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…

Uncertain Characterization of Flood Hazard Using Bivariate Analysis Based on Copulas

This study presents a methodology to derive probabilistic flood hazard map in flood prone areas taking into account uncertainties in the definition of design-hydrographs. Particularly, we present an innovative approach to obtain probabilistic inundation and 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. This study also aims to quantify the contribution of boundary conditions uncertainty in order to explore the impact of this uncertainty on probabilistic flood hazard mapping. The uncertainty of extreme flood eve…

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

Specific calibration and predictive uncertainty evaluation strategies for flood propagation models

Hydraulic models are an essential tool in many fields, e.g. civil engineering, flood hazard and risk assessments, evaluation of flood control measures, etc. Nowadays there are many models of different complexity regarding the mathematical foundation and spatial dimensions available, and most of them are comparatively easy to operate due to sophisticated tools for model setup and control. However, the calibration of these models is still underdeveloped in contrast to other models like e.g. hydrological models or models used in ecosystem analysis. This has basically two reasons: First, the lack of relevant data against the models can be calibrated, because flood events are very rarely monitor…

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…

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…

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…

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…