Prioritization the critical sub-watersheds based on soil erosion and sediment using Watershed Erosion Response Model (WERM) and morphometric analysis (Case study: Rozechai watershed, West Azerbaijan Province)

Prioritization of critical sub-watershed is an important procedure to control runoff and erosion phenomenon and considered as effective way in management of watersheds and achieving sustainable development. The main aim of this study is assessing the soil erosion-prone areas and prioritization of 30 hydrologic response unit of Rozehchai Watershed that located in West Azerbaijan province (186.41 km2) using Morphometric Analysis and Watershed Erosion Response Model (WERM). The WERM index has been calculated using landuse, slope, and rainfall maps. The sub-watershed-related morphometric indices were used under the two categories of linear and shape parameters (e.g. Stream length, Drainage density, Length of overland flow, Form factor, Circularity coefficient, Elongation coefficient and Compactness coefficient). The priorities of sub-watersheds with respect to erosion rate were determined using the values of WERM model and the total mean of morphometric parameters values. Finally, the integrated map was obtained according to the highest values of calculated indices and the critical condition of each sub-watershed was determined based on the final values of assigned scores. The results showed that the SUB6, SUB2, IB11, IB3 and IB10 sub-watersheds had critical condition and are ranked as high priority areas, respectively. These areas require immediate practical and the control and protection. In addition, the used method based on watershed response and sensitivity to soil erosion can be used as effective tools in prioritization of watershed for implementation of soil erosion control measures. In this regard, defined critical sub-watersheds based on topographic and morphometric indices along with natural and anthropogenic factors can be considered in the planning of soil erosion control in watersheds and soil and water conservation programs.