The aim of this task was to improve understanding of the major atmospheric and hydrologic factors that cause extreme flash flood events, in particular, those flood events that occur in small or medium ungauged catchments.

Various numerical experiments were undertaken to analyse the processes associated with flash flooding. Meteorological analyses were based on observations (from both radar and rain gauges) and results from high-resolution simulated rain fields (i.e. the spatial extent and intensity of a rainfall event over the time period of that event). Four different flash-flood producing storms were analysed: three in South-east France and one in the Eastern part of the Italian Alps. Several catchments in Italy, the Netherlands and Spain were studied to examine the hydrological processes associated with flash floods.

The research is intended for engineers and scientists involved with modelling flash flood events as well as those involved in flash flood risk management.

This work links closely with FLOODsite Task 16, which proposed new concepts for flash flood forecasting and Task 23, which undertook pilot studies in flash flood basins across Europe.

Key words: flash flood, hydrological and meteorological processes, modelling