Upland Erosion Modeling

Abstract

Significant advances in upland erosion modeling have been achieved in the past decade. The TREX (Two-dimensional Runoff, Erosion, and Export) watershed model has been developed at Colorado State University for the simulation of surface runoff from spatially and temporally distributed rainstorms on watersheds. The model has been applied in several countries with different climatic conditions. TREX can calculate surface infiltration, surface runoff, sediment transport, and the partition of metals in dissolved, adsorbed, and particulate form. The focus of this chapter is on the calculation of surface flows and total suspended solids at the watershed scale. The chapter is comprised of three parts: (a) a description of the main processes and governing equations, (b) a description of the model components and algorithms, and (c) an application example on a large watershed. The application example for Naesung Stream in South Korea provides powerful visual evidence of upland erosion processes at the watershed scale during large rainstorms (300 mm of rainfall). Model calibration was successful and overall model performance is acceptable. Hydrologic simulation results were in good to very good agreement with measured flow volume, peak flow, and time to peak at the watershed outlet as well as several stations within the watershed. Sediment transport simulation results were also in reasonable agreement with the measured suspended solids concentration.