Spatial multi-criteria evaluation, digital watershed data, and GIS to soil erosion disaster mitigation by channel terracing (banquette): case study Miankouh watershed in Iran

摘要

Soil erosion is an environmental and production problem in Miankouh watershed with 61760 ha. To decrease the risk on environmental impacts, there is an increasing demand for sound, and readily applicable techniques for soil conservation planning in this watershed. The objective was to select sites most suitable for channel terracing or banquette in order to soil loss disaster mitigation by application of digital earth data and Water Erosion Prediction Model (WEPP)in a geographic information systems (GIS)environment. Data used for the WEPP were either determined or taken from published literature pertaining to the Miankouh watershed. By means of WEPP, layer of soil erosion disaster was built. Other layers include factors and constraints such as slope, land use, vegetation Index, geology and geomorphology, soil, proximity to road, to Qanat, to well, to village was prepared as spatial digital watershed data. ILWIS, GIS software was used to weight, to standard and to combine the digital layers. A criteria tree model of factors and constraints was built then used Spatial Multi-Criteria Evaluation (SMCE)to make composite index map. The study revealed that the annual average soil loss rate in the watershed was high, whereas sediment yield was low and there were local problems on the some slopes. In the watershed, 658 ha of agricultural land had slopes >40% and should be reforested by channel terracing. This area was considered as an important factor in criteria tree model and most suitable districts for channel terracing implementation was selected. Area for banquette with first priority had 278 ha that is showed in final map.