Estimation of flash flood potential for large areas

A methodology for determining the potential for flash floods in small basins within large geographical areas is presented. Geographical Information Systems (GIS) technology is used to assimilate digital spatial data, remotely sensed data, with physically-based hydrologic-hydraulic models of catchment response. The methodology uses digital terrain elevation data, digital river reach data, and the US Geological Survey land- use and land-cover data to produce estimates of the effective rainfall volume of a certain duration required to produce flooding in small streams. This flood potential index is called threshold runoff. For operational application, soil water accounting models are used to yield estimates of effective precipitation over areas of 1000 km2. Maps of flash flood potential can then be constructed using remotely-sensed and on-site data. Examples of application in various regions of the USA are discussed.