Use of Radar Rainfall Estimates for Flood Simulation in Mountainous Basins

Abstract

In this paper we focus on the problem of on-line flood forecasting in small- to middle-size basins (100–1 000 km²) characterised by rugged orography. Real-time flood forecasting in these systems, which are characterised by a rapid response to rainfall, is generally driven by on-line precipitation estimation and forecasting. However, rainfall estimates at these spatial scales (which entail also short time steps, of the order of 30 minutes to 1 hour) generally cannot be provided by a telemetered rain gauge network, considering reasonable economical constraints. These conditions apply frequently when designing and implementing forecasting operational real-time hydrological systems in European countries, particularly, but not exclusively, in Mediterranean regions. Small basins in these regions generally have a marked hilly or even mountainous relief. They frequently receive heavy rainfall, since the relief is conducive to the generation of storms, which are occasionally violent and very localised. Attention to this spatial scale is becoming crucial, since forecasting systems are required to provide distributed warnings over a whole region including many basins (Lanza and Siccardi 1994).