Stormwater Management Techniques for Ecosystem Restoration using Flow Regime Improvements

Abstract

This study demonstrates how stormwater management techniques can produce ecosystem restoration through flow regime restoration. The study acknowledges other factors, such as water quality and habitat influence ecosystem restoration, but focuses upon hydrology restoration for overall watershed restoration guidance. The study uses established relationships between flow regime and watershed characteristics to set a flow restoration target consistent with a healthy aquatic community. By focusing on two urbanized watersheds in the Great Lakes, BMP performance comparisons were made. For example, conventional stormwater management was compared with Low Impact Development (LID). General guidelines on flow regime restoration potential were developed based on watershed characteristics.A methodology for quantification of watershed restoration needs was derived based on calculating the BMP volume needed to meet flow regime restoration targets. Further BMP prioritization focused upon a method to value additional BMP benefits (water quality, habitat, etc.). Finally, potential BMP implementation incentives were summarized.The findings indicate that BMP implementation can significantly improve the flow regime in urbanized watersheds. The flow regime restoration can complement other watershed management objectives such as non-point source water quality improvements, CSOs, and increased habitat value. KEYWORDSFlow regime, BMP, stormwater retrofits, flow duration curve, watershed modeling, ecosystem restoration, low impact development, ecological metric INTRODUCTIONHistorically, watershed management has focused on meeting water quality standards through the control of point and non-point source discharges, including stormwater. The basis for water quality standards and discharge limits has assumed that these conditions would be supportive of designated uses, in particularly aquatic life. However, examples exist of watersheds where significant water quality improvements have been made, yet comparison with aquatic life conditions in reference watersheds indicates that the desired ecological endpoint is still far from being achieved. Consequently, it became readily apparent that other factors important to ecosystem health are not being addressed. In particular, a suitable hydrologic regime is essential for a stream to support aquatic life because it influences the reproductive and survival mechanisms of fish and affects a number of other factors including geomorphology, habitat, and water temperature. Therefore, effective watershed management needs accessible tools that can