Conceptual Ecological and Physical Framework for Evaluating Receiving Water Impacts

A conceptual framework is presented that incorporates disparate information to determine the impacts to receiving waters. The framework is then applied using actual data from various subwatersheds in Baltimore County, Maryland to evaluate the respective significance of the input data at determining the objectives and goals for each receiving water and to design the process for developing watershed management plans. Using an established framework, such as presented here, provides the watershed managers with a defensible tool for characterizing and classifying receiving waters. It then guides the managers on the types and detail of the data needed during subsequent stages to identify, screen and select measures for mitigating existing receiving water impacts and managing potential future impacts. The framework incorporates information such as ecological, physical, water quality and Geographic Information System planimetric data, as well as existing land uses and proposed conditions. While land use practices govern the change in storm water runoff characteristics, the resultant impact to receiving streams differs. Studies in the Mid-Atlantic region, and nationwide, have indicated that local variables such as the sensitivity of the ecology and geomorphology interact with the degree of development, land use practices and existing management practices to create a broad range of impacts to receiving waters. The framework establishes a flow chart approach using metrics for evaluating the relative impacts to the receiving waters and deterring the causes.