The Difference Of Space-time Characteristics And Flood Responses Of Typhoon And Non-typhoon Rainstorms In Typical Coastal Basin Of Southeast China

As a common meteorological disaster,rainstorms and floods have a wide range of influences,which can easily cause huge economic,property losses and many casualties.Fujian Province is located in the southeast coastal area of China,the economy is developed.The landform is mainly mountainous and hilly,the river basin area is small,the storage capacity is poor,and the summer rainstorms are frequent,which is easy to cause flood disaster.According to the different causes of rainstorms,the rainstorms in Fujian Province can be divided into typhoon rainstorms caused by tropical cyclones such as typhoons and all kinds of non-typhoon rainstorms except typhoon rainstorms.Further study on the temporal and spatial characteristics of typhoon rainstorms and non-typhoon rainstorms and their flood response can refine the regional rainstorms flood law,reveal the flood response mechanism of rainstorms in different weather systems,provide new ideas for the study of rainstorms flood in southeast coastal areas,and provide scientific and technological support for regional flood control and disaster reduction.Based on the analysis of typhoon and non-typhoon rainstorms and their flood events,this study is based on two aspects :(1)based on the data of the largest flood in Jinjiang Basin of Fujian Province from 1964 to 2014 and the relevant data of typhoon,a series of rainstorm characteristic indexes are selected to analyze the temporal and spatial characteristics and differences between typhoon rainstorm and non-typhoon rainstorm in Jinjiang Basin;(2)Based on the data of 53 rainstorms and floods from1996 to 2018 in Shanmei Reservoir catchment area of Fujian Province,the HEC-HMS model is used to determine the classification rate of typhoon rainstorm and non-typhoon rainstorm,and the different rules and mechanisms of flood response between typhoon rainstorm and non-typhoon rainstorm are revealed by analyzing the difference of parameter rate of two kinds of flood models.The results show that(1)the temporal and spatial characteristics of typhoon rainstorm and non-typhoon rainstorm are obviously different.From the time variation characteristics,typhoon rainstorm duration is short and the fluctuation is obvious,non-typhoon rainstorm duration is opposite,and non-typhoon rainstorm time distribution is more uneven.In terms of spatial variation characteristics,the spatial distribution of non-typhoon rainstorms is more uniform,and the typhoon rainstorms are concentrated in the southwest coastal area of the basin,and the terrain uplift intensifies the uneven spatial distribution of typhoon rainstorms.(2)Flood classification modeling improves the accuracy of the HEC-HMS model used in regional rainstorm flood simulation.Respectively according to the calibration results build the model at the beginning of the sensitive parameters loss rate rises(lambda)and flow rate and velocity(V)and maximum 3 hours,the experience of the surface rainfall intensity relationship,according to the flood classification can significantly improve the empirical relationship between the fitting accuracy(P < 0.05),increase the model accuracy,effectively reduce the simulation error model,the better the results.(3)There are significant differences in flood response between typhoon and non-typhoon rainstorms.By comparing and analyzing the flood characteristic factors such as peak discharge,flood volume and flood duration of typhoon and non-typhoon rainstorm floods,and the changes of the initial loss rate(?)and wave velocity(V)of two sensitive parameters of model rate,it is shown that the flood response of typhoon and non-typhoon rainstorm is obviously different.Typhoon rainstorm is characterized by higher rainfall intensity and lower soil moisture content on the underlying surface in the early stage of the rainstorm,which results in smaller initial flood discharge,larger peak flood discharge and flood volume,shorter flood duration,and steep rise and fall.The initial loss rate(?)and wave velocity(V)of the model parameters of typhoon rainstorm flood are also larger..