MM-6 (6/29/05 version)
Watershed Restoration And Protection Strategies: Impervious Surfaces
Impervious surface percentages, as shown in item F of Figure 1, fundamentally impact the
stream flow regime and therefore impact both overland pollutant transport and stream integrity. Specifically, the Center for Watershed Protection (CWP) has documented that adverse impacts to stream integrity can occur with as little as 10% impervious surface in a watershed. Once 25% impervious surface occurs, full restoration of stream integrity may not be possible technically and/or economically.
Consequently, it is important to include this component in any watershed-based assessment prior to developing watershed management objectives and selecting applicable management practice systems. This is particularly important for urbanizing watersheds (PDF 210kb) and Ohio NEMO.