A Research For Risk Assessment Of Rainfall Flood Disaster Caused By Land Development In Changsha

Recently,more and more cities have been suffering from rain and flood disaster due to global warming and rapid urbanization.The disaster causes serious loss in terms of economy and personal life.The main reason comes from rapid change of urban base.Hence,original land use pattern and hydrological cycle were destroyed.Technology could be used to deal with the problem of rain and flood disaster risk during urban land-use process,and has been attracting widely attention.The existing land utilization assessment methods neglect rain and flood disaster.Therefore,occurrence of rainwater disasters from the land utilization cannot be avoided effectively.As a result,systemic evaluation of harmfulness of rain and flood disaster,as well as land use pattern,is necessary to develop methods for reasonable urban land suitability evaluation.In the paper,we provide a theoretical technical support to urban management department which is responsible for disaster prevention and mitigation,and reasonable optimizing land use.The method is of importance theoretically and practically.This research focused on the harmfulness of rain and flood disasters of five districts in the city of Changsha.The purpose of the research is to reduce stormwater disasters harmfulness level from the pattern of land use by using GIS technology to research.The main research contents and conclusions are as follows:1.Build research system of rain and flood disasters risk assessment of land use in Changsha City.Through the reorganization and the analysis of the change of land use structure,the impact of land use changes on flood disaster,the research progress of rain and flood disaster risk assessment,the discovery is that urban land use change caused urban land use pattern changes,thereby affecting rain and flood disasters.Therefore,before rain and flood disaster of land use evaluation in Changsha city,the first step should analyze the land use pattern.And then,build a framework of land-use rain and flood disaster risk assessment.2.Retrospective the evaluation of Changsha land use patterns.According to the results of interpretation of Changsha urban remote sensing images in 2000,2005,2009,by using the ArcGIS technology platform,the research analyzed the three periods of land use types,quantity structure and distribution,and land utilization change and synthesis dynamic change.It shows that synthesis dynamic change degree of the five districts in Changsha has reached 8.68%from 2000 to 2009.In particular,the rapid expansion of urban construction land occupied a great deal of woodland,farmland and grassland,which reduced the area of soil infiltration land utilization type,directly causing the destruction of the natural hydrological cycle in the five districts of Changsha,then causing the rain and flood disasters frequently.3.Evaluated and partitioned the risk of rain and flood disasters of land use in Changsha City.First,selecting the climatic factors and underlying factors which impact the rain floods occurrence.That included the land utilization type factor,the present situation river system factor,the soil type factor,the terrain factor and simulation rain runoff factor which is innovative significance.According to remote sensing interpretation about Changsha numeral elevation model,Combining ArcGIS and hydrological analysis methods,we simulated and has obtained the Changsha surface rainwater runoff way.Such potential storm water runoff paths are equivalent to the urban ecological corridors,which are not only can regulate stormwater but also has many kinds of ecological functions.The protection of this potential rainwater runoff corridor is one of the important measures to solve the current destruction hydrological cycle in Changsha City.Secondly,using the ArcGIS technology platform,analyzing the impact of each factor on rain and flood disaster risk,and the evaluation results are divided into 1?9 levels.Thirdly,integrating expert opinion,using the AHP analytic hierarchy process,which determines the weight of each factor and then weighted summation,then we obtain the Changsha 5 level of rain and flood disaster risky district map.In the map,there are low risk area of 58.6700 square kilometers,the low and medium risk area of 152.8944 square kilometers,the general risk area of 128.8928 square kilometers,the medium and high risk area of 105.3452 square kilometers,high risk area of 118.0112 square kilometers which respectively accounts for the total area of 10.41%,27.12%,22.86%,18.68%and 20.93%.Finally,through the danger area land-use structure analysis,the discovery is that the medium-high risk area and high risk area account for the largest proportion of urban land,which is 140.21719 square kilometers and 43.36%of the total urban land.4.The research proposed the optimization plan to the Changsha urban land utilization pattern according to the above analysis.The optimization plan is that,on the basis of rain and flood disaster risk level to partitioning,in accordance with principles of prevention priority,reasonable avoidance,partition to control construction activities in the built up area.For the unbuilt area,appropriate to increase the area of the green space,focusing on protection runoff corridor and connectivity,in order to achieve the goals of the prevention of natural disaster,control and reduction of the rain and flood disaster risk.