Long-term sediment deposition in the riparian zone of a coastal plain watershed

Sediment deposition from 1880 to 1979 was estimated for the riparian zone of a coastal plain agricultural watershed. Two approaches were used: (1) deposition estimates based on changes in depth to the argillic horizon along transects from fields to streams and (2) calculations of mass of deposition derived from estimated 100-year upland erosion based on the universal soil loss equation and a sediment delivery ratio. Estimates of changes in depth to the argillic horizon along nine transects yielded a mean of 52 Mg·ha·−1yr−1, with a range 7.6 to 92 Mg·ha·−1yr−1. The estimated average annual rate of gross erosion minus sediment transport from the watershed was 35 Mg·ha·−1yr−1. Thus, the average annual rate of sediment deposition on this watershed during the 1880-1979 period was 35 to 52 Mg·ha·−1yr−1. These data suggest that riparian ecosystems are important sinks for sediments.