Evaluating Group Efficiency of Check Dams Using Analytical Hierarchy Process (AHP)

Structural operations in watersheds, particularly check dams cost a lot. Therefore, it is important to evaluate their performance. To evaluate the performance of any project, one needs some indicators that can evaluate the overall performance of the project by assessing them. For evaluating of check dam's efficiency, one should evaluate in detail the influencing indicators. Indicators based on behavior of the nature and the efficiency of implemented measures. The purpose of this research is providing scientific and precise criteria for assessing overall efficiency of check dams and evaluating some series of check dams in Chaharmahal and Bkhtiary streams using these criteria. In this work, 12 streams are selected with Gabions and Stone- mortar check dams that are in operation within 1986-2011 and have the most diversity in design, dimensions and catchment conditions. Then, seven Criteria defined that affect group efficiency of check dams or relate to entire network like; spacing of check dams based on compensation gradient, type of check dam, use of existing material, minimal destruction in the site, fixed elevation of channel, coordination of reservoir volume with sediment deposited, and minimal flooded areas. The score of any item in these criteria computed based on introduced formulas. Then, all criteria weighted with paired comparisons questionnaire method. Finally using an optimized model in analytical hierarchy process, all understudy check dams were assessed. Results showed that the criterion" spacing check dams based on compensation gradient" was 0.297, and "type of check dam" was 0.168, have the most effect on group efficiency of check dams. Also, between studied waterways, series of check dams in "Marghmalek" and "Sorkhkooh" despite of their simplicity and being small get the highest scores (80 %) and in fact had the best performance.