ABSTRACT Restoration resources are usually limited and strategic information on and erosion susceptible areas are required to avoid further degradation. This study has potential in the Mzimvubu River Catchment, South Africa, where two large reservoirs are planned on the Tsitsa tributary. The Tsitsa River Catchment, however, consists of highly erodible soils with widespread gully erosion evident. It is important to prevent further gully erosion in the catchment due to the presence of duplex and dispersive soils. Therefore, this study modelled areas that are susceptible to gully development in the Tsitsa River Catchment, as well as estimated the sediment yield potential from the susceptible areas if gully development occurs. This was achieved by mapping gully-free areas in a GIS that have the same DEM-derived topographical variables, soil associations and land cover as gullied areas, followed by scenario analysis of the potential sediment yield. More than 30 000 ha (7%) of the catchment is intrinsically susceptible to further gully development, consisting of drainage paths with a large contributing area and erodible duplex soils. If not protected, these susceptible areas could contribute an additional 300 million m3 of sediment to the river network, reducing the volumes of both reservoirs by more than 50%.

中文翻译：

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支持避免退化计划的沟壑侵蚀敏感性建模

摘要 恢复资源通常是有限的，需要关于易受侵蚀地区的战略信息以避免进一步退化。这项研究在南非 Mzimvubu 河流域具有潜力，那里计划在 Tsitsa 支流上建造两个大型水库。然而，Tsitsa 河集水区由高度易侵蚀的土壤组成，沟壑侵蚀明显。由于双重和分散土壤的存在，防止集水区进一步的沟壑侵蚀非常重要。因此，本研究模拟了 Tsitsa 河流域易受冲沟发育影响的区域，并估计了发生冲沟发育时易受影响区域的产沙潜力。这是通过在具有相同 DEM 派生地形变量的 GIS 中绘制无沟壑区域来实现的，土壤组合和土地覆盖作为沟壑区域，然后对潜在沉积物产量进行情景分析。超过 30 000 公顷（7%）的集水区本质上容易受到进一步沟渠开发的影响，这些沟渠由具有较大贡献面积的排水路径和可侵蚀的复层土壤组成。如果不加以保护，这些易受影响的地区可能会向河网贡献额外 3 亿立方米的泥沙，使两个水库的水量减少 50% 以上。