Quantifying Runoff Generation

Flash flooding is a hazard in many parts of the world. In south Louisiana, the terrain is particularly flat with minimal natural slope to support efficient drainage. Flash flooding is common in urban areas where runoff from rainfall quickly accumulates in coulees and cannot drain fast enough. A flash flood is a sudden and rapid rise in stream water depth resulting from heavy, localized rainfall. With a growing population, developing neighborhoods in terrain susceptible to flash floods has become more common and therefore increased the potential for damage to private property and public infrastructure.

Hydrologists are frequently required to design flood protection infrastructure to protect people and property from the impacts of flash flooding. An important hydrologic question in designing for flood protection is: How much streamflow occurs in a river in response to a given amount of rainfall? To answer this question we need to know where water goes when it rains, how long does water reside in a watershed, and what pathway does water take to the stream channel. This module addresses these questions and also looks at how much runoff is generated from surface water input comprised of rainfall.