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Autre Publication Scientifique Année : 2009

Value of distributed post-flood maximum discharge estimation for the evaluation of a regional flash-flood modelling approach

Résumé

In September 2002 a flash flood killed 23 human lives and generated 1.2 billion Euros of damages in less than 24 hours over an area of 20 000 km2 located in the south of France. The Gard river basin was hit by a storm that locally received more than 600 mm in one day. This storm triggered catastrophic flash floods on many upstream tributaries as well as the most important flood ever reported of the major rivers (Gard, Ceze and Vidourle). The distributed prediction of such extreme events remains an open question due to scarcity of observations and the unknown individual hydrological behaviour of very small basins. Due to the high spatial and temporal variability of rainfall and of the physiographic conditions, physically-based distributed hydrological models offer perspective for the simulation of such flash-floods at a regional scale, and more specifically in small ungauged basins which are recognized as the most vulnerable. However, the evaluation of model performance for such events remains largely open. Traditional stream gauge networks provide estimate at only a few locations, and these values are very uncertain for large discharges. Indeed, stage discharge relationship are in general extrapolated far beyond gauged values -if they are not destroyed- for extreme floods. Alternative sources of data are therefore necessary for model evaluation. In this paper, such an alternative solution is presented and illustrated using data from the Gard September 2002 event. It consists in using a post flood field survey data set made of estimation of maximum peak discharge and time of peak. Such estimations are conducted at the regional scales for catchments of various sizes (for a few to about 100 km2) in areas affected by different rainfall amounts in order to sample a large range of hydrological responses. These estimations are derived from hydrological investigation using interviews of witnesses and river cross-sections surveys.
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Dates et versions

hal-00457576 , version 1 (17-02-2010)

Identifiants

  • HAL Id : hal-00457576 , version 1

Citer

Isabelle Braud, C. Manus, S. Anquetin, P. Viallet, Jd Creutin, et al.. Value of distributed post-flood maximum discharge estimation for the evaluation of a regional flash-flood modelling approach. 2009, 1p. ⟨hal-00457576⟩
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