Urban Stormwater Management Pattern In Response To Climate Change And Urbanization

The sustainable development of urban stormwater management(USM)has become important in human settlements construction.Serious urban stormwater issues(e.g.,increasing runoff and floods during storms)may arise due to an increase in rainfall intensity and the frequency of storms as a result of climatic change.In addition,it is generally observed that peak runoff increases sharply with rapid urbanization.Due to the combined influence of climate change and urban development,USM is facing severe challenges with respect to flow control,quality improvement and rainwater utilization.Thus,it is of great significance to scientifically predict the impact of climate change and urbanization on rainfall runoff.However,the research on USM in view of climate change and urban development is limited at present.Based on the knowledge of meteorology,hydrology,economy,civil engineering,urban planning and landscape architecture,this study uses literature review,field research,case studies and model analysis to develop an approach to the design of USM systems in response to climate change and urbanization.First,this study compares USM in two coastal cities:Hong Kong and Singapore.Hong Kong adopted conventional USM for flood control and embraced hard-engineering infrastructure in the scheme.In contrast,Singapore has put in place a series of holistic management practices to manage urban runoff.By comparing the stormwater management practices in these two cities,the differences in approaches to non-structural and structural practices are elucidated.The research shows that holistic USM has significant advantages in core value,target systems,spatial scale and cost performance.Based on this comparative study of USM systems,a holistic USM system,which emphasizes the combined development of structural and non-structural practices,should be the basis for developing stormwater management to face the future challenges.Second,to project the impacts of climate change and urbanization on USM,this study integrates representative concentration pathways(RCPs),shared socio-economic pathways(SSPs),and SSPs at the macro,meso and micro levels of the urban context(SSPa/b/c),and develops a scenario modeling methodology(RCPs-SSPs-SSPa/b/c)for USM.Then,this study analyses the challenges and influences(e.g.,precipitation,flow quantity,and water quality)on USM at the macro,meso and micro levels in Singapore through future scenario modeling.The simulation results are:1.Different scenarios predict different levels of challenge in stormwater management in Singapore,but all scenarios predict that the challenges will become tougher;2.Storms of shorter return periods are more significantly affected than storms of longer return periods;3.In urban catchments,controlling flows and improving water quality after storms of short return periods will become significantly more difficult;4.Peak runoff and contaminant loads are more sensitive to changes in impervious surfaces and progressive urbanization than to climate changes;5.Different responses in flow quality and water quantity are observed at the urban meso level with different land-use and development modes(e.g.,the pressures of commercial and residential land use downtown will be harder to manage than the pressures of industrial and residential land use in developing areas);6.Changes in runoff quality will be more sensitive to changes in flow quantity;7.Low-Impact Development practices could alleviate the pressures on stormwater management from climate change and urbanization.Therefore,to alleviate the adverse effects of future changes and ensure the effectiveness of stormwater infrastructure,practices should be designed with input from future scenario modeling.Finally,based on the comparison of USM systems,future scenario modeling,and application research,this study develops a pattern of USM,including connotation,principles,goals,and methods,in response to climate change and urbanization.The connotation is to maintain a sustainable urban hydrology cycle.The principles are openness,professionalism,and goal orientation in the activities of stormwater management.The goals are to solve the problems at the different levels of USM,and the methods should be integrated with situation analysis,future scenario modeling,management objectives,structural and non-structural practices,and performance evaluation.This study also considers public-private partnerships as critical non-structural practices and bioretention as an important source management practice.This management pattern can be widely used in different cities for the sustainable development of USM in response to climate change and urbanization.