Research On The Influence Of Rainfall Runoff By Urban Green Space

With the rapid development of China,there are more and more problems caused by urbanization.The expansion of impervious surface,the reconstruction of drainage system,and the decrease of vegetation coverage have changed the original hydrological characteristics of cities.Decreasing of urban surface infiltration rate leaded to the significant increasing risk of urban flooding disasters.Analysis about the impact of green space on the rainfall runoff process will provide an objective and feasible reference for the urban rainwater management,and provide a theoretical basis for urban planning to a certain extent.The study used the image of Google Earth in 2015 to extract the urban green space in Fuzhou,Fujian.Rainfall runoff was calculated by modified SCS-CN model.The change of runoff reduction caused by urban green space and the runoff reduction coefficient in different rainfall,hydrological soil group and AMC(Antecedent Moisture Condition)scenarios were explored.According the study,suggestions were given to plan the green space from the perspective of rainwater management.The main conclusions of the paper are summarized as below:(1)The area of urban green space in Fuzhou was 25.18km2,with a 30.64%total vegetation coverage rate.It was divided into 12 function zones.The vegetation coverage rate of the park zone was 81.97%,which was the highest among all the function zones.The vegetation coverage rate of administration and education zone ranked the second highest,which was 34.64%.The vegetation coverage rate of old residential zone was 13.31%,which was the lowest of all zones.(2)The largest value of runoff reduction coefficient was 21.4%,which occurred at the rainfall event of 30 mm under AMC II.The economic benefit of the runoff reduction under this situation is 5.04×106 yuan.(3)SPSS was used to explore the relationships between runoff,runoff reduction and green space patterns.The result showed that runoff,runoff reduction are only significantly related to CA(Class Area).(4)Within different function zones,higher vegetation coverage rate resulted in higher runoff reduction coefficient.The public administration and service zone has the highest runoff reduction coefficient(19.10%)and the lowest runoff coefficient(0.72)among the zones(besides park zone)due to its good green facilities.The runoff reduction coefficient in this zone can be improved by improving the soil texture and planting green plants that have stronger(6.55%)and the highest runoff coefficient(0.84)due to the poor green constrcapability of absorbing water.The old residential zone has the lowest runoff reduction uction.Zone reconstruction was needed in order to improve the vegetation coverage rate and minimize flood risk in this zone.