The assessment of hydrologic performance of check dams on flood control in Kan River basin

A check dam is a small dam with a simple and low cost structure and because of its specific material and simple building technology, it has a wide range of applications in flood control projects. In this research, the effects of check dams on reducing the flood peak and increasing the time of flood flow to reach to peak were investigated for Kan basin in north-west of Tehran. The hydraulic and hydrologic situation of the Kan basin was modeled using HEC-HMS software. Using hydrologic modeling the effect of building check dams on flood characteristics was studied in three scenarios of river slope change. The results showed that check dams reduced the flood peak to reduce between 0 and 0.9% in the first scenario (0.5 of the natural slope) and from 0.4% to 3.5% and 3.9% to 10.6% in the second (0.1 of the natural slope) and third (0.01 of the natural slope) scenarios, respectively. The time to peak also increased from 10 to 50 minutes. In hydraulic-hydrologic modeling, the effect of constructing check dams with no sediment in their reservoir was investigated for rainfalls of different return periods. The results revealed that with increase in rainfall return period, the effect of check dams on reducing flood characteristics will decrease. For instance, in the case of 100 check dams, the percentage reduction in peak outflow will decrease from 22.8 to 1.2 % for rainfalls of 2 and 20 years return period, respectively. In general, construction of check dams has no considerable influence on reducing constructive effects of floods. In other words, check dams should be used together with other structural and non-structural flood control methods.