An assessment framework for the mitigation effects of check dams on debris flow

Debris flow can be very destructive, especially in areas of dense population on mountain foothills. Check dams are constructed across drainage channels and are beneficial for reducing flow velocity and soil erosion, as well as controlling debris flows. On July 26,1987, a destructive debris flow occurred in a watershed north of Tehran, Iran. A series of check dams were constructed in the watershed to mitigate the hazards of future debris flow due to the importance of the region. This study first proposes a procedure to estimate the volume of the sedirnents in a debris flow from the calculated volume of an equivalent regular flood. The procedure to estimate the sediments volume is employed in a framework to assess the effects of constructed check dams for a similar debris flow in the region. The framework Considers the unfilled storage of the check dams for estimating the volume of the sediments in each catchment. Field measurements were implemented to estimate the available storage of check dams. The volume of sediments in two cases was estimated: 1) the debris flow in 1987 and 2) a probable debris flow at current time considering the available storage of constructed check dams. The comparison shows that the volume of sediments reaching the outlet of the watershed decreased 13% as the effect of check dams in trapping sediments. Applying the proposed framework to this case study shows its ability in assessment of check dams' impact on debris flow.