The 8-9 September 2002 rain event in the Gard region, France: Rainfall estimation using radar and rain gauge observations

This study aims at evaluating various rainfall estimation techniques to be used in the context of hydrological post-event investigations. The rich radar and rain gauge datasets collected during the 8-9 september 2002 catastrophic rain event are considered for this purpose. Spatially variable radar calibration techniques based on the << hydrologic visibility >> concept and on raingauge-radar correction factors calculated at the event time scale are shown to significantly improve the consistency of the radar estimates with respect to independent rain gauge measurements at the hourly timescale. The analysis of the 8-9 september 2002 rain estimates shows that the event is particularly remarkable by its spatial extent. It also presents a marked space-time structure which has certainly been influential in the flash flood and flood genesis over the affected region.