The Sediment Workgroup has been sunsetted. When active the Sediment Workgroup provided technical and policy-related assistance to the Chesapeake Bay Program partners to meet Chesapeake 2000 sediment goals. Objectives wereto:
The primary objective of this report is to provide a review of the literature on the sources, transport, and delivery of sediment in Chesapeake Bay and its watershed with discussion of potential implications for various management alternatives. The authors of the report have extracted, discussed, and summarized the important aspects of sediment and sedimentation that are most relevant to the CBP and other sediment related-issues with which resources managers are involved.
Sediment is the third biggest pollutant to the Bay and its tributaries. Tidal sediment comprises approximately 57% of the sediment load to the Bay. Excess sediment is a key contributor to degraded water clarity and damages critical habitats (e.g. SAV beds and oyster bars) and living resources (shellfish, finfish and waterfowl). This report provides information on important tidal sediment processes and factors to consider before undertaking shoreline management actions to reduce tidal sediment loads. It provides maps and other general data to help target problem areas and identify valuable living resources where sediment reduction activities could help improve water clarity.
The Chesapeake Bay Program (CBP) hosted a workshop in Annapolis, Maryland on February 24-25, 2003, at which sediment experts shared information related to sediment best management practices (BMPs). The information presented on selected BMPs has been summarized in this document, and is intended to assist the CBP’s Sediment Workgroup (SedWG) and others as they move to the next generation of sediment controls and other practices to improve water clarity in riverine, tidal and near shore areas. In order to provide a thorough summary of each BMP to the workgroup, experts from within the CBP community have contributed to the presenters’ information. Each final BMP summary has received the approval of the expert who presented the information at the workshop.
Suspended sediment is identified as one of several factors that contribute to decreased water clarity and subsequent stress on the SAV in the near-shore area of the Bay. There are many complex, poorly understood processes which impact transport of the finest sediments in an estuarine environment. It is these finest sediment particles that cause water clarity impairments. To determine the source of the sediment impacting water clarity a “sedimentshed” concept is applied. The sedimentshed is defined as the area, including upland, near-shore and sub-aqueous areas that contributes the sediment load that directly influences water clarity in SAV growing areas. The determination of sedimentsheds are expected to play a critical role in understanding where sediment originates and aid in setting an appropriate geographic frame of reference for setting/revising sediment cap allocations by 2010.
This document synthesizes sediment research needs through February 2007. Findings from these research projects should help address the numerous sediment information gaps discussed during the STAC 2007 Sedimentsheds Workshop and also identified in “A Summary Report of Sediment Processes in the Chesapeake Bay and Watershed”.
The “ultimate” long-term source of sediment in the Chesapeake Bay watershed has historically been hillslope erosion. This remains true in the contemporary landscape. Erosion and the resultant sediment loadings generated within and moving out of the watersheds draining to the Chesapeake Bay remain problematically high. They are not only high during periods of urban construction and on actively tilled cropland, but can also be found to exceed estimated historic “background” erosion rates in all land cover conditions and lithologic settings within the region. This trend is partly due to the effects from historic episodes of anthropogenic disturbance in many locations. The contemporary erosion rates carry economic costs in terms of agricultural land conservation and stream management, and can create problematic conditions for aquatic communities and downstream depositional environments, including the Chesapeake Bay.