Hazard assessment of debris flow induced by short-time heavy rainfall based on RAMMS numerical simulation

Abstract

Objective Debris flows caused by short-term heavy rainfall are a frequent occurrence in Zhejiang Province and pose a serious threat to the lives and property of mountain residents. Therefore, the assessment of debris flow risk has significant theoretical and practical value for disaster management in the province. To investigate the hazard of debris flows caused by short-term heavy rainfall, the Wushankeng watershed was selected for research by means of field investigations and remote sensing interpretations, combined with numerical simulation. Methods The obtained results revealed the geological environment, development characteristics and disaster chain formation mechanism of debris flow in the watershed. The RAMMS numerical simulation software was used to simulate the debris flow depth and the velocity under different rainfall frequencies, and the hazard assessment was carried out based on these movement characteristics. Results The results of the research indicated that loose rock and soil at steep slopes experienced shallow landslides under the effect of short-term heavy rainfall. Then, under the control of the slope and gully topography, it migrated to the mouth of the gully, and during the movement, the scale of the debris flow was expanded by erosion. Finally, it was deposited in the wide and gentle accumulation area. As the intensity of the study area rainfall increased to a 50-year or 100-year occurrence, the scale of the debris flow increased, but it was limited by the gentle topographical conditions of the accumulation area, and it was unable to effectively discharge at the mouth of the gully. However, the indicators of mud depth and flow velocity in the resident areas upstream of the accumulation fan significantly increased, and the area of high-intensity areas in the accumulation area increased from 7 276 m2 to 12 660 m2. Combined with the results of debris flow activity analysis, the combination of rainfall monitoring in the formation area, constructing rigid, flexible, or slit check dams in the circulation area of the main channel, and setting up drainage channels in the accumulation area can effectively protect the lives and properties of residents. Conclusion The research results can provide reference for debris flow hazard assessment and engineering treatment in the study area and Zhejiang Province.

Keywords

• short-time heavy rainfall
• debris flow
• disaster chain
• ramms
• hazard assessment