Is Impervious Cover Still Important? A Review of Recent Research

A presentation at the 2nd Symposium on Urbanization and Stream Ecology, May 2008.

The Impervious Cover Model (ICM) has attracted considerable attentionin recent years, with nearly 250 research studies testing its basichypothesis that the behavior of urban stream indicators can bepredicted on the basis of the percent impervious cover (IC) in theircontributing subwatershed. The majority of research published since2003 has confirmed the basic premise of the ICM, but has also revealedimportant caveats and limitations to its application, and tested thepossible effect of watershed treatment, such as stormwater treatmentpractices and riparian forest cover. The ICM continues to be a usefulplanning and forecasting tool, and provides a useful foundation fordesigning regional subwatershed management classification systems. Thepaper concludes with recommendations for improving the consistency offuture stream research studies, and testing the watershed treatmenthypothesis.