Physically based modelling of sediment generation and transport under a large rainfall simulator

Abstract

Abstract:A series of large rainfall simulator experiments was conducted in 2002 and 2003 on a small plot located in an experimental catchment in the North Island of New Zealand. These experiments measured both runoff and sediment transport under carefully controlled conditions. A physically based hydrological modelling system (SHETRAN) was then applied to reproduce the observed hydrographs and sedigraphs. SHETRAN uses physically based equations to represent flow and sediment transport, and two erodibility coefficients to model detachment of soil particles by raindrop erosion and overland flow erosion. The rate of raindrop erosion also depended on the amount of bare ground under the simulator; this was estimated before each experiment. These erodibility coefficients were calibrated systematically for summer and winter experiments separately, and lower values were obtained for the summer experiments. Earlier studies using small rainfall simulators in the vicinity of the plot also found the soil to be less erodible in summer and autumn. Limited validation of model parameters was carried out using results from a series of autumn experiments. The modelled suspended sediment load was also sensitive to parameters controlling the generation of runoff from the rainfall simulator plot; therefore, we found that accurate runoff predictions were important for the sediment predictions, especially from the experiments where the pasture cover was good and overland flow erosion was the dominant mechanism. The rainfall simulator experiments showed that the mass of suspended sediment increased postgrazing, and according to the model this was due to raindrop detachment. The results indicated that grazing cattle or sheep on steeply sloping hill-country paddocks should be carefully managed, especially in winter, to limit the transport of suspended sediment into watercourses.

Predicting Impacts of Land Use and Climate Change on Erosion and Sediment Yield in River Basins Using SHETRAN

“…Wicks et al, 1992;Adams & Elliott, 2006). The soil erodibility coefficients k r and k f increase in value as the soil becomes easier to erode (i.e.…”

“…Thus Bathurst et al (1996) found that conductivities evaluated at the plot scale could be successfully applied with a model grid spacing of 2 km for the 701 km 2 Cobres basin in Portugal. Likewise Adams and Elliott (2006) calculated different coefficient values for the more and less erodible conditions of winter and summer respectively. However, for basins with hilly terrain, experience is that model conductivity values are relatively high compared with point measurements (e.g.…”

Dynamic analysis of groundwater discharge and partial-area contribution to Pukemanga Stream, New Zealand

“…Figure 1 shows ground elevations along a transect of the main channel of the Pukemanga Catchment and the locations of monitoring devices. A 1050 m 2 sub-area of the catchment was the subject of experimental studies of runoff processes under a large rainfall simulator (Adams et al, 2005;Adams and Elliott, 2006;Müller et al, 2006).…”

The effects of soil properties on the turbidity of catchment soils from the Yongdam dam basin in Korea

“…The transport of suspended solids from storm runoff and their environmental impact has been widely discussed (Zonta et al 2005;Adams and Elliot 2006). However, little effort has been devoted to evaluating the contribution of the mineral composition of the actual soils to their settling behavior.…”