A1 Floods

Title

Floods occur when a river's flow or volume of surface runoff exceeds the carrying capacity of the natural channel or local topography, overflowing into the floodplain. The process integrates precipitation, soil infiltration and the hydrological response of the basin. Flash floods respond within minutes to hours in small, impermeable basins, while slow floods persist for days or weeks in large basins. Pre-saturation of the soil is the most important amplifying factor: it dramatically increases the fraction of rainfall that becomes runoff. The flood hydrograph (ascensopicorecession) is the time imprint of the process. The Saint-Venant equations govern downstream flood wave flow, and the kinematic wave model is its most widely used operational simplification. Prediction requires combining rainfall-runoff models with 1D/2D hydraulic models.

ID:494