Rainfall and development of floods

Rainfall through flood generation plays a crucial role in the hydraulic structure designing and in the management of the water resources supplied as river discharge to the reservoirs. It is therefore useful to understand those processes that contribute to the formation of floods through the transformation from rainfall into discharge. Both significant floods produced by specified observed rainfall distributions and possible extreme floods generated by hypothetic heavy rainfalls are of primary interest. In this context, the outlines of the time evolution of the discharge associated to a typical event with significant rainfall occurred over a given watershed are analyzed and a recognized rainfall-runoff model framework for simulation and real-time forecast of floods is formulated. This model, of semi-distributed type, is then integrated by specific representations of the implicit incorporated physical processes. Furthermore, a classical approach for determining design floods is described starting from extreme rainfalls, deduced by statistical analysis. It consists of deriving an extreme rainfall pattern approximated as homogeneous through the whole watershed then applied as input to the above model in the version for flood simulation.