Research On Risk Assessment Of Rainfall Induced Disaster In Mountain Area Of Sichuan Province

Since the 21st century,due to the effects of climate warming,natural disasters caused by extreme weather around the world have occurred frequently,causing huge casualties and property losses.China is a mountainous country.Risk assessment of disasters caused by rainfall in mountainous cities can effectively provide relevant departments with scientific basis for disaster prevention and effective disaster avoidance guidance.For the risk assessment of debris flow and flood disasters in Ya'an City,the local natural geographical environment and socio-economic conditions are first considered,and different types of evaluation index factors are selected from the aspects of hydrology and meteorology,topography,geology and society.After extracting various types of data through tools such as GIS software and MATLAB,the dimension is eliminated through formulas and standardized processing is performed.Build a three-layer neural network model,and input various types of data after standardization into the neural network model as input layers.The self-training of the neural network can effectively eliminate the interference of human factors.In the process of continuous feedback correction,the training is completed and the weights of various index factors are output.Multiply various index factors by their respective weights,and then use GIS software to superimpose,and finally get the risk distribution map of debris flow and flood disasters in Ya'an City.For the research on the vulnerability of flood disasters in Bazhong City,this article is based on the emergy theory from the perspective of ecology.Considering the three aspects of Bazhong City's hydrology and water resources environment,land use types and social factors.Several evaluation indicators were selected,such as rainfall runoff data,the number of medical staff and students,total social fixed investment and GDP data,and main land use type data.Based on the solar emergy value,the emergy value contained in various data is calculated by the emergy value conversion rate formula.According to the calculation formula,the emergy values contained in various types of data are superimposed to calculate the exposure,sensitivity,and adaptability of various districts and counties in Bazhong City when they are flooded.Based on the three,the potential impact index and vulnerability index are calculated.Finally,through GIS software,the potential impact and vulnerability zoning maps of each district and county were made to complete the vulnerability assessment of flood disasters in Bazhong City.The main conclusions of this paper are as follows:(1)The high-risk areas of debris flow hazards in Ya'an City are mainly concentrated in Hanyuan County,Yucheng District and Mingshan District.The reason is that most of these areas are distributed on the fault zone,the terrain slope is large and the population is dense,so when the debris flow occurs,it is easy to suffer more serious losses.The three administrative districts of Lushan County,Shimian County and Yingjing County belong to areas with moderate risk of debris flow.The overall risk of debris flow disasters in Tianquan County and Baoxing County is the lowest,because most of these areas have good vegetation coverage and sparse personnel,but disaster prevention work needs to be done to prevent the occurrence of debris flow disasters.(2)The high-risk areas of flood disasters in Ya'an City are mainly concentrated in the three administrative areas of Mingshan District,Lushan County and Yucheng District.The reason is that these areas are lower in altitude,located in the middle reaches of the Qingyi River Basin,with heavy rainfall and developed water systems,so they are more prone to flood disasters.Tianquan County,Yingjing County and Baoxing County belong to the medium risk area of flood disaster.Most of the areas in Hanyuan County and Shimian County are in high mountain areas and belong to the Dadu River Basin.The rainfall is relatively small,so the risk of flood disasters is the lowest.(3)By analyzing the distribution map of debris flow disaster risk and flood disaster risk map in Ya'an City,it can be found that some areas of the three administrative regions of Lushan County,Yucheng District and Mingshan District are at the same time in high-risk areas of debris flow disaster and flood disaster.These areas need special strengthening of disaster prevention and relief work.(4)The region with the greatest potential for flood disasters in Bazhong City is Tongjiang County.The reason is that the economic development in this area is slow,and there are relatively few medical personnel,so it is easy to be greatly affected in case of flood disaster.Pingchang county and Bazhou District are relatively less affected by flood disaster,and Nanjiang county is the least affected by flood disaster.Because Tongjiang County has more residential land and industrial and mining land,its vulnerability is higher.The vulnerability of Pingchang county and Nanjiang county is relatively low,and that of Bazhou District is the lowest.