Analysis And Construction Strategy Of Jishou Green Space System Based On Sponge City Concept

With the rapidly extensive development of the city,the relationship between human beings and nature is obviously unbalanced in cities,which leads to the increasingly serious urban problems such as urban waterlogging.In recent decades,the concept of sponge city came into being when flood-stricken city builders began to hope to build sponge city with functions of absorbing water,storing water and purifying water.However,through practical experience,it is found that the sponge function of a city cannot be achieved without the participation of the urban green space system.As the basis of urban ecological balance,urban green space system can effectively control urban rainwater runoff and play an important role in reducing the pressure of urban rainwater pipe network and reducing the risk of urban flood.Due to the canyon topography of Jishou,seasonal water shortages and droughts and floods often occur in urban areas.In the rainy season,urban drainage capacity is inadequate,leading to the serious urban water accumulation.In July 2016,the construction of urban sponge city in new and old areas was officially launched,marking that Jishou is about to enter the ranks of sponge city.Therefore,it is significant to develop the green space system construction strategy of Jishou based on the concept of sponge city.This study acquired the full-color image of 0.5 meters resolution and the multi-spectral image of 2 meters resolution of Jishou,and also preprocessed the image by applying the band feature difference spectral weighting method.After the for steps of image fusion,geometric correction,image intensification and image mosaic and the process of quality inspection,various greenfield interpretation marks were established,and the green space type spatial database was obtained through supervised classification.In addition,by using the DEM elevation data of Jishou,the basic information such as topography,slope direction and moisture information of Jishou were also extracted.Based on the division of street area of Jishou,rainwater collection area of Jishou is divided according to the principle of nearby discharge.Based on the formula and the hydrological information extracted,the comprehensive runoff coefficient of each region was calculated,and the influence of the green space system on the rainwater runoff was analyzed by combining the land type of each catchment area.Finally,the spatial database of green space type and the impact analysis of runoff were combined with the data of field investigation,and based on the sponge city construction background,the Jishou green space system construction strategy was proposed.The main results are as follows:(1)The built-up area of Jishou City can be divided into 9 catchment areas with a total area of 7003.2 ha.The area from large to small is:Wanrongjiang area(1610.4 ha),East Wanrong area(1555.2 ha),Wanxi area(855.5 ha),Tonghe River area(765.2 ha),North WanrongJiang area(700.6 ha),the upper reaches of the Tonghe River area(640.4 ha),the Wenxi River area(545.0 ha),the Datianwan low emission area(205.3 ha),and the Party School low emission area(125.6 ha).(2)There are five kinds of 2,921 green map spots in the built-up area of Jishou,with a total area of 1276.9 ha.The green space accounted for 33.7%of the built-up area.Among the green space,the area of attached green space is the largest(497.1 ha),followed by park green space(289.3 ha)and production green space(227.7 ha),and the smallest is protective green space(111.5 ha).(3)The runoff coefficient values of the nine catchment areas are between 0.387 and 0.866,among which the Wenxihe River area,the Tonghe River area,the North WanrongJiang area,the Wanrongjiang area and the Party School low emission area of all exceeded the standard value of runoff coefficient.The Wenxihe River area has the highest runoff coefficient(0.866),and the upper reaches of Tonghe River area has the lowest runoff coefficient(0.387).(4)The green space system of Jishou has deficiencies in several aspects,such as green space layout,green space structure and green space index.It mainly showed that the green space layout in each catchment area was not reasonable,and the construction of all kinds of green space has not played the role of "Sponge".(5)The green space system construction strategy of Jishou mainly includes:following the concept of sponge city construction,optimizing the structural layout of green space system,strengthening the construction of green space in key areas of water catchment,elaborating the construction of various types of green space,and creating a sample of "sponge green space" renovation and construction by classification.