Appropriate Method of Determination the Sediment Retained by Check Dams in Arid Region (South Eastern Iran)
Abstract
Mansour Jahantigh and Moien Jahantigh
Check dams as an important engineering structure are widely used to modify the hydrological responses and reduce soil erosion in watersheds. Hence, to identify the effectiveness of check dams and gain better insight into the construction of this structure in arid areas, it is necessary to present the adapted method to calculate the sediment volume trapped by check dam system. In this study, we evaluate three methods to calculate and estimate the sediment volume trapped by check dam systems based on geometric shapes including U-shaped geometric, Prism, and Pyramid. These methods were tested on a sample of 25 check dams that were constructed in the Snib basin (southeast Iran). by topographical survey and applying technical field works, the dimensions of the sediment deposited behind of each check dam were measured and the volume of retained sediment, Trap efficiency, sediment yield, total sediment yield and sediment emission was calculated for each check dams. The results showed that absolute variation in the volume of retained sediment and sediment yield based on the U-shaped method comparing other methods is from 23% to 34%. Meanwhile, due to the high variability of the check dam, comparing methods in groups combined present significant differences in sediment volumes, sediment yield, and total sediment yield when check dams are between 15 - 35 m in length and have a height of between 2 and 4 m. Overall, the use of U-shaped geometric method with high accuracy can provide valuable information to estimate total sediment yield and evaluate check dam effects when valleys present a uniform U-shape such as our study area. The outcome of these studies can be used as a basis for evaluating the effects of check dams to estimate sediment yields and mitigate natural hazards at ungauged basins in arid areas.