Best Management Practices for Sediment Control and Water Clarity Enhancement

摘要

Sediment is generated by natural weathering of rocks and soils, accelerated erosion of lands, streams and shorelines caused by agricultural and urban development, and resuspension of previously eroded sediments that are stored in stream corridors and in the Chesapeake Bay. Sediment is composed of loose particles of clay, silt and sand. Major sediment sources in the Chesapeake Bay watershed include upland or watershed surfaces and stream corridors. Along the Bay's shoreline, the primary sources of sediment are from tidal erosion (shoreline erosion, near-shore erosion and near-shore resuspension), ocean input, and biological production. It is estimated that watershed sources contribute approximately 61 percent of the sediment load to the Bay, tidal erosion 26 percent and oceanic input the remaining 13 percent. It is estimated that approximately 8.5 million metric tons of sediment enters the Bay each year. Excess suspended sediment is one of the most important contributors to degraded water quality and has adverse effects on critical habitats and living resources in the Chesapeake Bay and its watershed. Sediment suspended in the water column can reduce water clarity and increase light attenuation such that light penetration is below that needed to support healthy submerged aquatic vegetation (SAV). SAV beds are an important biological resource in estuaries, providing critical habitat and influencing the physical, chemical, and biological conditions of the estuary.