Flood Disaster Risk Assessment Of Lijiang River Basin Based On SWAT Model

This study aimed to evaluate the flood risk in the Li River Basin and provide scientific basis for flood control planning and engineering in the area.The trends,breakpoints,and periodicity of runoff,precipitation,and temperature in the Li River Basin were diagnosed to establish the correlation between runoff and its influencing factors.An ArcSWAT model was constructed using elements such as basin boundaries,hydrological stations,terrain,land use,and soil types,and was used to simulate the runoff in the Li River Basin,with the parameter ranges of the model established.Finally,an flood risk assessment model for the Li River Basin was built using the AHP hierarchical analysis method and disaster risk assessment theory,combined with GIS platform.The main conclusions are as follows:(1)The runoff in the upper reaches of the Li River showed a gradual decreasing trend.After a comprehensive analysis of human activities and climate change,it was found that the significant change in Li River runoff in 2018 was caused by a combination of factors such as changes in land use,construction of flood control and water supplement projects,and climate change.(2)In the Li River Basin,temperature is negatively correlated with runoff and positively correlated with precipitation.In addition,this study focused on analyzing the correlation between temperature,precipitation,and runoff,and found that temperature has a greater impact on runoff than precipitation.(3)The ArcSWAT model was constructed and calibrated,and the 5 parameters that had a significant impact on runoff simulation in the study area were soil bulk density(SOL＿BD),groundwater delay time(GW＿DELAY),base flow water level threshold(GWQMN),deep aquifer seepage fraction(RCHRG＿DP),and main channel Manning coefficient(CH＿N2).(4)Through the verification of the correlation coefficient R~2 and the Nash efficiency coefficient,it was found that the ArcSWAT model can accurately reproduce the actual runoff changes in the upper reaches of the Li River.This proves that the model has good adaptability in simulating the runoff process in the upper reaches of the Li River,and meets the requirements of model simulation.(5)The stability level of the disaster-prone environment in the Li River Basin shows a trend of gradually decreasing from the surrounding mountain areas to the plain.The vulnerability level of the disaster-bearing body in the Li River Basin is generally low,and the areas with high vulnerability levels are mainly distributed in the urban area of Guilin city.(6)The area with high and relatively high flood risk in the Li River Basin is1341.61 km~2,accounting for 9.11%of the total study area,and mainly concentrated in the northern part of the study area.The research results provide scientific basis for flood control planning and engineering in the region,and propose a series of feasible flood control measures and suggestions,including strengthening flood control engineering construction,rational land use planning,and improving the flood warning system,to minimize flood losses in the Li River Basin and provide reference for flood risk assessment in other areas.