Abstract
This paper reveals the role of urban green space (UGS) in regulating runoff and hence on urban hydrological balance. The modeling software i-Tree Hydro was used to quantify the effects of UGS on surface runoff regulation and canopy interception capacity in four simulated land-cover scenarios. The results showed that the existing UGS could mitigate 15,871,900 m3 volume of runoff (accounting for 9.85% of total runoff) and intercept approximately 9.69% of total rainfall by the vegetation canopy. UGS in midterm goal and final goal scenarios could retain about 10.74% and 10.89% of total rainfall that falls onto the canopy layer, respectively. The existing UGS in the Luohe urban area had a positive but limited contribution in runoff regulation, with similar responses in future scenarios with increased UGS coverage. UGS rainfall interception volume changed seasonally along with changing leaf area index (LAI) and precipitation, and the interception efficiency was distinctly different under various rain intensities and durations. The UGS had a relatively high interception performance under light and long duration rain events but performed poorly under heavy and short rain events due to limited surface storage capacities. Our study will assist urban planners and policy-makers regarding UGS size and functionality in future planning in Luohe, particularly regarding future runoff management and Sponge City projects.
Highlights
Urbanization disrupts hydrological cycles by replacing the natural pervious cover to manmade impervious cover [1]
Our results suggest that urban green space (UGS) as the dominant pervious cover in urban area could be a valuable ecological resource that can strategically act as urban green stormwater infrastructure through urban forests, including trees, shrubs and pervious ground cover that absorb much of the surface runoff in urban areas
Our results revealed the specific amount of stormwater runoff regulated by UGS and the clear gap to achieve the goal of Sponge City [23]—UGS plays a limited role in runoff mitigation because of limited surface storage capacity
Summary
Urbanization disrupts hydrological cycles by replacing the natural pervious cover to manmade impervious cover [1]. The transformation of land cover includes compacted sealed soil and vegetation elimination, leading to the decreasing capacity of the land to intercept, store, purify, evapotranspirate and infiltrate rainfall [2]. The volume of rainfall runoff rises, the magnitude of peak runoff, and local urban flooding occurs more frequently [3]. UGS, referring to vegetated areas with trees, shrubs or grasses in urban areas, is widely recognized as one way to manage and regulate urban surface runoff due to its positive influence on runoff reduction [4,5,6].
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