Hydrological simulation approaches for BMPs and LID practices in highly urbanized area and development of hydrological performance indicator system

Urbanization causes hydrological change and increases stormwater runoff volumes, leading to flooding, erosion, and the degradation of instream ecosystem health. Best management practices （BMPs）, like detention ponds and infiltration trenches, have been widely used to control flood runoff events for the past decade. However, low impact development （LID） options have been proposed as an alternative approach to better mimic the natural flow regime by using decentralized designs to control stormwater runoff at the source, rather than at a centralized location in the watershed. For highly urbanized areas, LID stormwater management practices such as bioretention cells and porous pavements can be used to retrofit existing infrastructure and reduce runoff volumes and peak flows. This paper describes a modeling approach to incorporate these LID practices and the two BMPs of detention ponds and infiltration trenches in an existing hydrological model to estimate the impacts of BMPs and LID practices on the surface runoff. The modeling approach has been used in a parking lot located in Lenexa, Kansas, USA, to predict hydrological performance of BMPs and LID practices. A performance indicator system including the flow duration curve, peak flow frequency exceedance curve, and runoff coefficient have been developed in an attempt to represent impacts of BMPs and LID practices on the entire spectrum of the runoff regime. Results demonstrate that use of these BMPs and LID practices leads to significant stormwater control for small rainfall events and less control for flood events.     

深圳民治河流域低影响开发措施水文效应评估

低影响开发措施为一类较为有效的城市雨洪管理方法,在海绵城市建设中应用较为广泛。为评估其水文效应,以深圳民治河流域为研究区域,构建SWMM城市雨洪模型,设计3种LID措施方案,分别计算不同重现期降雨情形下3种LID措施实施前后的径流过程。结果表明:透水铺装和下凹式绿地等LID措施均对峰现时间有一定的延迟作用,对洪峰流量和径流量均有不同程度的削减效果,且洪峰流量和径流量的削减率均随着降雨重现期增大而减少,透水铺装和下凹式绿地两者的组合实施可以更好地发挥控制径流作用。     

广州市东濠涌流域低影响开发措施雨洪控制效应评估

随着我国城市化进程的快速推进和海绵城市理念的不断加深,低影响开发(LID)措施日益受到各地重视。为评估LID措施的雨洪控制效果,构建基于SWMM的东濠涌流域城市雨洪模型,分析选取适合该研究区域的LID措施,分别采用重现期为0.5、1、2、5、10年的设计降雨对LID措施的雨洪控制效应进行分析。研究结果表明:LID措施能够较为有效地减小流域洪峰流量、径流量及推迟峰值时间,对初期雨水径流污染负荷也具有较好的削减作用,且径流量和污染物削减率均随着重现期增大而减小。     

低影响开发措施的内涝削减效果研究——以济南市海绵试点区为例

本文使用中国水利水电科学研究院自主研发的洪涝仿真模型和洪水风险分析软件(FRAS)对低影响开发(LID)措施的内涝削减效果进行研究。在洪水风险分析软件原降雨产流模型中增加了SCS法,与地面二维水力学模型实时耦合,更精细地反映了LID措施的产汇流过程。结果表明:(1)在5、10和20年一遇24h设计暴雨条件下,LID组合措施在试点区、小流域和街区3个尺度上均能一定程度削减内涝面积,也能在流域尺度上削减径流总量和洪峰流量。措施在5年一遇降雨下内涝削减效果最为显著,径流总量和洪峰流量削减率分别达6.5%和9.7%,在措施布设较为密集的街区内涝面积削减率达48.96%;(2)10年一遇24 h设计暴雨条件下,流域尺度上单项LID措施内涝削减效果各有特点。各措施对积水量的削减效果在降雨过程中均呈先增大后减小的趋势,措施对内涝面积的削减效果排序为下沉绿地透水路面绿色屋顶;(3)措施内涝削减效果与措施类型、措施规模、地形、下垫面条件和措施布设位置密切相关,低影响开发设计时应利用水文水力学模型进行多种方案的模拟分析,合理设置LID措施。     

Life cycle optimisation for highway best management practices.

Highway runoff can cause a number of water quantity and quality problems. Stormwater management systems for highways have been developed based on a fast drainage for large storm situations. Non-point source pollution from highway runoff is a growing water quality concern. Stormwater quality control needs to be integrated into highway drainage design and operation to reduce the stormwater impacts on the receiving water. A continuous simulation/optimisation model for analysing integrated highway best management practices (BMPs) is presented. This model can evaluate the life cycle performance of infiltration and/or storage oriented highway BMPs. It can be directly integrated with spreadsheet optimisation tools to find the least cost options for implementing BMPs throughout a specified life cycle.     

Modeling the Effectiveness of Rain Barrels,Cisterns, and Downspout Disconnections for Reducing Combined Sewer Overflows in a City-Scale Watershed

Green Infrastructure / Low Impact Development (GI/LID) is an increasingly popular strategy to manage urban stormwater for individual properties, but the aggregate effect on runoff reduction at the city scale has not been thoroughly investigated. This study examined the potential combined effects of rain barrels, cisterns, and downspout disconnections on combined sewer overflows (CSOs) for a medium-sized urban center. To support a city-wide analysis, a novel simulation strategy was implemented using the Storm Water Management Model (SWMM). In this new approach, a modeling at the source technique for subcatchment delineation was combined with a set of R-language utilities to automatically configure GI/LID management scenarios. The reconfigured SWMM model was used to examine 99 distinct management scenarios based on different sizes, numbers, and locations of the targeted GI/LID features for the city of Buffalo, New York. For a typical hydrologic year, the deployment of large residential rain barrels (1000-gallon) resulted in up to a 12% reduction in predicted CSO volume, while the inclusion of large commercial-roof cisterns (5000-gallon) contributed up to an additional 12% reduction. Large variations in the predicted CSO reductions were observed across the various management scenarios, and the simulation tools were able to identify locations where the GI/LID features were most effective. In general, the modeling at the source approach and the R-language tools substantially enhanced the utility of SWMM for evaluating the effectiveness of GI/LID deployment as a CSO management strategy at the city scale, and the methodology can readily be adapted to cities with similar CSO issues.

     

Facilitators and Barriers of Applying Low Impact Development Practices in Urban Development

To support sustainable long-term developments and minimize urban sprawl, Low Impact Development (LID) practices have been highlighted for a long time. They are useful, but understanding on LID practices and broadening the LID applications among practitioners is another important task. The main purpose of this study is to understand local professionals’ perceptions on different LID techniques and awareness on their benefits, while also gathering opinions on barriers and incentives. An online survey was delivered to 91 recipients, a diverse pool of stakeholders involved in the Energy Corridor District (ECD) area in Houston, Texas. The majority of the respondents answered that they were familiar with LID. The techniques that have been applied to a larger extent are Detention Ponds and Bioswales. When asked about applying techniques in the future, Retention Ponds, Rain Gardens, Bioswales, and Detention Ponds are highly probable items. Decision-makers identified the major barriers as being the lack of incentives for their application, lack of knowledge of the client, and lack of knowledge of the development team. Education programs would be the most successful incentive, followed by financial incentives and innovations in policy systems. Urban planners have the most expertise in LID practices, followed by architects/landscape architects, while developers were found not to be very familiar with the concepts. This study understands the current and practical opinions about LID from the decision-makers. Different groups understand the importance of education and identified a major barrier as the lack of policy instruments. Some innovation in regulations may elevate proper LID practices.     

Fractional Stochastic Interval Programming for Optimal Low Impact Development Facility Category Selection under Uncertainty

Uncertainties in nature and human society influence low impact development (LID) facility category selection during LID facility optimization distribution, however the investigation of this area is seldom. There are still two problems with uncertainty which influence LID facility distribution 1) how uncertainty factors affect LID facility selection and 2) in the case of a number of LID facilities of multiple categories are to be set, how to construct the LID facility optimization distribution model for LID facility category selection under uncertainty. To handle the problems, this study develops a fractional stochastic interval programming model to process LID facility category selection under the influence of uncertainty. The model can either process multiple objectives via objective maximization and minimization or process the stochastic uncertainty and interval uncertainty. The study shows that the uncertainties which influence LID facility category selection exist in rainfall, infiltration rate, release coefficient, unit price and budget. and the study reveal that the key constraint of LID facility category selection is the uncertainty parameter characteristic of the LID facility, in which different parameters lead to various LID facility optimization schemes. Results of the model include a series of LID facility optimization distribution schemes in multiple scenarios.Results also provide a series of feasible schemes for decision makers, and the manager can select the most appropriate scheme according to water processing level or budget. The developed model could 1) identifying the uncertainty which impact the LID facility distribution. 2) processing the LID facility category selection under interval uncertainty and stochastic uncertainty during LID facility optimization distribution. The method can also be used to estimate the rationality of the LID facility optimization scheme. Moreover, the proposed method is universal and could be extended to other cases of LID facility category selection under uncertainty.

     

Performance of lot-level low impact development technologies under historical and climate change scenarios

Low impact development (LID) systems have potential to make urban cities more sustainable and resilient, particularly under challenging climate conditions. To quantify performance capabilities, modeling results for an array of combinations of LIDs are described using PCSWMM at lot-level to examine performance of individual LIDs on volume and peak flow reductions. Among the four LIDs studied: rain barrel (RB), vegetative swale (VS), bioretention cell (BC), and permeable pavement (PP), PP at lot-level demonstrated the best capability for reducing surface runoff volumes and peak runoff rates under historical weather conditions, while BC showed similar capability for reduction of runoff volumes but minimal peak flow reduction. With PP as the controlling method at lot-level, the maximum percentage reduction of runoff volume for a 2-year storm is 58% whereas for a 100-year storm, the runoff volume reduction is 20%. These results mean the extent of flooding that may arise from the 100-year storm is reduced, but not eliminated. Effectively, the 100-year storm volumes with LID are devolved to have flooding equivalent to a 25-year storm. Under climate change scenarios, performance for all LIDs declined at various levels, where BC was the most resilient LID for a climate change scenario, such that projected 2-year or 5-year storms with climate change will have its impact devolved with LID in place, to result in similar volumes and peaks without LID under historical conditions. Furthermore, even with an assembly of lot-level LIDs distributed throughout the community, there is not attenuation to substantial degrees of flooding for major events, but there can be effective control for water quantity for small (2- to 5-years in particular) storm events.     

低影响开发技术在半山区丘陵地带的应用效果评估

为评估低影响开发技术缓解半山区丘陵地带城市内涝的效用,以河北邢台临城县中心城区为例,结合地理信息系统构建了研究区暴雨洪水管理模型,利用实测节点积水深数据率定了模型参数,验证了模型的可靠性。以此模型为工具,因地制宜布设了各种低影响开发措施,分别对比分析了3a、5a、10a、20a一遇设计暴雨下措施实施前后出水口的流量过程。结果表明:在半山区,低影响开发措施可以改变区域径流过程,使出水口流量过程线较为坦化,起涨时间明显滞后,洪峰平缓。但上述变化均受坡度影响,且消峰减量效果不仅与布设面积有关,还与坡度有关,坡度越小消减效果越明显。洪水总量及洪峰流量消减率随重现期的增大逐渐减小,且控制洪水总量的敏感性优于洪峰;措施实施的滞峰效果和滞峰能力均不明显。研究结果可为区域内开展小尺度海绵措施改造提供决策支持,为其他半山区域的雨洪管理提供参考。     

基于SWMM的透水性路面水文效应分析

LID(Low Impact Development,低影响发展)雨洪调控措施对消减城市洪峰流量,改善生态环境具有重要的意义。透水性路面通过快速入渗径流及减少区域不透水性比例,从而达到消减洪峰的作用。利用SWMM(Storm WaterManagement Model,暴雨洪水管理模型)模拟软件,分别模拟了城市发展前(天然状态下)、发展后无调控措施(普通混凝土路面)及发展后利用透水性路面对2年、10年及100年设计暴雨进行调控的径流过程。模拟结果显示,城市化进程显著增大了洪峰流量,缩短了径流持续时间,透水性路面在消减洪峰流量和洪量方面具有显著的作用。     

Management of agricultural practices results in declines of filamentous algae in the lake littoral

Filamentous algal cover was quantified during periods of peak biomass from 2001 to 2007 in six littoral macrophyte beds in Conesus Lake, New York (USA). Three of the study sites were adjacent to streams that drained sub-watersheds where extensive agricultural best management practices (BMPs) designed to reduce nutrient runoff were implemented beginning in 2003. Three other study sites were downstream from sub-watersheds where only a few or no BMPs were implemented by landowners. For the sites that received extensive management, comparisons of the Pre-BMP baseline period (2–3 yrs) to the Post-BMP period (4 yrs) revealed that algal cover was statistically lower than baseline in eight of eleven years (72.7%). For the three sites where limited or no management was implemented, the percent cover of filamentous algae was lower than Pre-BMP baseline levels in only three of twelve years (25%). Where major reductions in cover of filamentous algae occurred, positive relationships existed with summer stream loading of nitrate and soluble reactive phosphorus to the nearshore. In some cases only nitrate loading was significantly correlated with percent cover, indicating that the relative importance of nitrogen and phosphorus to algal growth near streams may be determined by the characteristics and land use within each sub-watershed. Agricultural BMPs targeting nutrient and suspended solid runoff can effectively reduce filamentous algal growth locally along the lake littoral zone on a time scale of months to a few years and with moderate commitment of resources. This work offers a new perspective for management of the growing problem of littoral algal growth in the embayments and drowned river mouths of the Great Lakes.     

北京未来科技城LID分块配置与径流削减效果监测

LID(Low Impact Development)完整流程包括:目标规划、配置设计、方案优选、施工建设、运行维护、效果监测以及评价改进。对于大尺度区域LID,可基于总体目标分解为不同子目标区域,并结合土地利用类型分为不同类型地块分块配置LID措施。以北京未来科技城为例,介绍了分区分块的LID配置方法,并对未来科技城LID效果开展降雨径流监测。结果表明,相比不采用LID措施情况,径流系数削减率可以达到78%;分析未来科技城雨水综合利用情况,雨水利用主要以入渗补给为主,综合利用率在85%以上。     

基于水文控制目标的中小尺度海绵城市改造方案评价

为正确评价中小尺度低影响开发(LID)措施改造方案的水文控制效能,以重庆市秀山县海绵城市建设试点为例,将LID措施的生态、经济和社会效应具体量化为径流量控制、径流污染控制、建设成本、维护管理成本和径流利用效益等5个指标,构建了基于水文控制目标的LID措施评价体系,并利用暴雨管理模型(SWMM)对不同LID设施改造方案的暴雨径流水文过程进行了验证模拟。研究结果表明:现有LID措施因其规模占比过小且组合方式不合理而对暴雨径流的水文控制效果不佳,不满足75%年径流总量控制率目标,需进行扩容和组合优化;LID设施改造方案综合评价结果显示综合评分与径流总量控制率、峰值流量削减率等水文控制指标呈显著正相关,可直接作为中小尺度海绵城市改造方案评价。     

针对人工海岛的低影响开发建设方案研究

为了研究人工海岛地区低影响开发(LID)方案设计对削减径流污染的效果和通过设置不同的LID设施增大雨水下渗从而降低土壤盐分的影响,利用暴雨径流管理模型SWMM,设计不同目标导向的LID方案。通过SWMM模型中的水质模块分析研究径流污染削减效果,通过建立SWMM模型模拟后的雨水下渗量与地下水潜水层下层水位之间的函数关系对模型中的压盐效果进行分析。结果表明,应根据LID设施的适建范围充分利用各类用地。绿色屋顶对屋面径流污染具有较好的削减作用,生态草沟对道路径流污染有较好削减作用,透水铺装增加雨水下渗以及压盐效果最优,另外设置具有错峰排水功能的雨水罐可取得较好的下渗效果,旨在为人工海岛雨水资源利用规划提供决策依据。     

Area proportion optimization of different LID facilities and effect of runoff pollution controlEI北大核心CSCD

为探究低影响开发（LID）设施对缓解城市洪涝灾害以及削减污染物负荷的效果，以淮南市某老旧小区为研究对象，基于SWMM模型构建了暴雨径流管理模型，分析了单项LID设施不同面积占比时的总成本效益，针对4种LID设施组合方案，模拟了不同设计降雨重现期的地表径流、排放口流量及污染负荷。结果表明：对于单项LID设施，占屋顶总面积45%的绿色屋顶、占不透水道路面积60%的渗透铺装和占绿地总面积10%的生物滞留设施总成本效益最高；不同LID设施组合均有较好的雨洪控制效果及污染物削减效果，但随着降雨量的增大，效果均有所减小。     

The Impact of Uncertainty Factors on Optimal Sizing and Costs of Low-Impact Development: a Case Study from Beijing,China

The facility allocation optimization of Low-impact development (LID) optimization has been used widely to prevent and tackle urban storm water pollution. However, uncertainties existing in nature and human society would influence the size and total cost of LID. To study the influence of the uncertainties on LID optimization allocation, the research develops the model of LID optimization allocation under uncertainty. The principle of the model is establishing primarily the LID optimization model based on certain numbers and identifying the uncertainties. Hence, the model integrates the uncertainty programming, including interval programming, fuzzy programming, stochastic programming, chance constraint programming (CCP) and scenario programming. The model of LID optimization allocation under uncertainty is established with the conditions. The developed uncertainty model tackles multiple types of uncertainties, and the results of the model are in the interval form in multiple scenarios. The model analyses the effects of uncertainties on the size and total cost of LID in this way. The study shows that the uncertainties in rainfall, infiltration rate, release coefficient, funds and unit price all have a significant influence on the size and total cost of LID when these uncertainty factors overlay. A higher violation probability of CCP corresponding to LID sizing results to a wider interval number of the corresponding uncertainty. The developed method of the study is universal, and the method could be extended to other cases of LID optimization allocation to speculate the influence of uncertainties.     

Low Impact Development Measures Spatial Arrangement for Urban Flood Mitigation: An Exploratory Optimal Framework based on Source Tracking

Urban areas are vulnerable to flooding as a result of climate change and rapid urbanization and thus flood losses are becoming increasingly severe. Low impact development (LID) measures are a storm management technique designed for controlling runoff in urban areas, which is critical for solving urban flood hazard. Therefore, this study developed an exploratory simulation–optimization framework for the spatial arrangement of LID measures. The proposed framework begins by applying a numerical model to simulate hydrological and hydrodynamic processes during a storm event, and the urban flood model coupled with the source tracking method was then used to identify the flood source areas. Next, based on source tracking data, the LID investment in each catchment was determined using the inundation volume contribution ratio of the flood source area (where most of the investment is required) to the flood hazard area (where most of the flooding occurs). Finally, the resiliency and sustainability of different LID scenarios were evaluated using several different storm events in order to provide suggestions for flooding prediction and the decision-making process. The results of this study emphasized the importance of flood source control. Furthermore, to quantitatively evaluate the impact of inundation volume transport between catchments on the effectiveness of LID measures, a regional relevance index (RI) was proposed to analyze the spatial connectivity between different regions. The simulation–optimization framework was applied to Haikou City, China, wherein the results indicated that LID measures in a spatial arrangement based on the source tracking method are a robust and resilient solution to flood mitigation. This study demonstrates the novelty of combining the source tracking method and highlights the spatial connectivity between flood source areas and flood hazard areas.

     

Improvement of rainwater infiltration and storage capacity by an enhanced seepage well: From laboratory investigation to HYDRUS-2D numerical analysis

Seepage well is an emerging Low Impact Development (LID) technology that can effectively control the storm runoff. However, its rainwater infiltration rate and storage capacity still require further enhancement. By setting a horizontal infiltration structure at the bottom of conventional rainwater seepage well (CSW), an enhanced seepage well (ESW) was proposed in this study, and its infiltration performances compared with the permeable pavement (PP) and the CSW were systemically investigated using static infiltration experiment and HYDRUS-2D simulation. The results showed that the infiltration efficiency of ESW was significantly higher than that of PP and CSW, and the process of water infiltrated through soil mainly controlled the macroscopic infiltration rate. The Nash-Sutcliff Efficient (NSE) index was used to evaluate the accuracy and reliability of the HYDRUS-2D model, and the results of NSE values greater than 0.75 (varied between 0.75 and 0.91) confirmed the applicability of HYDRUS-2D to describe correctly the hydraulic behavior of the ESW system. Simulation infiltration tests showed that the ESW performed a higher average infiltration rate and fewer total runoff volume than the CSW, indicating the effectively enhancement of the infiltration and water retention capacity of ESW, especially under heavy rainfall intensities. Additionally, the ESW system exhibited an excellent runoff-control and rainwater retention capacity in an actual rainfall scenario.     

Optimal Design of LIDs in Urban Stormwater Systems Using a Harmony-Search Decision Support System

During the last years, climate changes and urbanization are causing huge urban pluvial flood events in many countries in the world, driving to both develop and apply effective and innovative approaches for the design and management of urban stormwater systems. The gradual urbanization is provoking the increase of impervious surfaces and, consequently, of surface runoff and velocity and the reduction of concentration times of watersheds, both increasing soil erosion and worsening the water quality as a consequence of the intensive contamination. In this field, Low Impact Development (LID) practices for urban runoff control can be intended as an effective approach to both improve the urban resilience against the flooding risk and assure environmental interventions to adequate the urban stormwater systems to both climate and land use changes. In this paper, a Decision Support System (DSS) for the optimal design of LIDs in urban watershed is presented and discussed. The procedure is tested on Fuorigrotta (IT) and Ponticelli (IT) urban watersheds, with the aim of assessing the effectiveness of LIDs application in reducing both the flooded and conveyed volumes, at the expense of cost-effective solutions.