Research Areas > Stormwater > Hydromodification

Research Area: Hydromodification

The process of urbanization has the potential to affect stream courses by altering watershed hydrology and sediment-transport patterns. Development can increase the amount of impervious surfaces on formerly undeveloped landscapes. This reduces the capacity of the remaining pervious surfaces to capture and filter rainfall. As a result, a larger percentage of rainfall becomes runoff during any given storm. Subsequently, runoff reaches stream channels much more quickly, and peak discharge rates are higher than before development for the same size rainfall event. These effects have been termed hydromodification.
 

SCCWRP Research

The goal of current SCCWRP research is to develop a series of tools supporting implementation of hydromodification management measures. Successful implementation of these measures requires an understanding of the mechanisms by which hydromodification affects the physical, chemical, and biological integrity of streams.

Past SCCWRP research has consisted of empirical analysis and some modeling to better characterize the relationship between changes in impervious cover and changes in stream geometry in southern California's ephemeral and intermittent streams. These studies have shown that streams in semi-arid climates tend to be more susceptible to the effects of hydromodification than those in more humid regions. However, the response in any particular stream is dependent on a variety of factors, and hence is difficult to predict.
 

SCCWRP hydromodification projects include:

• Effect of Increases in Peak Flows and Imperviousness on the Morphology of Southern California Streams
• Workshop on Managing Runoff to Protect Natural Streams
• Assessment and Management of Hydromodification Effects
• Effect of Hydromodification on Beneficial Uses