MAPPING VULNERABILITY TO UPLAND EROSION IN THE CHESAPEAKE BAY.pdfVIP

2nd Joint Federal Interagency Conference, Las Vegas, NV, June 27 - July 1, 2010       MAPPING VULNERABILITY TO UPLAND EROSION IN THE CHESAPEAKE BAY WATERSHED Scott W. Ator, Research Hydrologist, U.S. Geological Survey, Baltimore, Maryland, swator@; John W. Brakebill, Geographer, U.S. Geological Survey, Baltimore, Maryland, jwbrakeb@; Gregory E. Schwarz, Economist, U.S. Geological Survey, Reston, Virginia, gschwarz@ Abstract  Management of suspended sediment in large watersheds is complicated by the complexity and spatial variability of landscape factors affecting sediment supply and transport. SPAtially Referenced Regressions on Watershed attributes (SPARROW) is a spatially explicit mass-balance watershed modeling technique that uses nonlinear regression equations to relate stream constituent flux to land and stream sources and transport factors. A calibrated SPARROW model was used to illustrate the cumulative effects of interacting landscape factors on sediment transport from uplands to stream corridors in the Chesapeake Bay watershed. Suspended- sediment transport to Chesapeake tributaries is observed to be more efficient in steeper areas with relatively impermeable soils and few impoundments. Sediment delivery to streams also is greater in the Piedmont Uplands than in other physiographic settings. Relatively erosive soils and high suspended-sediment yields have previously been reported in this region; however, the SPARROW model indicates that these yields are influenced by factors independent of slope and soil permeability. The cumulative