Research On Risk Assessment Technology Of Torrential Flash Floods Disaster In Henan Province

Based on the fusion precipitation data and the daily and hourly precipitation data from 111 meteorological stations in Henan Province,this paper analyzes the precipitation variation in the upper reaches of Luohe River in Henan Province.The research bases on a two-dimension hydrodynamic model of Flood Area,and uses a typical small watershed in the upper reaches of Luohe River in Henan Province as object of study.A detailed diurnal variation law of rainstorm is adopted to simulate the risk of rainstorm mountain flood disaster.Combining with the information of disaster bearing body,the scenario assessment and dynamic assessment of rainstorm mountain flood disaster are realized.The results are as follows:（1）The summer precipitation in Henan Province showes the overall characteristics of low in the middle and north（north of 34°N）,high in the southwest and south（south of 34°N）;The spatial distribution characteristics of summer precipitation are mainly affected by precipitation frequency,which has a strong consistency with the spatial distribution of precipitation frequency,and the spatial correlation coefficient between the two is as high as 0.754（n=1606,P<0.01）;The relationship between summer precipitation,precipitation frequency and precipitation intensity and longitude,latitude and altitude is significant.The contribution of short-term and long-term summer precipitation to the total precipitation in Henan Province are 46.04%and 53.96%,respectively,and the contribution of long-term summer precipitation to the total precipitation is the largest.（2）During 1961-2018,the annual mean rainstorm days in Henan province shows a significant upward trend,with a rate of 0.34 d·（10a）^-1.94.6%of meteorological stations in the province have a positive climatic tendency for the annual mean rainstorm days,and the significantly increased number of stations accounted for73.0%of the total number of stations.The mean rainstorm days per year is 1.4 d.July has the most rainstorm days,with a mean of 0.52 d,accounting for 37.1%of the annual mean rainstorm days.During 1961-2018,the diurnal variation of the rainstorm total precipitation in Henan Province presents a single-peak structure,with the main peak value appearing at 5:00,which is 4.5 mm.The diurnal variation peak of rainstorm shows a fluctuating downward trend,with a rate of 0.16 mm·（10a）^-1.Most of the diurnal variation peaks occurs between 00:00 and 08:00,which has 42 years,accounting for 79.3%of total years.From the perspective of spatial distribution,the diurnal variation peaks of rainstorm in meteorological stations occurs between 00:00and 06:00,accounting for 73.5%of the total meteorological stations.During2014-2018,the agreement of hourly and daily precipitation dataset in Henan Province is 100%.The main and secondary peak value of anastomotic rainstorm appears at4:00 and 17:00,4.3 mm and 3.4 mm respectively.Most of the peak of the diurnal variation occurs between 13:00 and 18:00,accounting for 33.9%of the total stations.The rainstorm days and rainstorm diurnal variation are affected by hourly and daily dataset.The main performance is the annual mean rainstorm days and its variation trend are not consistent and also the difference of the rainstorm diurnal variation.（3）The optimal fitting function in the daily precipitation recurrence period of Luoshi station is Gen.Logistic function.The daily precipitation of once every 100 a,50 a,20 a,10 a and 5 a in the upper reaches of Luohe River are 116.7 mm,103.9 mm,88.8 mm,78.3 mm and 68 mm,respectively.Taking daily precipitation scenario of once every 100 a as an example,the risk of mountain torrent disaster in the upper reaches of Luohe river is higher in the middle and higher in the south than in the north.The high risk areas are mainly concentrated near Chengguan town and the two sides along the Yiluo River.The high-risk area is 92.0 km²,accounting for 17.37%of the total GDP and 8.88%of the total population.It also includes 23 residential areas,12 petrol stations,31 schools and 31 medical service points.The submerged water depth above 0.6 m was 110.3 km²,and the remaining recurrence periods are 103.4km²,95.1 km²,89.6 km²and 82.8 km²,respectively.