Risk Assessment Of The Disrupted Flood Disaster Chain

Based on DB-IWHR dam flood analysis program and the Massflow numerical simulation software,in order to "6.17 danba debris flow" event in the formation of the Mellon lake as the research object,calculated the dyke flow process,the one-dimensional flood routing calculation,get the characteristic values of characteristic sections of flooding downstream using 2 d flood routing computation,get flood scope,Finally,the risk assessment of dam-break flood in the downstream area is carried out according to the inundation range obtained by evolution.The main research contents and results are as follows:1.Calculate the rupture flow process based on DB-IWHR program.Different outburst water levels were selected and five different schemes were formulated.The outburst flow process curves under different schemes were obtained by calculation.The lowest outburst water level is 100m,the peak flow is 1974.02m3/s,and the peak arrival time is 1.60 h.The highest outburst water level was 2160m,the peak discharge was4107.53m3/s,and the peak arrival time was 2.15 h.Compared with several schemes,the higher the water level is,the greater the peak discharge is.2.The sensitivity of DB-IWHR was discussed.Taking scheme 2 in this case as a comparison scheme,sensitivity analysis is carried out on inun DATION coefficient M,start-up velocity Vc,erosion coefficient A and erosion coefficient B.The results show that in this case,the effect of the submergence coefficient m on the peak discharge fluctuates greatly.The initial velocity Vc has little effect on the peak discharge.There is a limit value for the influence degree of erosion coefficient A,and the influence is small within the limit value,while the peak discharge fluctuates greatly outside the limit value.The effect of erosion coefficient B on the peak flow rate is relatively large.3.To collapse flow process curve of the inlet boundary condition,the calculation of one dimensional flood routing in the downstream area from mizoguchi Mellon to danba county set up six sections,the most distant distance of 17.8 km,at each scheme under the peak flow attenuation rate was 0.11%,the biggest with the increase of evolutionary distance,each scheme under flow along the Cheng Hongfeng gradually reduced.4.Three schemes were selected to simulate and analyze the evolution process of outburst flood with Massflow software,so as to obtain the submerged range of the downstream urban section from Meilonggou to Danba County and the change of flow depth and velocity during the evolution process.The results show that the inundation range of the three schemes is roughly the same.It has passed the first village of A ’Niang Gou in 20 min and reached the vicinity of Lilong Village in 150min.The flow depth and velocity along the path experienced a process of slowly increasing to the peak value and then rapidly decreasing to a stable value,in which the flow depth was up to 13m and the flow velocity was up to 12m/s.5.According to the two-dimensional evolution results,the maximum flow depth,maximum flow velocity and maximum erosion depth are taken as risk indicators,and the population density,GDP and land use type of the study area are taken as vulnerability indicators to conduct risk assessment for the downstream urban section from Meilong Goukou to Danba County.Results The risk levels in the study area were mainly low,medium and high,among which the low risk area accounted for 79.99%,the medium risk area 18.54%,the high risk area 0.47% and the very high risk area was 0.6.According to the simulation results of this thesis,the flood area did not reach the Danba County,but the distance was relatively close.For safety reasons,emergency measures should be taken to the Danba County in the first time after the Meilong quake lake burst.