Assessment of Stream Restoration for Reduction of Sediment in a Large Agricultural Watershed

摘要

In many agricultural watersheds, channel erosion is a major source of sediment. In these watersheds, a comprehensive approach to reducing channel erosion can aid in the feasibility of meeting water quality goals. In the Minnesota River Basin (MRB), a large agricultural watershed, increased peak flows have contributed to greater sediment loading from within the channel. This study focuses on three components of channel restoration that are important in developing a strategic framework: sediment source reduction, working with private landowners, and the economics of restoration. A synthesis of sediment research was done to assess the sediment reduction benefit of restoration projects. While field erosion is the largest source of gross erosion, most of the sediment from fields is not delivered to the river. In the MRB, sediment from stream banks and bluffs is the dominant source, thus requiring water storage and/or stream management in order to reduce sediment load. Landowners favored edge-of-field practices that minimize the conversion of farmland and have minimal government intervention. Economic analysis of restoration showed that the most cost-effective restoration projects reduced large amounts of sediment on short stretches of lower-order streams. However ecological benefits, project sustainability, and local cultural issues suggest a role for smaller stream restoration projects. Sediment reduction estimates and assessment of ecosystem service benefits from stream restoration projects need to be further developed.