Evaluation of the Most Appropriate Time Basis of Rain Intensity in Determinationof Storm Suspended Sediment

Accelerated soil erosion and resultant sediment yield from catchments are key obstacles in reaching sustainable development. Hence، the evaluation of effective factors on erosion and sediment yield processes is considered as a prerequisite in proper watershed management. The erosive force of rain causes soil degradation، decreases surface permeability and then increases surface runoff، implying that rain plays the greatest role in water erosion. Different indices representing the rain erosivity factor have been proposed among which the EI30 index is considered as one the most important one with global application. However، researches have shown that I30 then is associated with efficient accuracy in all areas. Therefore، it is necessary that the most effective time basis for rain intensity is determined for any combination of physical and natural conditions in watersheds. In this regard، the present research is conducted in Chehelgazi Watershed of Gheshlagh Dam in Kurdistan Province for the purpose of determining the most effective time basis of rain intensity in storm sediment. The results of this research indicated that this index multiplying the kinetic energy in the rain intensity in the time basis of 20 min (EI20)، has the highest correlation (r=0. 810) with storm sediment yield.