Analysis of Fluvial Suspended Sediment Load Contribution through Anthropocene History to the South Atlantic Bight Coastal Zone, U.S.A.

Discerning the effects of anthropogenic activities (i.e., reservoir construction, land use change), as opposed to those of natural processes (i.e., climate variability), on suspended sediment flux has become an increasingly difficult challenge. This contribution presents water and suspended sediment flux from five major watersheds that discharge into the southeastern U.S. Atlantic, a region that is currently considered sediment starved. Three periods of Anthropocenetime were defined and evaluated: (1) “pre-European conditions” (1680–1700), (2) “pre-dam conditions (1905-1925), and (3) post-dam conditions (1985-2005). Physical and hydrologic watershed data were used to run a climate-driven hydrological transport numerical model (HydroTrend) to estimate suspended sediment flux for each period. Results indicate that the suspended sediment contribution to the South Atlantic Bight coastal zone increased by up to 145% as a result of accelerated soil erosion conditions caused by the arrival of European settlers and has since declined by approximately 55%, primarily because of the construction of large resevoirs. This trend suggests a return to pre-European sediment yields, approximately 100 years after historic peak of soil erosion in the southeastern Piedmont. Our results indicate that variations in sediment yield between time periods are primarily caused by direct anthropogenic forcings, while climate changes over the periods considered have played an insignificant role