A watershed scale numerical model of the impact of land use change on bed material transport in suburban Maryland, USA

摘要

We predict changes in bed elevation and grain size composition caused by urbanization from 1952 to 1996 in the channel network of the Good Hope Tributary watershed. We developed methods for predicting the influence of urbanization on the 1.5-year peak discharge, the annual sediment supply to the network, and sediment production caused by channel enlargement. The model was calibrated to reproduce bed material yield estimated from a sediment budget. Development caused channel width to increase by a factor of 1.7, and discharge, upland sediment supply, and bed material yield approximately doubled. The longitudinal profile became smoother, and the bed coarsened. After 1996, model boundary conditions were held constant and the simulation continued through 2042. The bed continued to coarsen, and the yield of bed material gradually declined. Sediment production did not approach a steady state value, suggesting that geomorphic recovery from urbanization may require more than 50 years.