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Science Summary—Sediment and Nutrient Trapping in the Flood Plain of Difficult Run, Virginia, and Implications for the Restoration of Chesapeake Bay

Prepared by Gregory B. Noe, Cliff R. Hupp, Edward R. Schenk, and Nancy R. Rybicki, U.S. Geological Survey
(Released June 2013) (PDF Version)

Fig 1 and link to larger image.


As the largest and most productive estuary in North America, Chesapeake Bay is a vital ecological and economic resource. The bay and its tributaries have been degraded in recent decades, however, by excessive inputs of nutrients (nitrogen and phosphorus) and sediment, causing poor water-quality conditions for fish and wildlife. Nitrogen and phosphorus cause algae blooms, fish kills, and poor water quality, whereas large amounts of sediment bury oyster beds and destroy young fish habitat, in addition to causing other adverse effects. A Total Maximum Daily Load (TMDL) has been established to reduce nutrient and sediment inputs to the bay (U.S. Environmental Protection Agency, 2010). As part of its scientific efforts in support of the restoration of Chesapeake Bay, the U.S. Geological Survey (USGS) is working with partners to improve the understanding of the sources, storage, and transport of nutrients and sediment to help resource managers select and implement the most effective management practices (Phillips, 2011).

Role of Flood Plains in Trapping Nutrients and Sediment

Flood plains naturally intercept and trap contaminants that are transported in streams, including nutrients and sediment, and help protect sensitive downstream ecosystems. Flood plains in the part of the Chesapeake Bay watershed that lies in the Coastal Plain Physiographic Province (fig. 1) are effective at removing much of the streams’ load of nitrogen, phosphorus, and sediment before it reaches the bay (Noe and Hupp, 2009); however, the source of most of the river sediment in the bay watershed is the Piedmont Physiographic Province, which is upstream from the Coastal Plain (Gellis and Brakebill, 2012; Gellis and others, 2009). To help resource managers consider and implement actions to meet the TMDL, scientists are working to determine (1) whether flood plains in urban Piedmont areas effectively trap contaminants, and (2) whether flood plains can be managed to increase their contaminant-trapping capacity.

Much of the sediment that was eroded from uplands and streambanks in the past, known as “legacy” sediment, is still stored in the flood plains of the Chesapeake Bay watershed (Meade and others, 1990). Erosion is a constant process in uplands and the streambanks of flood plains. Knowing where rates of erosion exceed rates of deposition in stream and river valleys allows resource managers to tailor specific management actions to the right places in order to have the greatest impact on reducing the contaminant load. Other questions that need to be answered include whether flood plains trap nutrients in addition to sediment and, if so, whether the nutrients remain trapped for extended periods or whether they are quickly recycled back to the stream. This information will help resource managers and policy makers understand the sources, transport, and retention of contaminants in the bay watershed and ultimately will provide them with the information needed to improve downstream water quality.

USGS Studies of Flood Plains in an Urban Area

In an effort to address these questions, the USGS is studying a small, urban watershed, Difficult Run, in the part of the Chesapeake Bay watershed that lies within the Piedmont region in Virginia (fig. 1). The watershed is being used as a laboratory to help Fairfax County, Virginia, identify appropriate management actions, determine their effectiveness, and optimize efforts to improve water quality. The USGS is also working with partners to study sediment and nutrient sources, storage, transport, and changes in other small watersheds. The results will help resource managers consider and implement management practices in suburban and agricultural areas to address the bay TMDL.

This Science Summary is one in a series that is designed to facilitate the understanding and application of results of relevant USGS studies by Chesapeake Bay resource managers and policy makers. It presents a brief overview of the most recent published work by the USGS and its collaborators on the role of flood plains in reducing the load of nutrients and sediment that is transported downstream to the bay; provides an understanding of how this information can be used to develop effective management policies and practices; describes the role of flood plains as a source of, and in the transport and retention of, sediment and other contaminants in Difficult Run; and includes a list of references for additional information.

The Key Findings and Implications for Management Policies and Practices and Next Steps listed below are derived from several USGS reports and other published studies.

Key Findings

Flood plains are important traps for sediment and associated nutrients

Fig 2 and link to larger image.

Large amounts of legacy sediment are stored in the Difficult Run stream valley

Implications for Management Policies and Practices and Next Steps

Fig 3 and link to larger image.

References Cited

Fry, J., Xian, G., Jin, S., Dewitz, J., Homer, C., Yang, L., Barnes, C., Herold, N., and Wickham, J., 2011, Completion of the 2006 National Land Cover Database for the Conterminous United States: Photogrammetric Engineering & Remote Sensing, v. 77, no. 9, p. 858–864, accessed May 20, 2013 at

Gellis, Allen, and Brakebill, John, 2012, Science summary—Sediment sources and transport in the Chesapeake Bay watershed: accessed March 15, 2013, at

Gellis, A.C., Hupp, C.R., Pavich, M.J., Landwehr, J.M., Banks, W.S.L., Hubbard, B.E., Langland, M.J., Ritchie, J.C., and Reuter, J.M., 2009, Sources, transport, and storage of sediment at selected sites in the Chesapeake Bay watershed: U.S. Geological Survey Scientific Investigations Report 2008–5186, 95 p. (also available online at

Hupp, C.R., Noe, G.B., Schenk, E.R., and Benthem, A.J., 2013, Recent and historic sediment dynamics along Difficult Run, a suburban Virginia Piedmont stream: Geomorphology, v. 180-181, p. 156-169, available online at,

Meade, R.H., Yuzyk, T.R., and Day, T.J., 1990, Movement and storage of sediment in rivers of the United States and Canada, in Wolman, M.G., and Riggs, H.C., eds., Surface water hydrology--The geology of North America: Boulder, Colorado, Geological Society of America, p. 255-280.

Merritts, Dorothy, Walter, Robert, Rahnis, Michael, and Hartranft Jeff, and others, 2011, Anthropocene streams and base-level controls from historic dams in the unglaciated mid-Atlantic region, USA: Philosophical Transactions of the Royal Society A, v. 369, no. 1938, p. 976-1,009, doi: 10.1098/rsta.2010.0335.

Noe, G.B., and Hupp, C.R., 2009, Retention of riverine sediment and nutrient loads by coastal plain floodplains: Ecosystems, v. 12, no. 5, p. 728-746, DOI: 10.1007/s10021-009-9253-5 available online at

Noe, G.B., Hupp, C.R., and Rybicki, N.R., 2013, Hydrogeomorphology influences soil nitrogen and phosphorus mineralization in floodplain wetlands: Ecosystems, v. 16, p. 75-94, DOI: 10.1007/s10021-012-9597-0.

Phillips, S.W., 2011, USGS science for the Chesapeake Bay restoration: U.S. Geological Survey Fact Sheet 2010–3081, version 1.0.1, 2 p. (also available at

Schenk, E.R., Hupp, C.R., Gellis, A.C., and Noe, G.B., 2012, Developing a new stream metric for comparing stream function using a bank-floodplain sediment budget: a case study of three Piedmont streams: Earth Surface Processes and Landforms, DOI: 10.1002/esp.3314 available online at

U.S. Environmental Protection Agency, 2010, Chesapeake Bay TMDL, Final Bay TMDL documents, Executive summary and appendices: accessed September 20, 2011, at

Suggested citation:

Prepared by Noe, G. B., Hupp, C. R., Schenk, E. R., and Rybicki, N. R., 2013, Science summary—Sediment and nutrient trapping in the flood plain of Difficult Run, Virginia, and implications for the restoration of Chesapeake Bay: available online only at

For additional information about this research, please contact Gregory B. Noe (, Cliff R. Hupp (, Edward R. Schenk (, or Nancy R. Rybicki (

For additional information about USGS Chesapeake Bay studies, please contact Scott Phillips (

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