Influence Of Impervious Surface Expansion On Surface Runoff In Guangzhou

In the process of rapid urbanization,urban and rural construction lands have gradually replaced natural landforms dominated by green vegetation.This change has caused great changes in the city's underlying surface:the impervious surface of the city has expanded dramatically and the coverage of vegetation has decreased significantly.As a result,the quality of the ecological environment has been significantly reduced,and lakes,wetlands,and arable land have become victims of urban expansion.A large number of arable land wetlands have been buried and cofferdams,and the proportion of impervious surfaces in cities has increased,impeding normal water circulation;Under the circumstances,water cannot penetrate into the earth's surface,and the catchment area quickly pools,the surface runoff increases,and the drainage pipe network is overloaded,causing frequent occurrence of urban internal disasters,causing property damage and seriously affecting people's lives.In the context of building a smart city and a sponge city,the river basin and surface runoff in the city have become hot research issues,and the impervious surface related to runoff has attracted much attention.The study of the impervious surface expansion on the surface runoff,the impact of the basin's runoff and the spatial distribution of the process,reveals the changes in surface and river flow characteristics and hydrological processes,and is important for the sustainable development of the city.The significance and research results can provide data support for the reasonable supervision and regulation of water resources in the basin,and provide scientific reference for the city's flood control design and disaster prevention and reduction work.This paper uses Guangzhou as a research area,comprehensively applies geography and hydrology principles,and arranges monitoring stations(velocity meters)at the upper,middle and lower parts of Chebei and installs corresponding rainfall gauges near the monitoring stations to obtain rivers.The measured data of flood flow rate and rainfall combined with RS and GIS technology extracted the impervious surface of Guangzhou during the four periods on the remote sensing image,and analyzed the characteristics of impervious surface expansion and spatio-temporal changes in Guangzhou during different periods;The hydrological model(L-THIA)simulated the runoff at each period,analyzed the variation rules,and used the measured rainfall data and runoff data from September 2016 to August 2017to explore the impervious surface expansion and surface runoff through experimental demonstration.The relationship between.The main results are as follows:(1)Temporal and spatial changes of impervious surface expansion in Guangzhou:During the period from 1990 to 2000,impervious area has been in a growth mode,and the impervious area in Guangzhou has increased from 421.09km~2 to 766.75km~2.During this decade,Guangzhou is impervious to water.The total surface growth was345.66 km~2 with an average annual growth rate of 6.18%.From 2000 to 2010,the impervious area of Guangzhou City increased from 766.75km~2 to 1535.01km~2,with an average annual growth rate of 7.19%.Is was the fastest growing period in the three time periods covered by this study.From 2010 to 2016,the growth rate has slowed down.During the period 1990-2000,the type of land use most occupied by impervious surface expansion was cultivated land;the proportion of occupied land was 40.77%,followed by garden land and woodland;the permeable surface was gradually replaced by hardened surface.(2)The average relative errors between the simulated runoff depth and measured depth values at the three stations of the upper,middle and lower reaches of the flood surging are:5.58%,4.92%,and 6.17%,respectively.The errors are all small and close to the actual measured values.The long-term hydrological model L-THIA can be used for the simulation of runoff.This hydrological model can be used to simulate a small watershed in an urban area.It is especially suitable for watersheds with no monitoring stations and no records,and the simulation results are ideal.(3)The variation of runoff in downtown Guangzhou is:With the development of urbanization,the runoff was increased.The annual runoff of Chebei was increased.During the period from 1990 to 2016,the runoff from the Cheonggyong increased from 129.5621 million m~3 to 178.2936 million m~3,and the runoff increased by43.3315 million m~3,an increase of 33.4%.(4)There are different impervious surface coverages in the upper,middle,and downstream parts of the raft.The impervious surface coverage of the upper,middle,and lower rafts are respectively:25.26%,61.68%,and 87.71%.As the proportion of impervious surface increases,during the rainfall,the peak flow of surface runoff increases,and the runoff coefficient of the river basin increases,leading to the time for flood peak flow to advance.The impervious surface expansion has accelerated the arrival of flood peaks;especially in the case of heavy rain,the peak time has been the most obvious.The larger the proportion of impervious surface is,the larger the rainfall-runoff coefficient is,and the corresponding internal risk is greater.