A staggered approach to flash flood forecasting – case study in the Cévennes region

摘要

A staggered approach to flash flood forecasting is developed within theIMPRINTS project (FP7-ENV-2008-1-226555). Instead of a single solutionsystem, a chain of different models and input data is being proposed that actin sequence and provide decision makers with information of increasingaccuracy in localization and magnitude as the events approach. The firstsystem in the chain is developed by adapting methodologies of the EuropeanFlood Alert System (EFAS) to forecast flash floods and has the potential toprovide early indication for probability of flash floods at the Europeanscale. The last system in the chain is an adaptation of the data basedmechanistic model (DBM) to probabilistic numerical weather predictions (NWP)and observed rainfall, with the capability to forecast river levels up to12 h ahead. The potential of both systems to provide complementaryinformation is illustrated for a flash flood event occurred on 2 November2008 in the Cévennes region in France. Results show that the uncertaintyin meteorological forecasts largely affects the outcomes. However, at anearly stage, uncertain results are still valuable to decision makers, as theyraise preparedness towards prompt actions to be taken.