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Forecasting Flash Floods with an Operational Model

Application in the South-East of France (Gard)
  • P.A. Ayral
  • S. Sauvagnargues-Lesage
  • S. Gay
  • F. Bressand
Part of the Advances in Natural and Technological Hazards Research book series (NTHR, volume 25)

Abstract

The flash flood forecasting model ALHTAÏR (“Alarme Hydrologique Territoriale Automatisée par Indicateur de Risque”) has been developed during the last five years by the flood-warning service of the Gard Region (SAC-30), in the South-East of France. A spatial version for the flash flood forecasting model is described in this paper. This flash flood forecasting model is divided in three separate tools, which allow a flood hydrograph simulation for each location, covering all the rivers of the Gard Region, in a real time processing: CALAMAR® simulates the rainfall intensity on each square kilometre of the study area every five minutes. This georeferenced information is obtained by the interpretation of radar images. HYDROKIT® gives the hydrographical characteristics of a studied watershed using a DEM (Digital Elevation Model) for calculating the concentration time. ALHTAÏR software, processes the data obtained by the two previous tools and with a module of time concentration and a module of production (calculation of effective rainfall) calculating in real time the flood hydrograph. The model that calculates the effective rainfall, based on the Horton principle, takes six parameters into account. For the first version of ALHTAÏR, these parameters are the same for the whole SAC-30 supervised territory. The principal results of this version show a good flood crest synchronization but a general overestimation of the peak flow. This result was observed during the flash floods of the Gard Region in September 2002. To improve the ALTHAÏR results, a spatial approach has been tested. The results presented in the paper, show that the spatial approach according to infiltration capacity improves the reconstitution of the flood hydrograph

Keywords

flash flood forecasting model flood warning service Mediterranean region 

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References

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Copyright information

© Springer 2007

Authors and Affiliations

  • P.A. Ayral
    • 1
  • S. Sauvagnargues-Lesage
    • 1
  • S. Gay
    • 1
  • F. Bressand
    • 2
  1. 1.Ecole des Mines d‘AlèsF-30319France
  2. 2.DDE-SAC-30F-30907 NîmesFrance

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