Analysis of debris flow engineering treatment effect based on DEM data preprocessing in small watershed: A case study of Fangjiagou debris flow, Zhangxian County

After the Minxian-Zhangxian magnitude 6.6 earthquake on July 22, 2013, debris flow occurred in Fangjiagou, Zhangxian County. To reduce the potential damage of debris flow, a three-level check dam and drainage channel were built in the gully to regulate the peak flow of debris flow and reduce the threat to the downstream accumulation fan protection objects. However, The control project currently in place in the study area has been designed based on the characteristics of previous debris flow occurrences, and its effectiveness for future incidents remains to be tested. This study used the bilinear interpolation method to fine process DEM data of high-precision remote sensing image, reconstructed the check dam and topographic model of Fangjiagou small watershed, and adopted FLO-2D software to simulate and analyze the movement characteristics and risk of Fangjiagou debris flow under different precipitation probability conditions; the effect of debris flow control project thus then was evaluated. The results show that: As the intensity of rainfall gradually increases, the desilting ability of the barrier dam for debris flow increases gradually, and the debris flow does not pass the barrier dam. The limiting efficiency of flow rate of debris flow is 80.1%, which greatly weakens the impact of failure ability of debris flow. The area with a high risk of debris flow is reduced by 45.34%, which effectively reduces the influence range of debris flow. This study presents that the debris flow blocking project has a remarkable treatment effect under the simulation condition of Fangjiagou dam construction, which can provide effective guidance for the feasibility test of debris flow blocking projects in similar small watersheds.