Maps

Over the past decade, none of the monitoring sites in the Chesapeake Bay watershed have shown improving flow-adjusted trends in sediment concentrations. Between 2004 and 2013: zero sites have shown improving trends for sediment concentrations. Four sites—including the Appomattox, Choptank, Pamunkey and Patuxent rivers—have shown degrading trends. Five sites—including the James, Mattaponi, Potomac, Rappahannock and Susquehanna rivers—have shown minor changes that are not statistically significant.

One-third of the monitoring sites in the Chesapeake Bay watershed show improving long-term flow-adjusted trends in suspended sediment concentrations. Between 1985 and 2013: three out of nine sites—including the Choptank, Patuxent and Potomac rivers—have shown improving trends for sediment concentrations. One site—the Pamunkey River—has shown degrading trends. Five sites—including the Appomattox, James, Mattaponi, Rappahannock and Susquehanna rivers—have shown minor changes that are not statistically significant.

Watershed Yield: Sediment yields ranged from 9.3 to 648 tons per square mile. Each of the 17 sites in the high yield category carries more than 200 tons of sediment per square mile of watershed. High yielding sites are spatially dispersed across the Susquehanna, Potomac and Rappahannock watersheds. The lowest sediment yielding sits are located on the Eastern Shore and the York River Basin.

Short Term Trend: Over the past 10 years, 49 percent of sites show little change while 41 percent show degrading flow-adjusted sediment concentrations. Between 2003 and 2012: - 4 out of 39 sites show improving flow-adjusted trends for sediment concentrations, - 16 site shows degrading trends, and - 19 sites show small changes that are not statistically significant.

Long Term Trend: Forty-four percent of long-term stream monitoring sites in the Chesapeake Bay Watershed show little change in flow-adjusted concentrations of sediment. The remaining sites were evenly split between improving and degrading conditions. Between 1985 and 2012: - 8 out of 29 sites show improving flow-adjusted trends for sediment concentrations, - 8 sites show degrading trends, and - 13 sites show small changes that are not statistically significant.

Average yields for total sediment (TS) were estimated for the last five years at 65 sites and classified into thirds as high, medium, and low. While the distribution was spatially variable, there were some general patterns in location. Generally, spatial patterns not very discernible for sediment except for higher yields in the middle of the watershed, areas where total nitrogen and total phosphorus yields are also highest. The lowest yields are generally in the western areas of the Bay watershed, an area dominated by forests and on the Eastern Shore of Maryland and Delaware.

Over the past 10 years, the majority of sediment concentration trends are non-significant monitoring at sites within the Bay watershed with many sites showing degrading condition and only a few are improving. The trend results indicate that at some monitored locations, short-term trends indicate that management actions, such as efforts to curb erosion and runoff have reduced concentrations of sediment. While these reductions provide evidence of improving conditions in some upstream areas, additional reductions will be needed to have healthier streams and meet water-quality goals for the Bay.

Changes in suspended sediment concentrations have been determined for the period 1985-2011 at 31 stream sites in the Chesapeake Bay watershed. Of these, 14 sites show trends that were not statistically significant, 9 sites show improving trends, and 8 sites show degrading trends.

Long-Term Flow-Adjusted Concentration Trends for Suspended Sediment for 31 Sites in the Chesapeake Bay Watershed, 1985-2010

This map is a key to monitoring stations used to depict flow-adjusted concentration data for nitrogen, phosphorus, and sediment.