Quantification of qualitative geomorphology method for water erosion estimation (Case Study: Three sub-watersheds of Latian Dam basin)

Soil erosion by water is considered as one of the major threats for sustainable land management. In Iran, soil erosion studies has begun since 40 years ago, but there is no native model to evaluate soil erosion yet. This research is the first attempt to develop a new erosion model, based on the fuzzy logic approach. The study is took place in Latian Dam basin, Iran. Using GI Systems some effective factors on soil erosion including geomorphologic, lithology, topographic, climatic, hydrologic, vegetation, land use and soil properties factors that contain 81 indices, were analyzed using correlation matrix, cluster analysis and Kruskal-Wallis test. The effects of 19 factors were significant which used to develop conceptual model. To quantify conceptual model, a fuzzy modeling approach was used. Seven fuzzy operators were used within a GI System for determining erosion hazard. The results show that the erosion map derived from fuzzy Gamma operator (?=0.8), has the best prediction of soil erosion hazard over the study area and its overall accuracy is up to 92%. Predicting the amount of specific sediment yield of the 3 sub-watersheds of the study area was done using multivariate regression analysis with stepwise method using a data set of eight input parameters. The results indicated that the equation that included variables of erosion coefficient and area of sub-watershed stated adjusted square correlation coefficients (R2adj=99.09%). The results suggest that fuzzy approach is very useful to predict soil erosion and sediment yield over the study area.