Morphotectonic of Tang-e-sarhe Catchment and its Effect on Morphology and Behavior of the River, Nikshahr, Southeast of Iran

The catchment of Tang-e-Sarhe river is located about 60 km northwest of Nikshahr in southern Sistan and Baluchistan Province in Southeast of Iran. This study aims to evaluate the active tectonic of the area using geomorphic indices. The research instruments include Landsat satellite images, digital, topographical and geological maps of the area and Arc GIS software. Tang-e-Sarhe is divided into two distinct sub-basins and the active tectonic parameters of the catchment including hypsometric integration, asymmetry factor, transverse topographic asymmetry factor, Mountain-Front Sinuosity and ratio of valley-floor to valley height are determined. Moreover, the changes in the river bed and its pattern are also investigated. Thus, cross-sections for waterways was calculated and their positions were recorded using GPS and then, transferred to the maps. Curvature coefficient index indicated that river meander, as a result of high tectonic activities in this area, a decrease in bed erosion and an increase in the erosion of the sides, tends to develop in upstream direction. According to Pit's tortuosity coefficient table, the tortuosity coefficient of Tang-e-Sarhe River is 1.24, showing a sinuosity. Indices also reveal that sub-basin (1) is among the most active catchments regarding the tectonic activities while, subbasin (2) shows less activity than sub-basin (1) and is relatively active. Also, the tectonic activities are decreased from north to south.