Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

While the GUEST erosion prediction framework has been applied and tested under experimental and field conditions, computer programs to model erosion and deposition have not been widely available, especially for multi-size sediment sorting during deposition. GUSED (Griffith University Soil Erosion and Deposition) is a physically based model that predicts runoff, soil loss, sediment transport and deposition along arbitrarily defined hillslopes under steady state conditions. GUSED can model straight, concave, and convex slopes, slope discontinuities, converging and/or diverging flow pathways, and multi-size erosion and deposition, pollutant enrichment processes, and spatially distributed parameters. A powerful numerical solver for systems of ordinary differential equations was implemented to deal with a wide range of settling velocity characteristics. This paper presents key algorithms implemented and some results from limited validation trials of the hillslope erosion and deposition module. Model predictions were compared with observations and measurements made in two published laboratory experiments with a focus on the sediment delivery ratio (SDR, the ratio of sediment delivered from a defined area to the gross erosion from that area). Compared to the observed SDR as a function of unit discharge (Beuselinck et al., 1999), GUSED is able to reproduce the relationship between unit discharge and SDR for individual size classes (Figure 1). It is also noted that with an abrupt reduction in slope steepness, both observed and predicted SDR are less sensitive to inflow sediment concentration than to unit discharge, and hence to the stream power. In the second comparison, GUSED predicts sediment deposition observed along a concave slope (Davis, 1978). For both sand and coal used in the experiment, GUSED is able to reproduce the observed onset of deposition and the pattern of deposition along the concave profile. Predicted SDR is systematically lower than observed SDR because GUSED assumes steady-state conditions, while observed sediment delivery through the concave profile increases over time as deposited sediment accumulates on the lower part of concave slope (Davis, 1978). In conclusion, GUSED has been tested and validated using published experimental data. It was also noted through this validation exercise that for erosion modeling, changes to micro-topography may be ignored; for deposition modeling, however, changes to micro-topography as a result of deposition, are too large in relative terms to be ignored. This feedback mechanism needs to be built into deposition models to obtain meaningful simulation results.