SIMULATION AND PREDICTION OF SEDIMENT DYNAMICS AT UPPER SANGAMON RIVER BASIN THROUGH COUPLING OF THREW AND 3ST1D MODELS

Simulation and prediction of sediment dynamics have received increasing attention as the awareness of the human impact on sediment dynamics grows. In intensively managed landscapes, human activity has significantly altered the hydrological and biogeochemical cycles within terrestrial and aquatic ecosystems. Thus, understanding and predicting the response of sediment dynamics to human impact are crucial to developing management strategies for reducing the vulnerability of the ecosystem to future changes.

The main objective of this study is to simulate and predict the spatial and temporal patterns of sediment dynamics at Upper Sangamon River Basin, Illinois. The 3,690-km² Upper Sangamon River Basin is characterized by low-relief, agricultural lands dominated by row-crop agriculture. This study conceptualizes the basin as a collection of reaches, or representative elementary watersheds (REW), that are connected to each other through the river network. The REWs reflect the landscape heterogeneity and various agricultural practices within the watershed. Each REW comprises a lumped representation of a hillslope and channel component. The semi-distributed THREW model is capable of simulating hillslope hydrological and sediment processes; the one-dimensional 3ST1D model is used to calculate flow and sediment transport within channels. The integration of two models yields good estimates of sediment export patterns at Upper Sangamon River Basin. Our preliminary results indicate that spatial heterogeneity of the sediment supply sources is an important factor that controls sediment dynamics along the stream network. Among the sediment supply sources, agricultural lands are identified as the dominant contributors to sediment yields at watershed outlet.