Comparatives investigation of useful life and hazard risk based on return period watershed projects with AHP approaches Case studyKhorasan Razavi basins

One of the major issues in the construction of drainage structures should be protected in proportion with the river type. The design flow is based on the useful life period and also takes risks plays a very important role in selecting the location and type of structures and its design, ultimately. In this study, the spatial distribution of watershed management structures based on river order in 13 the study watershed is located in the province of Khorasan. Results expressed that in useful 5 year, With an acceptable hazard risk of 25% for straw dam and Rocky dam structures, in useful 10 year with hazard risk of 20% for the gabion, in useful 15 year with hazard risk of 15% for the cement dams and in useful 20 year with hazard risk of 10% for earth dams Based on the analytic hierarchy process had the highest scores. While The rate of return on plan acceptable straw dam structures Rocky dam and gabion structure to the 2x and for cement dams and earth dams 4x values is also used in the design is¬ implemented.