Risk Assessment of the Chaancun Debris Flow Gully and Mitigative Measures in Dalian City, China

The Chaancun debris flow gully is located on the mountain slope of the crown of the Chaancun landslide. The hiking corridor, leisure square, Lvshun middle road, and Wangjiadian reservoir are situated below the debris flow track. The Chaancun debris flow gully poses a serious threat to the safety of this site and to the development of tourist attractions. First, an appropriate recognition of the debris flow gully is required by a field investigation. This gully is steep and straight. The weathered and denuded rocks coming from the fault zone are the debris source. In addition, concentrated rainfall occurs in this area. Therefore, the debris flow gully has the forming conditions of a debris flow. Many factors affect the formation and assessment of a debris flow, and they result in uncertainty, randomness, and fuzziness. Therefore, the fuzzy mathematics method is suitable for the risk assessment of debris flow. To improve the reliability of the risk assessment of the Chaancun debris flow gully, primary fuzzy assessment and secondary fuzzy assessment considering hierarchical analysis were undertaken for quantitative risk assessment. This gully was categorized as "extremely hazardous;" thus, appropriate mitigations such as building a concrete dam and planting in bare areas were designed and implemented.