| In recent years,as with the rapid development of industrialization and urbanization,floods are frequently happened under the background of global warming.The task of flood disaster risk prevention and control is still very arduous.The rapid development of industrialization and urbanization has led to great changes in the territorial spatial pattern,and bringing about a series of ecological and environmental problems.Among them,the unreasonable layout of the territorial spatial pattern has an important impact on the hydrological process,aggravates the surface runoff,and then leads to an increase in the risk of flood disasters.Therefore,researching on management and control of the territorial spatial pattern with the goal of flood disaster risk prevention and control,it is of great significance to prevent,control and mitigate regional flood disasters,promote the healthy and stable development of regional society and economy,and guide the formation of scientific and rational territorial space and landscape pattern.In addition,the development of regional disaster risk assessment can provide reference for the improvement of the current territorial spatial planning content,and can also provide guidance for relevant decision-making departments such as storm and flood management to formulate related management and control strategies.In view of this,applied multi-disciplinary theories and integrated multi-disciplinary methods,this thesis selected Xitiaoxi River Basin in the upper reaches of Taihu Basin,where the flood disasters is prominent as an example,based on the characteristics of territorial spatial pattern,the simulation of surface runoff and the assessment of flood disaster risk,the impacts of territorial spatial pattern on flood disaster risk are discussed.And the paper studies on management and control of territorial spatial pattern based on flood disaster risk prevention and control.The thesis could provide a reference for the management and control of territorial space for flood disaster prevention and mitigation,and help to expand the research field of territorial spatial pattern.Firstly,the article systematically compiles relevant research progress,discusses the shortcomings of existing research.Secondly,based on data of production-living-ecological space,the paper analysis the characteristics of the territorial spatial pattern,runoff simulation of the SWAT model based on territorial spatial pattern and the assessment of flood disaster risk based on runoff simulation results.Thirdly,this paper researches on the impact of territorial spatial pattern on flood disaster risk.Finally,from the perspective of flood disaster risk and territorial security,the management and control of territorial space and landscape patterns are carried out on the basis of mechanism exploration and risk assessment.It can be seen from the above that the research content of the paper follows the logical analysis idea of territorial spatial pattern and runoff response process-flood disaster risk assessment-influence of territorial spatial pattern on flood disaster risk-territorial spatial pattern management and control.The research content,methods,results and conclusions are as follows.(1)The characteristics of production-living-ecological space and landscape pattern.First,the paper extracts the area of the production-living-ecological space in the four periods of 1990,2000,2010,and 2018 in Xitiaoxi River Basin by using Arc GIS 10.5,analyzes spatio-temporal and transformation characteristics.Secondly,the paper calculates landscape pattern index by utilizing Fragstats4.2 software,and analyzes change characteristics of the landscape pattern by selecting nine landscape index closely related to the ecological hydrological process from the two dimensions of patch type and landscape levels in Xitiaoxi River Basin.(1)In terms of production-living-ecological space,it had difference in the area change characteristics of various territorial space,and the spatial distribution pattern was relatively stable.The territorial space was mainly woodland ecological and agricultural production space in Xitiaoxi River Basin.Agricultural production space,woodland ecological space and grassland ecological space showed decreasing trend,industrial production space,and with the increasing trend of urban and rural living space,water ecological space,other ecological space in Xitiaoxi River Basin from 1990 to 2018.The distribution pattern of production-living-ecological space was basically the same from 1990 to 2018.The production space was mainly distributed in the northeast of Xitiaoxi River Basin.The living space was mainly distributed in the midstream and downstream.The ecological space was mainly distributed in the upper and middle reaches of Xitiaoxi River Basin.(2)In terms of landscape pattern,the landscape index and change trend were quite different in the patch types and landscape levels of Xitiaoxi River Basin from 1990 to 2018.In terms of the patch level,CA,LPI and ED of woodland ecological space were the largest.NP and LSI of agricultural production space were largest.IJI of industrial production space was largest.SPLIT of other ecological space was largest.AI of agricultural production space,urban living space and woodland ecological space was larger.At the landscape level,during 1990-2018,TA did not change,NP,CONTAG and COHESION showed a fluctuating and decreasing trend.While LPI,ED,LSI,DIVISION,SPLIT and SHDI showed an overall increasing trend.(2)Surface runoff simulation on the basis of SWAT model in Xitiaoxi River Basin.The paper establishes the SWAT model database,divides sub-basin,analyzes hydrological response units and reads meteorological data by using multi-source data such as DEM,soil texture,production-living-ecological space data and meteorological data.This article runs the SWAT model by setting the warm-up period from 1985 to 1989,the regular rate period from 1990 to 2005,and the verification period from 2006 to 2018.The R~2,Ens,and PBIAS of the regular rate and the verification period have reached the accuracy requirements of the model for the monthly runoff at four hydrological stations of Laoshikan reservoir,Fushi reservoir,Hengtang village and Gangkou in Xitiaoxi River Basin.The paper simulates the surface runoff under the four periods of the territorial space from 1990 to 2018 by substituting the calibration and verification results into the SWAT model,and analyzes the runoff variability under meteorological conditions from 1979 to 2018.The results showed that:(1)The average monthly runoff changes in the four periods were similar.The maximum and minimum monthly runoff occurred in June and December,respectively.Runoff variability all fluctuates as the months increase from 1990 to 2018.(2)The area of territorial spatial type and runoff of different sub-basins are significantly different in the four periods,and the runoff was different due to the different area and combination of territorial spatial type,which are mainly manifested in the urban built-up area has a larger runoff than other areas.(3)The change rate of runoff was different due to the different area change rates of territorial spatial type in different time periods.Runoff variability showed an increasing trend from 1990 to 2018.The low value of the runoff variability mainly distributed in the upper and middle reaches,the median value mainly distributed along the midstream and downstream of the Xitiaoxi river,and the high value mainly distributed in the downstream area.The possible reason is that the reduction of agricultural production space leads to the reduction of runoff,while increase of construction land and the reduction of forest ecological space lead to the increase of runoff.(3)Assessment of flood disaster risk in Xitiaoxi River Basin.According to the disaster risk concept formula of the International Strategy for Disaster Reduction:Risk=Hazard×Vulnerability,based on the runoff simulated by the SWAT model,the AHP-entropy weight method is used to determine the weight and selecting key indicators to build a index system to assess the flood risk under the current territorial space in Xitiaoxi River Basin.The results showed that:there were obvious regional differences in the risk,vulnerability and flood disaster risk in Xitiaoxi River Basin.(1)From the perspective of risk,the upper and middle reaches of Xitiaoxi River Basin are dominated by medium and higher risk levels.The higher risk is mainly distributed in the southeast area of the upper reaches of Xitiaoxi River Basin.The highest risk level is mainly distributed in some sub-basins of the downstream along Xitiaoxi river,while the peripheral areas in the downstream are mainly lowest/lower.(2)From the perspective of vulnerability,the vulnerability of Anji in the downstream and its surrounding areas of Xitiaoxi River Basin is mainly highest/higher level.The vulnerability of the 11,12,and 16 sub-basins and surrounding sub-basins in the downstream is mainly medium/higher level,and the vulnerability of flood disasters in other regions is mainly lowest/lower level.(3)From the perspective of flood disaster risk,the areas with highest/higher flood disaster risk are mainly distributed in the midstream and downstream along Xitiaoxi river and its surroundings.The areas of medium flood disaster risk were mainly distributed in the peripheral sub-basins of highest/higher flood disaster risk,while the areas of lowest/lower flood disaster risk are mainly distributed in the west of the Xitiaoxi River.(4)The influence of production-living-ecological space and landscape pattern on flood disaster risk.This paper analyzes the spatial and temporal evolution of the territorial spatial pattern and assessment of flood disaster risk based on the simulation results of the SWAT model.The paper explores the influence of production-living-ecological space and landscape pattern on the regional flood disaster risk by using geographically weighted regression model and pearson correlation analysis.The production-living-ecological space and landscape pattern have significant influence on the flood hazards.(1)From the perspective of the impact of production-living-ecological space on flood hazards in Xitiaoxi River Basin,the area change rate of agricultural,industrial production space and rural living space has a significant positive effect on the change rate of flood hazards,and the area change rate of rural living space has a significant negative effect on the change rate of flood hazards.The impact of the area change rate of woodland,grassland and water ecological space on the change rate of flood hazards from space to space,but dominated by negative effect,and the absolute value of the regression coefficient of the area change rate of various space has obvious spatial distribution heterogeneity.In addition,there are obvious differences in the risk response characteristics of territorial spatial types in different flood disaster risk areas.(2)From the perspective of the impact of landscape pattern on flood hazards,different landscape indexes of the patch type and landscape level have an impact on the level of regional flood hazards,and the direction and extent are different due to the nature of the landscape index.(5)Regulation and management of territorial spatial pattern based on flood disaster risk prevention and control.Based on the impact of territorial space and landscape pattern on regional flood hazards and the results of flood disaster risk assessment in Xitiaoxi River Basin,the paper summarizes the existing problems in the development and utilization of territorial space.Combining flood disaster risk prevention with landscape pattern,territorial spatial utilization and land management policies,it provides a reference for improving the ability of Xitiaoxi River Basin to resist flood disaster risks and other natural disasters from the perspective of territorial spatial utilization and management.In terms of management and control in territorial space,this paper proposes management and control measures based on ecological,agricultural,construction space and three control lines.In terms of landscape pattern,prevention and control of flood disaster risk are carried out by the construction of landscape index and landscape pattern optimization model.In addition,combining China’s national conditions,territorial spatial planning and land management policies,and drawing on advanced experience of foreign developed countries,relevant management and control measures are proposed. |
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