Abstract:

Luan city is situated on the north slope of Dabie Mountain.As a subtropical monsoon climate zone,the spatial and temporal variation of precipitation is obvious in this city.It suffers from heavy rainstorm and flood disaster frequently especially in the flood season.Analysis on rainstorm flood risk is of great importance for taking precautions and fighting against flood disasters in Luan city.According to the principles of risk assessment for natural disasters,an assessment model on Luan rainstorm flood risk was built including 4 factors：the risk of disaster causing,the sensitivity of disaster environment,the vulnerability of disasterbearing bodies and the ability of disaster prevention/reduction.Main data used in the research includes  daily precipitation data from 6 meteorological stations in Luan city from 1956 to 2011,DEM in 30 m resolution,spatial distribution maps of the water systems and lakes of the research area.Besides this,we also make use of total acreage,population,GDP as well as the acreage under cultivation of villages and towns in Luan city.With the support of ArcGIS10.0,using 30 m×30 m raster as basic assessment unit,we ranked each influencing factor according to the mean and standard deviation and then defined affecting degree for each grade.The map of rainstorm flood disaster risk division in Luan city was created ultimately by overlaying raster coverage of the influencing factors,and the weights of which were determined through the Analytic Hierarchy Process (AHP).Results show that the rainstorm flood risk in the southwest is in general different from that in the northeast.Although the annual precipitation is abundant and heavy rainstorm occurs frequently in the southwest,the rainstorm flood risk in this area is lower than that in the northeast because of its low population density and low per capita GDP resulted from mountain area of high altitude.The highest possibility of flood risk is found in Luan and Shouxian town.On shores of rivers and lakes as well as depressions,the rainstorm flood risk is relatively high.Using the flood disaster during summer in 1991 to test and verity,the evaluation solution is consistent with the actual situation.The formation of rainstorm flood disaster is a complex system and the influencing factors are numerous.Its of certain difficulty to assess rainstorm flood risk quantitatively completely.Further explore is necessary in the followup study