Sediments are a problem in the Bay because they can:
- Smother bottom-dwelling plants and animals, such as oysters and clams.
- Become suspended in the water column, making the water cloudy so less light is available for underwater bay grasses.
- Carry high concentrations of certain toxic chemicals that contaminate waterways.
- Carry nutrients, particularly phosphorous, which increase nutrient pollution in the Bay.
- Accumulate in ports and waterways.
Most of the sediment delivered to the Bay comes from:
Learn more about sediment.
Based on long-term average hydrology simulations, it is estimated that 4.8 million tons of sediment were delivered to the Bay’s tidal waters in 2007, compared to 5.9 million tons in 1985.
Loads are simulated based on reported implementation of best management practices (BMPs) that reduce sediment pollution. The simulation removes annual hydrological variations to measure the effectiveness of BMP implementation and converts the numerous BMPs, which have various pollution reduction efficiencies depending on type and location in the watershed, to a common currency of sediment reduction.
Agricultural Land
Approximately 2.9 million tons, or 60 percent of the total sediment load to the Bay, is due to runoff from agricultural areas.
These detrimental loads to the Bay could be reduced by using BMPs that prevent sediment from reaching local waterways that lead to the Bay.
Urban/Suburban Runoff and Legacy Sediment
Approximately 900,000 tons, or 19 percent of the total sediment load to the Bay, is due to runoff from urban and suburban areas and legacy sediment in stream channels from deposits that occurred during the conversion of forest land to agricultural and urban land uses.
These detrimental loads to the Bay could be reduced by using BMPs that prevent any sediment from reaching local waterways that lead to the Bay.
Natural
Approximately 1 million tons, or 21 percent of the total sediment load to the Bay, is due to natural sources such as forests.
Sources Not Accounted For in the Chart
Tidal shoreline erosion is also a significant source of sediments to the Bay, but is not accounted for in the chart.
For more information contact:Jeff Sweeney at 800-968-7229 ext. 844
Chesapeake Bay Program Phase 4.3 Watershed Model 2007 Simulation