Stormwater management of urban greenway in China

In order to improve the stormwater regulation functions of urban greenways on the basis of literature research and case study the relationships between urban greenway and low impact development LID and green stormwater infrastructure GSI are analyzed. Then the classification system of urban greenways is proposed based on their stormwater regulation function and the suitable technical measures for stormwater management which can be used in different kinds of greenways are selected. According to China’s urban planning system the greenway planning method combined with the urban drainage system is developed and the design methods of the greenway stormwater system and individual stormwater facilities are put forward. The relationships between the greenway stormwater system and other systems are also analyzed in terms of stormwater inlet vertical design and overflow.Finally the waterfront greenway and street greenway demonstration projects in Jiaxing City which adopts the above concept and method are introduced. The results show that the reduction rates of annual total stormwater runoff and average total runoff contaminants TSS of the stormwater system are not less than 30% and 40% respectively.

Feasibility assessment of LID concept for stormwater management in China through SWOT analysis

The strengths weaknesses opportunities and threats SWOT analysis method is applied to assess the feasibility of traditional stormwater management and low impact development LID in China.The results show that traditional stormwater management has many disadvantages e.g.only stormwater collection and discharge or flooding peak-flow regulation is taken into consideration but lack of many important functions such as on-site infiltration non-point pollution control ecological treatment etc.Meanwhile as a new stormwater management concept the LID system has many advantages e.g.LID can not only control rainwater quantity but also effectively prevent non-point pollution. Moreover LID is easy for implementation and cost effective and operation and management can also be done easily.LID has attracted more and more attention from governmental authorities at different levels and the majority of practitioners. Therefore LID has bright prospects for wide applications in China.

Strategies for Enhancing the Efficiency of Bioretention Swales and Basins for Urban Stormwater Management in Temperate Region

Among various schemes to reuse and recycle the limited urban fresh water resources, sustainable urban stormwater management, such as water sensitive urban design and rainwater harvesting, has been recognized as one of the most efficient and economically viable approaches. Storm runoff shall be treated as close as possible to its source before it is reused or discharged into public drainage network or receiving waters to enhance the water environment quality. Bioretention swale/basin, which has been commonly applied to treat runoff from roads, car parks, cyclist and pedestrian paths, rooftops, etc., is recognized to be the most efficient and aesthetic pleasing way to harvest rainwater in urban settings, and other longish shape runoff catchment area. This paper studied over 10 bioretention swales/basins applications in temperate region worldwide covering China, Germany, Norway, Austria, USA, and Australia. Key steps in bioretention swale/basin design and implementation in temperate region were investigated, such as strategic bioretention scheme selection, flow conveyance and hydraulic capacity design, filtering media profile, vegetation scheme selection and maintenance scheme, and suggestion and key design parameters. The critical path and parameters of bioretention swale/basin design which enhanced the effectiveness and efficiency of its application for rainwater harvesting in temperate regions were derived.

How to Calculate Stormwater Management and Storage Capacity for Urban Green Space: Multidisciplinary Methods Used in Shanghai City

In order to relieve urban environmental problems due to stormwater runoff,approaches involving the planning of green space for sponge city construction were previously proposed.In this study,water retention characteristics of 168 green spaces are surveyed to develop estimates of stormwater retention in Shanghai City’s center,suburbs and outskirts.Multidisciplinary methods of community investigation,soil tests,artificial rainfall simulation experiments,and simulations in Autodesk storm and sanitary analysis(SSA)and storm water management model(SWMM)are used.The factors affecting the capacity of stormwater management are identified and used to calculate storage estimates.The relationships among rainfall interception capacity(RIC),runoff,soil water storage properties,and vegetative cover are analyzed,which can provide the theoretical foundation for the assessment of the water-holding capacity in urban green spaces.A criterion for the selection of low impact development(LID)techniques for the Shanghai area is developed on the basis of the data from this study.

Stormwater Management in Hong Kong

This paper presents the practice of stormwater management in Hong Kong. It gives an overview of the current situation as regards to the organization, policies and strategies, the technologies adopted, and the economics and financing aspects relevant to implementation of the management practices. The influencing factors and trends in future development of stormwater management are also discussed.

A Community Resilience Evaluation and Optimization Strategy based on Stormwater Management

In the context of disaster normalization,the concept of“resilience”has been gradually introduced into the field of disaster prevention and mitigation in urban communities.In order to resist the increasingly frequent disasters caused by extreme weather,it is necessary to shift the focus of building resilient urban communities to the level of stormwater management.Community resilience is a disaster prevention and mitigation capability based on community resources.In order to solve the deficiency of storm and flood management in the current construction of resilient communities in China,it is necessary to establish a quantitative evaluation system to evaluate it.This paper uses the analytic hierarchy process and Delphi method to establish a community resilience evaluation system from the perspectives of community material space level,community management level and individual level.Then three communities in Hefei City,Anhui Province are selected for practical application of the system,and corresponding optimization and transformation strategies are proposed.The results show that:(1)The resilience of community stormwater management is closely related to the integrated environment of the community,the allocation of flood control facilities and the daily disaster prevention and mitigation management;(2)The ability of disaster prevention and mitigation and the awareness of public participation of the residents in all communities are relatively weak,and the communities invest less in the popularization of stormwater management wisdom;and(3)Resilient communities should not only pay attention to the construction of non-engineering disaster prevention measures,but also to the application of small-scale green infrastructure oriented toward stormwater management.

Application of Urban Green Stormwater Infrastructure in Wetland Park Construction

The positive role of urban green stormwater infrastructure(GIS)and wetland park construction in the process of“sponge city”construction is analyzed by expounding the connotation and problems of“sponge city”construction.Through the analysis of relevant cases,the realization approaches of combing different types of GIS with wetland park landscape design are interpreted,and it is pointed out that different types of GIS can guide the further practice of“sponge city”construction.

Operation and Maintenance Challenges in China“Sponge City”Program

China started a Sponge City program to offset the adverse impacts of urban developments and to tackle many water-related problems.By emphasizing stormwater management practices with“natural solutions”,many positive results have been achieved.The operation and maintenance(O&M)of Sponge City to support long-term success gained considerable focus.China is facing challenges many developed countries have encountered,as well as unique ones due to specific social,economic,and environmental conditions.This study identified and discussed Sponge City O&M challenges:(1)scheduling challenges,(2)technical challenges,(3)in short of local regulation/ordnance,(4)inadequate O&M assessment standard,(5)underprovided training,(6)PPP related concerns,(7)inter-agency coordination needs,(8)ownership and responsible party issues,(9)substandard documentation,and(10)funding and financial concerns.Selected cases and progress in pilot cities are introduced in the discussions.

Gross Pollutants Study in Urban Areas under Tropical Climates

Gross pollutants are the primary targeted pollutants in urban catchment management for urban water quality improvement as well as mitigation of flood. Apart from aesthetically unattractive because of its visibility, gross pollutants also contributes to degradation of river water quality and loss of aquatic habitat as it carries harmful pollutants such as oxygen demanding material, hydrocarbons and heavy metals. This study analyzed trend of gross pollutant generated from two urban residential areas located in Selangor, Malaysia. The median value of gross pollutant load obtained fi＇om the Amanah Apartment and Bandar Botanic are 347.41 kg/ha/year and 32.46 kg/ha/year, respectively. Relationship between gross pollutant wet load with rainfall depths was derived using regression equation. A significant trend of increasing gross pollutant wet load into drainage system with increasing rainfall depth was observed. The behavior of pollutant load is related to the one observed in Australia.

Low impact development technologies for mitigating climate change:Summary and prospects

Many cities are adopting low impact development(LID)technologies(a type of nature-based solution)to sustainably manage urban stormwater in future climates.LIDs,such as bioretention cells,green roofs,and permeable pavements,are developed and applied at small-scales in urban and peri-urban settings.There is an interest in the large-scale implementation of these technologies,and therefore assessing their performance in future climates,or conversely,their potential for mitigating the impacts of climate change,can be valuable evidence in support of stormwater management planning.This paper provides a literature review of the studies conducted that examine LID function in future climates.The review found that most studies focus on LID performance at over 5 km2scales,which is quite a bit larger than traditional LID sizes.Most paper used statistical downscaling methods to simulate precipitation at the scale of the modelled LID.The computer model used to model LIDs was predominantly SWMM or some hybrid version of SWMM.The literature contains examples of both vegetated and unvegetated LIDs being assessed and numerous studies show mitigation of peak flows and total volumes to high levels in even the most extreme climates(characterized by increasing rainfall intensity,higher temperatures,and greater number of dry days in the inter-event period).However,all the studies recognized the uncertainty in the projections with greatest uncertainty in the LID’s ability to mitigate storm water quality.Interestingly,many of the studies did not recognize the impact of applying a model intended for small-scale processes at a much larger scale for which it is not intended.To explore the ramifications of scale when modelling LIDs in future climates,this paper provides a simple case study of a large catchment on Vancouver Island in British Columbia,Canada,using the Shannon Diversity Index.PCSWMM is used in conjunction with providing regional climates for impacts studies(PRECIS)regional climate model data to determine the relationship between catchment hydrology(with and without LIDs)and the information loss due to PCSWMM’s representation of spatial heterogeneity.The model is applied to five nested catchments ranging from 3 to 51 km2and with an RCP4.5 future climate to generate peak flows and total volumes in 2022,and for the period of 2020–2029.The case study demonstrates that the science behind the LID model within PC stormwater management model(PCSWMM)is too simple to capture appropriate levels of heterogeneity needed at larger-scale implementations.The model actually manufactures artificial levels of diversity due to its landuse representation,which is constant for every scale.The modelling exercise demonstrated that a simple linear expression for projected precipitation vs.catchment area would provide comparable estimates to PCSWMM.The study found that due to the spatial representation in PCSWMM for landuse,soil data and slope,slope(an important factor in determining peak flowrates)had the highest level of information loss followed by soil type and then landuse.As the research scale increased,the normalized information loss index(NILI)value for landuse exhibited the greatest information loss as the catchments scaled up.The NILI values before and after LID implementation in the model showed an inverse trend with the predicted LID mitigating performance.

Measuring performance of low impact development practices for the surface runoff management

Continuous urbanization over the last few years has led to the increase in impervious surfaces and stormwater runoff.Low Impact Development(LID)is currently receiving increased attention as a promising strategy for surface runoff management.To analyze the performance of LID practices for surface runoff management,a longterm hydrological modeling from 2001 to 2015 along with a cost-effectiveness analysis were carried out on a campus in Dresden,Germany.Seven LID practices and six precipitation scenarios were designed and simulated in a Storm Water Management Model(SWMM).A cost-effectiveness analysis was conducted by calculating the lifecycle costs and runoff removal rate of LID practices.Results demonstrated that the LID practices significantly contributed to surface runoff mitigation in the study area.The LID performance was primarily affected by the length of the precipitation scenarios and LID implementing schemes.The runoff removal rate of the LID practices fluctuated significantly when the rainfall scenario was shorter than 12 months.When the rainfall scenario exceeded 1 year the effects on the runoff removal rate was constant.The combination of an infiltration trench,permeable pavement,and rain barrel(IT+PP+RB),was the best runoff control capacity with a removal rate ranging from 23.2% to 27.4%.Whereas,the rain barrel was the most cost-effective LID option with a costeffectiveness(C/E)ratio ranged from 0.34 to 0.41.The modeling method was improved in this study by conducting long-term hydrological simulations with different durations rather than short-term simulations with single storms.In general,the methods and results of this study provided additional improvements and guidance for decision-making process regarding the implementation of appropriate LID practices.

Quantitative analysis of impact of green stormwater infrastructures on combined sewer overflow control and urban flooding control

Stimulated by the recent USEPA＇s green stormwater infrastructure （GSI） guidance and policies, GS1 systems have been widely implemented in the municipal area to control the combined sewer overflows （CSOs）, also known as low impact development （LID） approaches. To quantitatively evaluate the performance of GSI systems on CSO and urban flooding control, USEPA-Stormwater Management Model （SWMM） model was adopted in this study to simulate the behaviors of GSI systems in a well- developed urban drainage area, PSW45, under different circumstances. The impact of different percentages of stormwater runoff transported from impervious surfaces to the GSI systems on CSO and urban flooding control has also been investigated. Results show that with current buildup, GSI systems in PSW45 have the best performance for low intensity and short duration events on both volume and peak flow reductions, and have the worst pertbrmance tor high intensity and long durataon events. Since the low intensity and short duration events are dominant from a long-term perspective, utilizing GSI systems is considered as an effective measure of CSO control to meet the long-term controlstrategy for PSW45 watershed. However, GSI systems are not suitable for the flooding control purpose in PSW45 due to the high occurrence possibility of urban flooding during or after high intensity events where GSI systems have relatively poor performance no matter for a short or long duration event,

Green stormwater infrastructure eco-planning and development on the regional scale： a case study of Shanghai Lingang New City, East China

Urban underlying surface has been greatly changed with rapid urbanization, considered to be one of the major causes for the destruction of urban natural hydrological processes. This has imposed a huge challenge for stormwater management in cities. There has been a shift from gray water management to green stormwater management thinking. The green stormwater infrastructure （GSI） is regarded as an effective and cost-efficient stormwater management eco-landscape approach. China＇s GSI practice and the development of its theoretical framework are still in the initial stage. This paper presents an innovative framework for stormwater management, integrating green stormwater infrastructure and landscape security patterns on a regional scale based on an urban master plan. The core concept of green stormwater infrastructure eco-planning is to form an interconnected GSI network （i.e., stormwater management landscape security pattern） which consists of the location, portion, size, layout, and structure of GSI so as to efficiently safeguard natural hydrological processes. Shanghai Lin- gang New City, a satellite new town of Shanghai, China was selected as a case study for GSI studies. Simulation analyses of hydrological processes were carried out to identify the critical significant landscape nodes in the high- priority watersheds for stormwater management. GSI should be planned and implemented in these identified landscape nodes. The comprehensive stormwater manage- ment landscape security pattern of Shanghai Lingang New City is designed with consideration of flood control, stormwater control, runoff reduction, water quality protec- tion, and rainwater utilization objectives which couldprovide guidelines for smart growth and sustainable development of this city.

SWMM-based methodology for block-scale LID-BMPs planning based on site-scale multi-objective optimization： a case study in Tianjin

Low impact development type of best management practices （LID-BMPs） aims to mitigate urban stormwater runoffand lessen pollutant loads in an economical and eco-friendly way and has become a global concern in modem urban stormwater management. A new methodology based on stormwater management model （SWMM） for block-scale LID-BMPs planning was developed. This method integrated LID-BMP chain layout optimization in site-scale parcels with scenario analysis in the entire block-scale urban area. Non-dominated sorting genetic algorithm （NSGA-II） was successfully coupled to SWMM through Python to complete the site-scale optimization process. Different LID scenarios of the research area were designed on the basis of the optimized LID-BMP chain layout. A multi-index evaluation that considered runoff quantity indices, pollutant loads, and construction costs simultaneously helped select the cost-effective scenario as the final planning scheme. A case study in Tianjin, China, was conducted to demonstrate the proposed methodology. Results showed that more than 75% control rate of total runoff volume, 22%-46% peak flow reduction efficiency, and more than 32% pollutant removal rate were achieved. The robustness analysis indicated that the selected final planning scheme was considerably robust with varied weight values.

Determination of urban runoff coefficient using time series inverse modeling

Runoff coefficient is an important parameter for the decision support of urban stormwater management. However, factors like comprehensive land-use type, variable spatial elevation, dynamic rainfall and groundwater elevation, make the direct estimation of runoff coefficient difficult. This paper presented a novel method to estimate the urban runoff coefficient using the inverse method, where observed time-series catchment outfall flow volume was employed as input for the water balance model and runoff coefficients of different catchments were treated as unknown parameters. A developed constrained minimization objective function was combined to solve the model and minimized error between observed and modeled outfall flow is satisfactory for the presenting of a set of runoff coefficients. Estimated runoff coefficients for the urban catchments in Shanghai downtown area demonstrated that practice of low impact design could play an important role in reducing the urban runoff.

Zero increase in peak discharge for sustainable development

For urban land development, some or all natural land uses （primarily pervious） are converted into impervious areas which lead to increases of runoff volume and peak discharge. Most of the developed countries require a zero increase in peak discharge for any land development, and the policy has been implemented for several decades. The policy of zero increase in peak discharge can be considered as historical and early stage for the low impact development （LID） and sustainable development, which is to maintain natural hydrological conditions by storing a part or all of additional runoff due to the development on site. The paper will discuss the policy, the policy implementation for individual projects and their impact on regional hydrology. The design rainfalls for sizing LID facilities that are determined in 206 weather stations in USA are smaller than design rainfalls for sizing detention basins.The zero-increase policy links to financial responsibility and sustainability for construction of urban stormwater infrastructures and for reducing urban flooding. The policy was compared with current practices of urban development in China to shine the light for solving urban stormwater problems. The connections and differences among LID practices, the zero-increase policy, and the flood control infrastructure were discussed. We promote and advocate the zero-increase policy on peak discharge for comprehensive stormwater management in China in addition to LID.

Fifty Years of Water Sensitive Urban Design, Salisbury, South Australia

Australia has developed extensive policies and guidelines for the management of its water. The City of Salisbury, located within metropolitan Adelaide, South Australia, developed rapidly through urbanisation from the 1970s. Water sensitive urban design principles were adopted to maximise the use of the increased rim-off generated by urbanisation and ameliorate flood risk. Managed aquifer recharge was introduced for storing remediated low-salinity stormwater by aquifer storage and recovery （ASR） in a brackish aquiter for subsequent lrngatlon. Ibis paper outlines now a municipal government has progressively adopted principles of Water Sensitive Urban Design during its development within a framework of evolving national water policies. Salisbury＇s success with stormwater harvesting led to the formation of a pioneering w aterbusiness that includes linking projects from nine sites to provide a non-potable supply of 5 ×10^6 m^3 year. These installations hosted a number of applied research projects addressing well configuration, water quality, reliability and economics and facilitated the evaluation of its system as a potential potable water source. The evaluation showed that while untreated stonnwater contained contaminants, subsurface storage and end-use controls were sufficient to make recovered water sale for public open space irrigation, and with chlorination acceptable lbr third pipe supplies. Drinking water quality could be achieved by adding microfiltration, disinfection with UV and chlorination. The costs that would need to be expended to achieve drinking water safety standards were found to be considerably less than the cost of establishing dual pipe distribution systems. The full cost of supply was determined to be AUD$1.57 m ＂ for non-potable water for pubhc open space lrngatlon much cheaper than mares water, AUD $3.45 m at that time. Producing and storing potable water was found to cost AUDS1.96 to $2.24 m .