Document Type : Research Paper
Authors
1 Natural Resources Engineering Department Yasouj University
2 Graduated M.Sc., Rangeland and Watershed Management Department, Faculty of Natural Resources, Khatam Al Anbia Behbahan University of Technology, Behbahan, Iran
3 Assistant professor Behbahan Khatam Alanbia University of Technology
Abstract
Check dams have the largest amount of watershed improvement operations in Iran. Therefore, considering the frequency of construction and as a result the cost of construction, it is necessary to investigate their performance in watersheds to identify their strengths and weaknesses. In this research, the evaluation of the placement of check dams has been investigated from the perspective of sedimentation performance in the Nehzatabad watershed in Kohgiluyeh county. For this purpose, after determining the parameters related to the volume of sediments deposited behind 11 selected check dams and calculating their volume, the amount of sediment yield was first measured and then estimated by calculating three different sediment trapping coefficients. Finally, by calculating the sediment delivery ratio, the measured and estimated sediment yield was converted into its equivalent soil loss on the surface in the upstream sub-watershed of the check dams.The results showed that the amount of specific sediment yield measured in check dams is from 0.001 to 1.08 and on average 0.13 tons per hectare per year. Considering the ratio of sediment delivery, which varied from 18 to 51 percent for selected dams, this amount of sediment yield is equivalent to 0.01 to 2.1 and an average of 0.3 tons per hectare per year of soil loss in the upstream sub-watersheds of check dams, which is a very small number compared to the figures presented for the average soil loss in most of Iran's watersheds. Taking into account different coefficients of sediment trapping, the estimated average values for sediment yield in check dams are 2.88, 7.46 and 0.87 tons per hectare per year which are equivalent to 9.41, 30.5, 3.49 tons per hectare per year of soil loss respectively, which compared to the average amount of soil erosion in Iran's watersheds, seem more reasonable and logical numbers.
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