| In recent years,under the background of the rapid development of urbanization,hardening of the underlying surface caused a rapid increase in urban surface run-off.At the same time,urban floods also increase frequently.The rain flood safety problem has become the hotspots and focus of the world.Therefore,this article starts from the perspective of urban rain flood safety,constructing a land suitability evaluation method based on the rain flood safety.That is to say,creasing rain flood factor in the basis of conventional land suitability evaluation index,so as to improve the traditional land suitability evaluation method.And,from the planning level to achieve the purpose of prevention and reduction of urban rain flood damage.Changsha Su Yu embankment is the research object of this article.Based on the synthesis of hydrology,disaster science,urban planning and other disciplines,this paper using the rain flood risk assessment’s method and technology at domestic and abroad for reference,sets up urban watershed land suitability evaluation method basing on the rain flood safety,and selects Changsha Su Yu embankment as a typical urban watershed area for empirical research.Su Yu embankment area is located in the most low-lying area in Changsha city.And it is vulnerable to be in the threat of flood and water logging control.Therefore,its future development and construction must consider the rain flood safety problem.In this paper,the main research contents and research conclusions are as follows:1.Su Yu embankment rain flood risk analysis and assessment.Apply SCS hydrological model and Arc GIS software to get submerged range and depth of the water under different return period flood scene simulation of the Su Yu embankment,and according to the different water depth,assesses the rain flood risk of Su Yu embankment.Results showed that:Su Yu embankment exists great rain flood safety concerns.In five years a flood return period of 1 hour rainfall cases,nearly half of the field is being flooded,the largest submerged depth has been 538 mm,and with the increase of the flood return period flood,scope expands unceasingly as well as the water depth;In the 100 flood return period(flood control standard)1 hour rainfall condition,ground maximum submerged depth has been 998 mm,the rain flood high-risk groups area of 1015.96 ha,accounted for 45.13%of the total land area.2.Regular land suitability zoning and rain flood risk zoning superposition analysis.First,select the traditional land suitability evaluation indicators,including the terrain slope,slope direction,soil texture,traffic location,the present situation of land use type and location of water resources.Second,use Arc GIS technology platform to analysisthe influence of various factors on land suitability,and composite experts’ suggestions,adopting AHP analytic hierarchy process(AHP),to determine each factor weight and weighted superposition,but also getting Su Yu embankment conventional land suitability zoning map.Thirdly,use Arc GIS spatial analysis tools to overlay analysis the regular land suitability zoning and 100 when the rain flood risk zoning.The analysis results show that conventional land suitability zoning and rain flood risk zoning is superimposed on the poor,such as suitable construction land and rain flood danger zone composite covers an area of 209.77 ha,composite degree is low,only at 21.82%,especially in non-construction land and high-risk groups rain flood the superposition area of only 64.62 ha,composite degree is only 6.36%.So,conventional land suitability zoning can’t reflect the spatial distribution characteristics of the rain flood danger zone very well.If we make the layout of the land according to above method,there is a great rain flood safety hidden trouble.So it is necessary to construct a new method of land suitability evaluation.3.The construction of land suitability evaluation method based on the rain flood safety.First,to better reflect rain spatial distribution characteristics of flood danger zone in Su Yu embankment and make up for the lack of attention in the traditional land suitability evaluation method for land unit level ecological processes,join "the rain flood risk" indicators to explore the land suitability evaluation method based on the rain flood control safety,and get the land suitability zoning map based on the rain flood safety,in those focusing one the conventional vertical ecological processes of land suitability evaluation index above.Second,make land suitability zoning based on the rain flood safety of and 100 once the rain flood risk zoning map overlay and analysis.The analysis results show that flood safety of land suitability partition based on the rain and the rain flood risk zoning is superimposed well,among which suitable construction land and rain hung low of danger degree of composite is 38.41%,as well as the unfavorable construction land and rain flood lower degree of danger composite is 49.95%,unfavorable construction land and rain flood danger area in composite degree was 57.74%.Especially non-construction land and rain hung high danger zone,the composite degrees up to 69.86%.Third,Compared with the above two kinds of land suitability zoning and rain flood risk zoning superposition analysis results,we know that the land suitability zoning based on the rain flood safety’s results can reflect Su Yu embankment rain flood danger zone on the space distribution characteristics more.Therefore,on the basis of layout of the land can reduce ground rain flood safety hidden trouble in a certain extent.4.Put forward Su Yu embankment land layout proposal.On the basis of the above work,taking Su Yu embankment based on the rain flood safety of land suitability evaluation results as the basis,put forward the related Suggestions according to different land suitability zoning.That is,ban all beneath the rain flood ecological safety of city construction and development activities on the non-construction land area,we propose this region to do focus on the surface of the water,ecological park,wetland and so on,playing a role in flood storage and detention water logging;We should not do large-scale development and construction activities on non-construction land,but under a reasonable guide to moderate development,and to repair damaged environment;Encourage suitable construction land and construction land area to be appropriately strengthen urban construction plans,at the same time,according to the current condition,proposing to combine construction land in with green space and water system,set up the low impact development facilities,such as small reservoirs,ecological drainage and the ecological floating island.It is not only increased Su Yu embankment vigor,but also ensure the safety of site of rain flood. |
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