Shanghai central city environmental hydrology effect of land use/land cover change
Land use/land cover change LUCC research is the forefront of global change research and hot topics at present. Rapid urbanization led to the city scale is continually expanding, high strength and human activity is the sharp change of urban land use/land cover types, formation is different from natural “second city natural landscape,” on the surface of the earth have a profound impact on urban surface hydrological processes.
Urban LUCC hydrological response is reflected on the impact of human activities on urban water cycle ideal object of study.
Paper is located in the eastern plain river network region of Shanghai central city as the study area, from the perspective of environment, ecology and hydrology crossover, using the theory and practice, combining qualitative and quantitative analysis, the method of combining long time scales in urbanization area evolution characteristics of LUCC and research as the breakthrough point, surrounding the water quantity and water quality effect caused by LUCC two main line, discusses the environment of Shanghai city center LUCC hydrological effect, and try to build based on the concept of “ecological drainage” urbanization areas of land use/land cover types of optimization strategy. Paper main research conclusions are embodied in the following four aspects.
1 of Shanghai central city for more than 50 years, experienced a dominant land use types from waters including farmland urban residential land and road square land, residential land, industrial land, and gradually to the city green land conversion polytropic process, gradually to the equilibrium development of land utilization structure, area difference of various land use type is reduced, the heterogeneity of land use structure. For small scale urban remit the waters of the case analysis shows that with the development of the urbanization process, affected by human activities, small scale city link LUCC process is over the waters of the differentiation, deep influence on urban hydrological processes.
Central city for more than 50 years a substantial reduction in water area leads to a significant reduction in the regional ecological service function, sustainable economic development, urban construction speed and population growth is the main driving force. 2 from regional river water system evolution and waterholding capacity, soil moisture content, soil steady infiltration rate, rainfall runoff process level of LUCC was discussed the influence mechanism of hydrological process of Shanghai downtown area.
Research shows that: 1 affected by human activity is significant for more than 50 years of downtown LUCC, resulting in a large number of river stage concentration was filled, makes the city center branch river system than the failure of its decline, drainage, river drainage fractal dimension is unusual, river channel slot storage capacity is less than 70%, more than 50 years ago, river water storage capacity weakened the regional flood control and drainage pressure increased.
2 the land use/land cover types with elevation, soil water content of soil to regulate rainfall runoff capacity significantly, there are no cover plant cover most of the plants, soil moisture content is more than the bare soil, lawn recessed green under low potential ability of soil moisture content and rainfall runoff regulation is superior to the high potential green space and the general elevation; 3 way of land use and cover type and soil crust is a significant difference exists among different types of green space soil steady infiltration rate of the main influence factors.
4 LUCC in downtown rainfall runoff process, causes 2000 to 2003 have increased runoff coefficient. Due to differences between land use type, in the process of urban LUCC, small scale urban hui waters significant differences of land use type change, lead to collect rainfall runoff waters process is put in bigger difference.
With green coverage are 39.13% and 27.36% of the control group, for example, can increase about 10% green coverage to reduce urban rainfall runoff amount and time delay of rainfall runoff flood peak has more obvious effect. 5 the recessed green space and multifunctional aqua green composite regulation system has significant environmental hydrological effect.
In suitable soil steady infiltration rate 1075.0 x 5.0 x 105 m/s, to build the appropriate concave depth 0.1 ~ 0.3 m, area ratio 10 ~ 30% of the recessed green space can be cut for 3 years in a basic design storm return period, continuous rainfall 1 h of surface runoff.
Combined with years of rainfall characteristics, the Shanghai area soil steady infiltration rate, and analyses the current situation of the city green coverage rate shows that in the center of Shanghai city and new urban area under the building or rebuilding the right proportion of recessed green space has the feasibility of the theory. To set the boundary conditions of the urban multifunctional aqua green composite regulation system of rainwater runoff infiltration capacity storage calculation also indicates its good environmental hydrological effect.
3 Shanghai city center of different land use/land cover types of rainfall runoff nonpoint source pollution has strong spatial and temporal distribution characteristics, the main pollutants in the TSS and CODCr is rainfall runoff.
Center of urban rainfall runoff nonpoint source pollution obvious early effect, after the rain is the main causes of pollution in urban surface water body under impact. Inside and outside of different land use/land cover types of rainfall runoff pollutants cut experiments show that the urban green space has significantly cut the effect of rainfall, surface runoff pollutants.
Shanghai central city environmental hydrology effect of land use/land cover change
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