Evaluating the Erosion and Deposition Rates and the Role of Geomorphological Indices in Mighan Watershed

Soil erosion is one of the most important factors annually threatening a vast part of Iran’s lands and downgrades or completely destroys the quality of the agricultural lands and rangelands. In regions wherein the tectonic movements are active, the deformations resulting from soil erosion stirs responses in the drainage network. The present study tries investigating the soil erosion and deposition proneness and neotectonic activities through geomorphological indices of Mighan Watershed situated in the northeastern side of Markazi Province. The study is a descriptive-analytical research that is conducted based on field investigation, library research and statistical evaluations in such a manner that various models are made to investigate the erosion and tectonic characteristics of the region. The results indicated that the lowest erosion and deposition rates in the sub-basin 6 are 104.3 t/km² and 20.5t/ km² per year and the highest erosion and deposition rates belong to sub-basin 10 with values equal to 148.7t/ km² and 27t/ km² per year, respectively. Corresponding to the results, the increase in BS morphological index causes an increase in the erosion and deposition rates but an inverse relationship was documented between geomorphological indices and AF, T, S and Sl. In between, SL index was found playing a more accentuated role in the creation of erosion differences between sub-basins. In sum, the study results indicated that the deposition and erosion potentials of the studied basins in Mighan Watershed are variable and a collection of geomorphological factors are effective in this regard. It can be stated according to the results of correlation analysis between geomorphological indices and erosion and deposition values that the increase in BS (basin shape) index brings about an increase in the erosion and deposition rates. The results of multivariate regressions, as well, demonstrated that besides the inverse association between AF (asymmetry of the drainage basin) and erosion, there is a positive relationship between BS and erosion and deposition.