A rule-based soil erosion model for a hilly catchment

Catchment resources, generated from multi-source data (remotely-sensed, map- and ground-based systems), were input to a raster-based Geographical Information Systems (GIS) after geometrically co-registered to a standard grid (pixel). The GIS used was the PC-based, indigenously-developed package, called GRAM (Geo-Referenced Area Management). A set of knowledge-based rules, for assessing the soil erosion of this heterogeneous hilly catchment, were formulated from the knowledge of the multi-disciplinary resource-experts and the knowledge of the local catchment resources, in addition to the field observations. This rule-based model, which is hopefully fast and cost-effective and without effect of the individual bias, helped in inferring the erosion intensity units that most likely to occur at any given pixel in the system. Finally, the catchment was grouped into four different erosion intensity units namely very severe, severe, moderate to severe and slight to moderate. The quantitative soil loss (t ha−1 year−1) ranges, estimated by USLE model by a spatial information analysis approach (GIS), were also computed: (a) Very severe (>50): (b) Severe (40–50); (c) Moderate to severe (20–40); and (d) Slight to moderate (<20). An integrated priority delineation survey, for taking up soil/water conservation measures by Sediment Yield Index model, carried out in the catchment grouped the catchment into very high, high, medium and low priority classes. Apparently, the areal extent of high and moderate priority classes occupy about 80% of the catchment, which is closely following the areal extent of severe and moderate to severe erosion intensity unit categories by this rule-based model. The outcome of the results of this study will be immensely useful to monitor the dynamic changes in the catchment environment. The soil erosion information system thus generated, identifies the targeted problem areas for conservation planning and sustainable development of the catchment. Although it is an early airing of results obtained from this rule-based model, the introduction of multi-disciplinary expertʹs informed opinion may provide an extension to the traditional methods of assessing the soil erosion status/magnitude which should enable and/or evaluate different catchment management scenarios.