamflow. Unfortunately, these time series often suffer from missing data values mainly due to malfunctioning of gauge for specific time periods. Starting from this premise, the main target of our work is to investigate the effect of data gap in a time series on the results provided by the most used trend test: the nonparametric Mann–Kendall statistical test. Firstly, different synthetic time series characterized by different si…

Physically based modeling of rainfall-triggered landslides: a case study in the Luquillo forest, Puerto Rico

This paper presents the development of a rainfall-triggered landslide module within an existing physically based spatially distributed ecohydrologic model. The model, tRIBS-VEGGIE (Triangulated Irregular Networks-based Real-time Integrated Basin Simulator and Vegetation Generator for Interactive Evolution), is capable of a sophisticated description of many hydrological processes; in particular, the soil moisture dynamics are resolved at a temporal and spatial resolution required to examine the triggering mechanisms of rainfall-induced landslides. The validity of the tRIBS-VEGGIE model to a tropical environment is shown with an evaluation of its performance against direct observations made w…

An integrated information system for the acquisition, management and sharing of environmental data aimed to decision making

This paper reports the first results of the Project SESAMO - SistEma informativo integrato per l’acquisizione, geStione e condivisione di dati AMbientali per il supportO alle decisioni (Integrated Information System for the acquisition, management and sharing of environmental data aimed to decision making). The main aim of the project is to design and develop an integrated environmental information platform able to provide monitoring services for decision support, integrating data from different environmental monitoring systems (including WSN). This ICT platform, based on a service-oriented architecture (SOA), will be developed to coordinate a wide variety of data acquisition systems, based…

A physically-based and distributed tool for modeling the hydrological and mechanical processes of shallow landslides

This work presents the capabilities of a model, i.e. the tRIBS-VEGGIE-Landslide, in two different versions, i.e. developed within a probabilistic framework and coupled with a root cohesion module. The probabilistic model treats geotechnical and soil retention curve parameters as random variables across the basin and estimates theoretical probability distributions of slope stability and the associated “factor of safety” commonly used to describe the occurrence of shallow landslides. The derived distributions are used to obtain the spatiotemporal dynamics of probability of failure, conditioned on soil moisture dynamics at each watershed location. The framework has been tested in the Luquillo …

INFLUENCE OF RAINFALL OBSERVATION NETWORK ON MODELED HYDROLOGICAL RESPONSE

Precipitation data, one of the most important input required in hydrological modeling and forecasting, are usually recorded using raingauges which are classical and fundamental tools able to provide an estimate of rainfall at a point. The consistency of precipitation monitoring network in terms of spatial scale (network density and location of raingauges) and time resolution has to be capable to reproduce, with acceptable accuracy, the characteristics of the flood phenomenon. In this context, over the last thirty years, several studies concerning the influence of point measurement of rainfall for the estimation of total runoff volume have been carried out. Aim of this paper is using a physi…

Effects of Digital Elevation Model resolution on evaluation of landslide susceptibility with a logistic regression model.

The use of statistical methods together with the GIS technologies is currently one of the most efficient tools in the assessment of landslide susceptibility. The correlation between the physical phenomenon and its triggering factors depends on several factors, including the resolution at which the elevation data are represented in a Digital Elevation Model (DEM). The resolution becomes increasingly important as the use of DEM data is extended for spatial prediction of terrain attributes such as slope, aspect, plan and profile curvature, etc., which are considered as triggering factors of the landslides. Many methods exist in scientific literature to capture and model the correlation between…