Probabilistic Flood Hazard Mapping Using Bivariate Analysis Based on Copulas

This study presents a methodology to extract probabilistic flood hazard maps in an area subject to flood risk, taking into account uncertainties in the definition of design hydrographs. Particularly, the authors present a new method to produce probabilistic inundation and flood hazard maps in which the hydrological input (i.e., synthetic flood design event) to a 2D hydraulic model has been obtained by using a bivariate statistical analysis (copulas) to generate flood peak discharges and volumes. This study also aims to quantify the contribution of boundary conditions’ uncertainty in order to evaluate the effect of this uncertainty source on probabilistic flood hazard mapping. Different comb…

Statistica degli estremi idrologici in Sicilia

Il carattere torrentizio di tutti i più importanti corsi d'acqua siciliani ha da sempre determinato esondazioni delle onde di piena e conseguenti allagamenti delle aree limitrofe provocando danni rilevanti. La valutazione delle piene e del rischio idrologico ad esse connesso può essere condotta secondo un approccio di tipo probabilistico attraverso il quale si determini una relazione tra la portata di piena di assegnata frequenza probabile ed il tempo di ritorno. In questo articolo sono richiamate le leggi di distribuzione di probabilità solitamente usate in idrologia, con particolare riferimento all'analisi probabilistica del valore massimo annuale della portata al colmo di piena e dell'al…

Influenza della misura di verosomiglianza nello studio di incertezza nella modellazione afflussi deflussi di un bacino mediterraneo

Probabilistic characterization of flood hazard using bivariate analysis based on copulas

This study presents an innovative approach to obtain flood hazard maps where hydrological input (synthetic flood design event) to a 2D hydraulic model has been defined by generating flood peak discharges and volumes from a bivariate statistical analysis, through the use of copulas. Synthetic hydrographs were generated by means two different approaches: an indirect one, where rainfall were generated by a stochastic bivariate rainfall generator to be entered a distributed conceptual rainfall-runoff model that consisted of a soil moisture routine and a flow routing routine; and a direct one, where stochastic generation of flood peaks and flow volumes have been obtained via copulas, which descr…

Efficienza idrologico-idraulica di pavimentazioni semi-permeabili per il controllo degli allagamenti pluviali

La sostenibilità del binomio “acqua – città” è uno spunto interessante di discussione e confronto nell’ambito delle diverse discipline che affrontano il tema dell’ambiente urbano, delle sue continue trasformazioni, e della necessità di resilienza agli allagamenti. Le soluzioni tecniche e tecnologiche oggi a disposizione di chi si occupa di queste problematiche, per affrontare il tema di un rapporto sostenibile tra l’acqua e l’ambiente urbano sono molteplici, alcune tradizionali e di consolidata esperienza, altre innovative e di più recente applicazione sul campo. L’urbanizzazione influisce negativamente sulla formazione e propagazione dei deflussi; nelle aree urbanizzate i rapidi processi d…

Valutazione dell'inquinamento proveniente da fonti concentrate e diffuse in un bacino mediterraneo

Changes in the hydrological response of two sicilian basins affected by fires

Point and no point pollution assessment for a receiving water body quality management

Stima dell'erosione idrica in due bacini siciliani mediante tecniche GIS

On the influence of using binary and distributed information for 2D hydraulic model calibration and uncertainty evaluation

Floods are considered the most frequent natural disaster world-wide and may have serious socio economic impacts in a community. In order to accomplish flood risk mitigation, flood risk analysis and assessment are required to provide information on current or future flood hazard and risks. Hazard and risk maps involve different data, expertise and effort, depending also on the end-users. More or less advanced deterministic approaches can be used, but intuitively probabilistic approaches seem to be more correct and suited for modelling flood inundation given typical uncertainties. Two very important matters remain open for research: the calibration of hydraulic models (oriented towards the es…

On the use of innovative post-event data for reducing uncertainty in calibrating flood propagation models

Hydraulic models for flood propagation description are an essential tool in many fields and are used, for example, for flood hazard and risk assessments, evaluation of flood control measures, etc. However, the calibration of these models is still underdeveloped in contrast to other models like e.g. hydrological models essentially for lacking of specific data, because extreme flood events occur rarely and very rarely are monitored. Very often calibration data, when available, consist of water depths measure in some scattered points. For an inundation event occurred on November 2011 in Sicily, new sources of data were available due to the availability of many videos recorded by ‘common’ peopl…

Influence of rating curve uncertainty on daily rainfall–runoff model predictions

River discharge observations are usually affected by uncertainty, which is due to many concurrent causes and strongly affects the response of rainfall-runoff models. The present paper is aimed at studying the influence of imperfect rating curve knowledge on the uncertainty of the response of a daily conceptual linear-nonlinear rainfall-runoff model. To describe the impact of imperfect rating curve knowledge, simulations have been conducted using a conceptual rainfall-runoff model and continuous daily series of rainfall, air temperature and discharges recorded in a Sicilian catchment. The GLUE procedure was used to introduce the uncertainty of the rating curve in a classical rainfall-runoff …

Affidabilita’ e analisi di incertezza nelle scale di deflusso di corsi d’acqua con caratteristiche di forte variabilità

Modelling hydrology and water quality in a Mediterranean catchment

In this study the SWAT model has been used in order to analyse and quantify pollution dynamics at basin scale depending on concentrated and diffuse sources. Nowadays, the receiving water bodies quality safeguarding is of growing importance due to the promulgation of recent laws as well as the growing sensitivity regarding the environment issues by the scientific and practitioner committee. Recently the EU 2000/60 (Water Framework Directive) makes the analysis of receiving water bodies even more complex by integrating the pollution in urban areas in a framework of the pollution sources at catchment scale. and making necessary further integration of environmental impacts associated with disch…

Analisi di incertezza nella risposta quali-quantitativa a scala giornaliera di un bacino naturale

Effects of forest fires on flood frequency curves in a Mediterranean catchment

The effect of land-use change on the flood frequency curve (FFC) in a natural catchment is analysed. To achieve this, a simple methodology for the derivation of FFCs in land-use change scenarios is proposed. The adopted methodology, using a stochastic model in Monte Carlo simulation of FFCs, was found to provide a useful framework for detecting changes in flood magnitudes in both pre- and post-fire conditions. In particular, the importance of the antecedent soil moisture condition in the determination of the flood frequency distribution was analysed. The analysis of FFCs for pre- and post-fire conditions shows an increase in the average value of Curve Number and a decrease in the catchment …

Valutazione dell'inquinamento diffuso in corsi d'acqua a carattere torrentizio

Equifinality and uncertainty of the quali-quantitative response of a natural catchment

Multiregression Analysis of the Kinetic Constants in Ephemeral Rivers: The Case Study of the Oreto River

Profuse efforts have been committed to develop efficient tools to measure the ecological status of the receiving water body quality state. The recurrence to mathematical models as support tools for the receiving water body quality assessment can be an optimal choice. Indeed, mathematical models can allow to build-up the cause effect relationship between polluting sources and receiving water quality. Regarding the river water quality modelling, two different kinds of river can be single out: large and small rivers. In the modelling approach, the main differences between the two types of river are reflected in the model kinetic constants. Indeed, the main quality processes which control and g…

Quantification of diffuse and concentrated pollutant loads at the watershed-scale: an Italian case study

In this study, diffuse and point source pollutant loads were evaluated using an Italian case study: the Nocella catchment, which has been subject to extensive monitoring. The Nocella catchment is located in Sicily (Italy) and has an area of about 60 km2. The river receives wastewater and stormwater from two urban areas drained by combined sewers. The two sewer systems, two wastewater treatment plants and a river reach were monitored during both dry and wet weather periods. Thereafter, an integrated catchment-scale model was applied to simulate point pollutant sources, i.e., pollution coming from the urban drainage system, and nonpoint pollutant sources, i.e., pollution coming from agricultu…

Hydroclimatological characterisation of extreme events in Sicilian region finalised to describe regional hydrological patterns and to predict flood regime in ungauged catchments.

Receiving water body quality assessment: an integrated mathematical approach applied to an Italian case study

This study presents a basin-scale approach to the analysis of receiving water body quality considering both point and non-point pollution sources. In particular, this paper describes an extensive data gathering campaign carried out in the Nocella catchment, which is an agricultural and semi-urbanised basin located in Sicily, Italy. Two sewer systems, two wastewater treatment plants and a river reach were monitored during both dry and wet weather periods. A mathematical model of the entire integrated system was also created. Specifically, a detailed modelling approach was developed by employing three well known models: Storm Water Management Model, GPS-X and Soil and Water Assessment Tool. T…

Rainfall thresholds derivation for warning pluvial flooding risk in urbanised areas

Aim of this work is the development of an operational tool for pluvial flooding warning in an urban area based on off-line rainfall thresholds derived by coupling a rainfall–runoff modelling and a hydraulic routing. The critical conditions considered for issue flood warnings were not only based on the water stage, but also on the extension of the flooded area. Further, a risk assessment framework for quantifying the reliability of the rainfall thresholds has been included; rainfall thresholds used in pluvial flooding warning should be influenced by the uncertainties in the rainfall characteristics (i.e. rainfall duration, depth and storm pattern). This risk assessment framework incorporates…

Estimation of flood inundation probabilities using hydrodynamic indexes with uncertainty analysis

Applicability of hydrological similarities measures based on linkage between rain and flood regime for regional flood frequency analysis in Mediterranean catchment.

Mappatura probabilistica della pericolosità idraulica: analisi dell’incertezza legata all’utilizzo di un approccio bivariato per l’analisi di frequenza delle portate di piena

Estimation of synthetic flood design hydrographs using a distributed rainfall–runoff model coupled with a copula-based single storm rainfall generator

Abstract. In this paper a procedure to derive synthetic flood design hydrographs (SFDH) using a bivariate representation of rainfall forcing (rainfall duration and intensity) via copulas, which describes and models the correlation between two variables independently of the marginal laws involved, coupled with a distributed rainfall–runoff model, is presented. Rainfall–runoff modelling (R–R modelling) for estimating the hydrological response at the outlet of a catchment was performed by using a conceptual fully distributed procedure based on the Soil Conservation Service – Curve Number method as an excess rainfall model and on a distributed unit hydrograph with climatic dependencies for the …

Derivation of flood frequency curves in poorly gauged Mediterranean catchments using a simple stochastic hydrological rainfall-runoff model

In this paper a Monte Carlo procedure for deriving frequency distributions of peak flows using a semi-distributed stochastic rainfall-runoff model is presented. The rainfall-runoff model here used is very simple one, with a limited number of parameters and practically does not require any calibration, resulting in a robust tool for those catchments which are partially or poorly gauged. The procedure is based on three modules: a stochastic rainfall generator module, a hydrologic loss module and a flood routing module. In the rainfall generator module the rainfall storm, i.e. the maximum rainfall depth for a fixed duration, is assumed to follow the two components extreme value (TCEV) distribu…

Analysis of the linkage between hydrological and climatic information finalised to descrive flood regime in Sicily.

Applicazione del modello SWAT a un bacino siciliano fortemente antropizzato.

Flood proofing measures cost-efficiency analysis for hydraulic risk mitigation in an urbanized riverine area.

<div> <div> <div> <p><strong>Flood proofing measures cost-efficiency analysis for hydraulic risk mitigation in an urbanized riverine area</strong></p> <p>Ugo Ventimiglia <sup>2</sup>, Angela Candela <sup>1,</sup> Giuseppe Tito Aronica <sup>2</sup></p> <p><sup>1 </sup>Department of Engineering, University of Palermo, Palermo, Italy</p> <p><sup>2 </sup>Department of Engineerin…

DEFINIZIONE DI IDROGRAMMI SINTETICI PER LA REDAZIONE DI MAPPE DI PERICOLOSITA’ D’INONDAZIONE

Obiettivo di questo studio è la definizione di idrogrammi sintetici da utilizzarsi come input per la redazione di mappe di pericolosità d’inondazione; in particolare nel lavoro sono state messe a confronto tre diverse metodologie entrambe basate su tecniche di tipo stocastico. La prima prevede il calcolo degli idrogrammi di piena attraverso una procedura di tipo Monte Carlo generando tre elementi che caratterizzano gli idrogrammi: portata al colmo, volume di piena e forma dell’onda. La seconda riguarda la generazione di idrogrammi sintetici a partire dalla derivazione della curva di riduzione dei colmi di piena basata su forma inferenziale. Le procedure adottate non portano agli stessi risu…

Influence of surface roughness in hydrological response of semiarid catchments

Abstract Here, an investigation has been carried out in order to understand the influence of the surface roughness in the definition of the hydrological response of semiarid catchments. Following a previous study of one of the authors, a modified version of TOPMODEL is used, in which the convolution routing procedure has been extended to the hillslopes by specifying the routing velocity for each pixel of the watershed. These velocities have been linked to the watershed land use through the different surface roughness whose coefficients has been derived on the basis of Engman's table. In this paper, roughness coefficient distributions are expressed as function of a unique value treated as a …

VALUTAZIONE DEI CARICHI INQUINANTI DI ORIGINE DIFFUSA E CONCENTRATA A SCALA DI BACINO: APPLICAZIONE A UN CASO DI STUDIO SICILIANO

Obiettivo della ricerca è stata la predisposizione di un modello di tipo integrato a scala di bacino al fine di ricostruire la dinamica dei carichi inquinanti concentrati di origine civile e produttiva e dei carichi diffusi di origine agricola e zootecnica, in osservanza dei nuovi criteri di gestione dei corpi idrici superficiali introdotti dalle normative nazionale ed europea (Direttiva UE 2000/60, D.lgs. 152/2006). Il modello messo a punto è stato applicato al bacino del fiume Nocella, ubicato in Sicilia e ritenuto un idoneo banco di prova in quanto recapito di numerosi scarichi in forma concentrata e diffusa. I primi derivano in modo continuo dagli impianti di depurazione a servizio di d…

Propagation of precipitation measurement biases into the hydraulic modelling of urban drainage systems: a case study

Precipitation is the primary source of freshwater, while it can have great socio-economical impacts associated with extreme weather events such as floods and droughts. Good quality hydro-meteorological data is an essential condition not only for climate analysis but also for warning systems, hydraulic structures design, risk assessment, etc. In fact, precipitation is one of the most intensively used variables in hydrological modelling and its measurement accuracy is of foremost importance (Peterson et al., 1998). Accurate and timely knowledge of precipitation characteristics at urban and natural basins scales is essential for understanding how different catchment hydrological systems operat…

Probabilistic floodplain hazard mapping: managing uncertainty by using a bivariate approach for flood frequency analysis

Floods are a global problem and are considered the most frequent natural disaster world-wide. Many studies show that the severity and frequency of floods have increased in recent years and underline the difficulty to separate the effects of natural climatic changes and human influences as land management practices, urbanization etc. Flood risk analysis and assessment is required to provide information on current or future flood hazard and risks in order to accomplish flood risk mitigation, to propose, evaluate and select measures to reduce it. Both components of risk can be mapped individually and are affected by multiple uncertainties as well as the joint estimate of flood risk. Major sour…

Attività di monitoraggio di corpi idrici fluviali per l’individuazione dello stato di qualità: applicazione al bacino del fiume Oreto

Analisi stocastica delle condizioni di efficienza del drenaggio superficiale nella gestione del rischio di allagamento nelle aree urbane

Gli allagamenti in aree urbane si verificano con una certa frequenza anche in seguito ad eventi di precipitazione meno severi (intensi) dell’evento di progetto con cui sono state dimensionate le reti di fognatura. Le caditoie sono, in questi casi, i nodi critici: l’efficienza del drenaggio superficiale è assicurata solo quando la loro progettazione, posizionamento e manutenzione è effettuata a regola d’arte. Assumendo il corretto dimensionamento, posizionamento e manutenzione periodica delle caditoie, l’ulteriore fonte di incertezza sul grado di funzionamento delle stesse, risiede in imprevedibili effetti di ostruzioni dovute ad esempio alla presenza di macchine, o di altro materiale non ri…

Investigating reservoir sediment and watershed erosion using the WEPP model

Uncertainty in Quali-Quantitative Response of a Natural Catchment on a Daily Basis

LA MODELLAZIONE DEI CORSI D’ACQUA A CARATTERE TORRENTIZIO: IL CASO DI STUDIO DEL FIUME ORETO

I modelli di qualità fluviale possono essere dei validi strumenti per la valutazione e la gestione della qualità dei corpi idrici ricettori. Tuttavia tali modelli richiedono una calibrazione accurata al fine di valutare i parametri che in essi compaiono; ciò richiede una vasta banca dati di qualità, raramente disponibile nel caso di piccoli corsi d’acqua fluviali a carattere torrentizio, per il limitato interesse spesso prestato a tali tipologie di corpi idrici. Nella memoria viene presentato un modello semplificato di qualità fluviale; il modello trae spunto dal classico modello di Streeter e Phelps, integrato al fine di tener conto dei principali processi fisici, chimici e biologici per l…

Estimation of flood inundation probabilities using global hazard indexes based on hydrodynamic variables

In this paper a new procedure to derive flood hazard maps incorporating uncertainty concepts is presented. The layout of the procedure can be resumed as follows: (1) stochastic input of flood hydrograph modelled through a direct Monte-Carlo simulation based on flood recorded data. Generation of flood peaks and flow volumes has been obtained via copulas, which describe and model the correlation between these two variables independently of the marginal laws involved. The shape of hydrograph has been generated on the basis of a historical significant flood events, via cluster analysis; (2) modelling of flood propagation using a hyperbolic finite element model based on the DSV equations; (3) de…

A cost efficiency analysis of flood proofing measures for hydraulic risk mitigation in an Urbanized riverine area

Non-structural measures for flood risk mitigation are often more economically accessible, easier to implement, and are highly effective, especially in view of the pursuit of risk resilience objectives. Among the non-structural measures, more importance is increasingly being attributed to flood proofing interventions. There are two main types of flood proofing: dry proofing and wet proofing. An example of dry proofing is shielding, which involves the use of flood barriers that can be installed in the entrances of buildings or outside the buildings in order to avoid contact with the houses and deviate the water flow. Their use must be supported by a detailed hydraulic analysis to ensure the c…

Monitoring activity to assess the quality conditions of a river: the case study of Oreto, Italy

Derivation of rainfall thresholds for pluvial flood risk warning in urbanised areas

In the recent past throughout the Mediterranean area, many extreme events such as floods, debris flows and landslides occurred. Mediterranean ephemeral streams have specific features compared to other river systems; their basins are small and highly torrential and may generate flash-floods (Camarasa-Belmonte & Soriano-Garcia, 2012). Moreover, the rapid transformation processes of urban areas induced the increase of catchment imperviousness and the derived increase of surface runoff generated during rainfall events. However, flooding events in urban areas occur quite frequently as a consequence of rain events of lower intensity than the design one, even in case of correct network dimensionin…

Estimation of flood design hydrographs using bivariate analysis (copula) and distributed hydrological modelling

Abstract. In this paper a procedure to derive Flood Design Hydrographs (FDH) using a bivariate representation of rainfall forcing (rainfall duration and intensity) using copulas, which describe and model the correlation between these two variables independently of the marginal laws involved, coupled with a distributed rainfall-runoff model is presented. Rainfall-runoff modelling for estimating the hydrological response at the outlet of a watershed used a conceptual fully distributed procedure based on the soil conservation service – curve number method as excess rainfall model and a distributed unit hydrograph with climatic dependencies for the flow routing. Travel time computation, based o…

DERIVAZIONE DI IDROGRAMMI DI PIENA ATTRAVERSO L’ACCOPPIAMENTO DI MODELLI STOCASTICI BIVARIATI DELLE PRECIPITAZIONI E E MODELLI AFFLUSSI - DEFLUSSI DISTRIBUTI

In questo studio viene presentata una procedura di tipo Monte Carlo per la derivazione delle curve di frequenza delle portate al colmo e dei volumi corrispondenti basata sull’accoppiamento di un modello di generazione delle forzanti pluviometriche tramite copule e un modello di trasformazione afflussideflussi di tipo distribuito. Tale procedura è stata applicata ad un caso di studio siciliano; i risultati ottenuti hanno mostrato la bontà del modello a riprodurre le statistiche complesse delle grandezze idrologiche a fronte di un basso numero di parametri modellistici e di un ridotto sforzo computazionale.

Pluvial flooding in urban areas: the role of surface drainage efficiency

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…

Nutrient sources in a Mediterranean catchment and their improvement for water quality management

Changes in land-use or management strategies may affect water outflow, sediment and nutrients loads. Thus, there is an increasing demand for quantitative information at the catchment scale that would help decision makers or planners to take appropriate decisions. The characterisation of water status, the description of pollution sources impact, the establishment of monitoring programs and the implementation of river basin management plans require an analysis of the current basin status and estimates of the relative significance of the different sources of pollution. Particularly, in this study the Soil and Water Assessment Tool (SWAT2000) model was considered since it is an integrated hydro…

Hydrological simulation using a bivariate approach based on copulas for the assessment of inundation risk scenarios down-stream of flood control reservoirs

Aim of this study was to assess operational reservoir rules for evaluating flood risk scenarios using a MonteCarlo bivariate framework. It involves a stochastic procedure to calculate flood hydrographs and, then, flood inundation area evaluation through a 2D hydraulic model to estimate the inundation risk and, as consequence, the relative damage evaluation, under different operation strategies of an upstream reservoir. The entire procedure can be summarised as follows: single synthetic stochastic rainfall events have been derived using a Monte Carlo proce-dure through a bivariate copulas analysis; synthetic bivariate stochastic inflow hydrographs have been derived by using a conceptual full…

A Regional Methodology for Deriving Flood Frequency Curves (FFC) in Partially Gauged Catchments with Uncertain Knowledge of Soil Moisture Conditions

Analysis of the Effects of Reservoir Operating Scenarios on Downstream Flood Damage Risk Using an Integrated Monte Carlo Modelling Approach

The aim of this study is to analyse the effects of reservoir operating scenarios, for flood damage evaluation downstream of a dam, using a Monte Carlo bivariate modelling chain. The proposed methodology involves a stochastic procedure to calculate flood hydrographs and the evaluation of the consequent flood inundation area by applying a 2D hydraulic model. These results are used to estimate the inundation risk and, as consequence, the relative damage evaluation under different water level conditions in an upstream reservoir. The modelling chain can be summarized as follows: single synthetic stochastic rainfall event generation by using a Monte Carlo procedure through a bivariate copulas ana…

Un nuovo approccio per la determinazione del deflusso minimo vitale nei corsi d’acqua a carattere torrentizio.

INVESTIGATING RESERVOIR SEDIMENT AND CATCHMENT EROSION USING THE WEPP MODEL

EVALUATION OF DIFFUSE AND CONCENTRATED POLLUTION AT WATERSHED SCALE

The study presents an integrated approach in order to analyse and quantify pollution dynamics at basin scale depending on concentrated and diffuse sources. More specifically, an integrated model for urban drainage system has been exploited in order to simulate the complex sewer network - wastewater treatment plant and receiving water body. Moreover, a quali-quantitative model has been developped in order to simulate the non-point sources pollutant (agricultural and zoo-technical) in term of water river discharges and nutrient, produced from the wash off of soils. Finally, different models have been coupled in order to reconstruct the whole pollutant load for the receiving water body and to …

How different likelihood measures play a role in studying the uncertainty in the rainfall-runoff modelling of a mediterranean catchment