Assessing the Effects of Watershed Management Projects in Flood Decreasing in Gawdarreh Catchment, Kurdistan, Iran

Major part of Iran is located within the arid and semi-arid area. Small amounts of rainfall with inadequate distribution of it caused droughts and water shortages in such areas. Supply clear water is the main basis for sustainable use of natural resources. Preservation of national resources by reducing water losses and consequently enhances the vegetation in the catchment areas are the main goals of the watershed management operations. Watershed projects in various stages are being implemented in the watersheds in Iran by different administrative units. The evaluation of watershed operations performance, to find strengths and weaknesses of administration actions and their effectiveness, in order to achieve better management strategies and implementation plans, is inevitable in watershed management. This study conducted to evaluate the effect of watershed operations on flood control in the Gawdarreh watershed in Kurdistan, Iran. The watershed area was 6.27 km2 which is a subbasin of Gheshlagh watershed in Sanandaj. Basic information and required data such as rainfall and runoff data, were gathered from existing reports and maps and related organization. The locations and characteristics of executed operations were recorded by field observations. To compare the behavior of watershed, before and after implementation of operations, hydrological model, HEC-HMS, were calibrated and validated using observed rainfall and runoff events. The impacts of implemented operations on increasing runoff storage capacity and consequently reducing the flood and changing the output flood characteristics were analyzed and evaluated. The results show that despite flaws in the implementation of watershed management operations, the volume of stored runoff increased and peak streamflow is reduced. Results indicate a positive effect of applied managements that alter the watershed behavior in order to reduce flooding.