Study On The Optimization Of Landscape Pattern Of Zhengzhou City Based On Stormwater Security

Rapid urbanization process in the past decades has raised the living standards of Chinese people,while urban water problems have also become prominent.Urbanization which leading to the change of land use pattern,quantity and structure,destroys the hydrological cycle process,and causes frequent urban rainstorm and flood disasters.How to achieve sustainable urban rainwater management through scientific planning and regulation is the ultimate goal of this paper.As the key city of the National Central City and the "one belt and one road" important city,the level of urbanization of Zhengzhou will continue to improve.How to deal with the water environmental crisis caused by the rapid expansion of urban space and enhance the resilience of the city against rainstorms and even heavy rainstorms are the focus of the construction of ecological civilization cities in the future.Based on the theory of "landscape ecological security patterns",the whole city of Zhengzhou as the research area,this paper constructs the rainwater security pattern at the urban scale,and puts forward the optimization prospect of the landscape pattern based on rainwater security,which provides practical guidance for urban land use planning and development strategy.The main contents and results of this paper are as follows:1)Quantitative analysis of dynamic changes of landscape pattern and gradient changes in Zhengzhou.TM remote sensing images in 1988,2001 and 2014 were classified to six land use types.Combined with ENVI,Fragstats and other spatial analysis tools,the dynamic changes and gradient changes of landscape pattern in Zhengzhou were revealed quantitatively and the history and laws of urban development over the past 20 years in Zhengzhou were summarized.The results show that in the early stages of urbanization from 1988 to 2001,agroforestry production and urban construction became the focus of the work at this stage.The structure of urban spatial development is a typical "single core" type.It presents the characteristics of circular space expansion of "big cake" type;During the period of rapid urbanization from 2001 to 2014,emphasis was placed on urban green space development and urban construction,and the degree of interference with peripheral patches increased.Several sub-urban centers began to appear in the distant suburbs,and the structure of urban space development was a significant "satellite city" type.It presents the urban sub-centers begin to appear in the far suburbs.2)Construct SCS hydrological model in different periods of Zhengzhou city and analyze the spatial pattern of underlying surface runoff effect.With the help of SCS hydrological model in Zhengzhou,the storm runoff process in a catchment area located in the main urban area of Zhengzhou was simulated,and the influence of factors of underlying surface,rainfall intensity and soil moisture degree on the storm runoff process was emphatically analyzed.The results show that: first,construction land and water have the highest runoff capacity.High yield streams are divided into two types: concentrated and dispersed.High yield flow is concentrated in the north of Xingyang city Mang mountain area and Zhengzhou city center area,scattered in the south of Zhengzhou county city center near.Forest and grassland with high plant coverage and large undulating terrain have lower runoff capacity.The low production area is mainly distributed in the south of Zhongmou county and the high mountain area in the southeast of Gongyi city.Secondly,the urban construction of Zhengzhou city has caused significant changes in the land type structure,and the land structure of high-yielding stream area has a trend of simplified development,and the construction land has gradually become the main land type of high-yielding stream area.Thirdly,the higher the rainfall intensity is,the wetter the soil is in the early stage,and the smaller the impact of land use change in different periods on the rainstorm runoff,that is to say,the difference of runoff yield capacity of different land use types is weakened.Fourthly,under the same soil moisture condition,with the intensification of human activities,land use change tends to increase the surface runoff.The change of land use pattern brought by urbanization weakens the influence of rainfall intensity and soil moisture degree on rainfall-runoff relationship.3)The factor superposition method of "runoff corridor + submerged source area" was used to determine the rain and flood safety pattern of Zhengzhou.Based on DEM data without depression in Zhengzhou,hydrological analysis,3D surface analysis,overlap analysis and other tools of Arc GIS were used to extract the flood flood areas of heavy rain of different frequencies in Zhengzhou,and to identify the key locations and spatial areas of the storm flood security pattern in Zhengzhou.On this basis,according to the discretion of the waterlogging risk,such as right of superposition of Zhengzhou rain submerged area range of different frequencies and different security level runoff buffer zone,Zhengzhou city all space regional is divided into five parts,namely the high risk area,high risk area,the risk area,low risk area and safe area,with quantitative and qualitative analysis method of combining the building of Zhengzhou rain flood safety pattern model.The results show that: first,the high risk areas are concentrated in the main urban areas of Zhengzhou and the discontinuous runoff corridors in Zhongmou county,but there are discontinuous pointdistribution in the runoff corridors of Xinzheng,Xinmi,Dengfeng and Xingyang.Second,the high risk area further extends and expands along the runoff corridor where the high risk area is located,presenting as a discontinuous ribbon space.Third,the middle risk area is basically consistent with the continuous runoff corridor of the city,presenting a linear layout.However,in the main urban area and the southeast area of Zhongmou county,the middle risk area has extended to a large area outside the runoff corridor space.Fourth,the low-risk areas are concentrated in the west of Zhongmou county flake area.Fifth,Gongyi and Dengfeng cities in the west of Zhengzhou are relatively safe due to their mountainous areas,high terrain and good permeability of underlying surface.4)According to the model of urban rainwater and flood safety pattern,improve the urban water network and wetland system,put forward the urban space management and control strategy,and guide the urban landscape pattern to the direction of water ecological civilization.On the macro scale,we should protect the original urban hydrological network,strengthen the connectivity between rainwater corridors and restore the natural water system environment.According to the risk level of urban rainwater and flood disasters,the prohibited,restricted and suitable urban areas are identified,and the planning strategy of grounding surface material space is directly identified.On the meso-micro scale,adjusting the site size and layout,applying low-impact development measures to ensure the implementation of micro-level objectives,so as to achieve the overall purpose of rainwater and flood management.