Plant Selection and Application of Rain Garden in Southern China

Based on the basic principles of rain garden infrastructure, optimal species for rain facilities such as vegetated buffer strip, vegetated shallow groove, artificial wetland were selected, characteristics, configuration principles and methods were summarized.

On Waterscapes in Urban Residential Area from the Perspective of Rain Garden and Eco-pool Designs

Due to the high cost for operating and maintaining waterscapes, waterscapes in many residential areas have been laid aside and even become pollution sources. Taking MCC Beiluyuan (Residential Area) in Chongqing Municipality for example, concrete strategies of using natural terrains to design rain garden and eco-pool, collect rainwater, construct bottom of the bath, and combine plants were introduced, so as to explore a new approach of creating green and ecological modern residential landscapes.

Modeling 3D Ex-Filtration Process of a Soak-Away Rain Garden

This paper presents a three-dimensional (3D) model developed using COMSOL Multiphysics to understand the 3D ex-filtration process of a soak-away rain garden. With a design hyetograph of 3-month average rainfall intensities of Singapore, it is found that the average vertical ex-filtration rate that is obtained by dividing the average vertical ex-filtration (drained through bottom of the soak-away rain garden, averaged over the simulation period = 720 min, and expressed in m3) by the surface area of the soak-away rain garden and the simulation time step is almost constant regardless of increase in saturated hydraulic conductivity (K) of the in-situ soil and the surface area of the soak-away rain garden as a percentage of catchment area. However, as depth to groundwater table which is measured from bottom of the filter media increases, in between 0.5 m and 1 m of depth to groundwater table, the average vertical ex-filtration rate decreases significantly (by around 15 - 20 mm/hr) and the decrease is almost twice, compared with that between 1 m and 1.5 m of depth to groundwater table. Furthermore, this study shows that for a given K of in-situ, K of filter media, and depth to groundwater table, as the surface area of the soak-away rain garden increases, the horizontal flow coefficient which is defined as the ratio between total horizontal ex-filtration (drained through sides of the soak-away rain garden, summed over the simulation period, and expressed in m3) and total vertical ex-filtration (drained through bottom of the soak-away rain garden, summed over the simulation period, and expressed in m3) decreases. Moreover, for a given surface area of the soak-away rain garden, K of in-situ, and depth to groundwater table, the horizontal flow coefficient decreases as K of the filter media increases. However, it is found that for a given surface area of the soak-away rain garden, K of in-situ, and K of filter media, the horizontal flow coefficient increases as depth to groundwater table increases.

Easy-to-Use Look-Up Hydrologic Design Charts of a Soak-Away Rain Garden in Singapore

As catchments become urbanized due to population growth the impervious surfaces created by buildings and pavements in the expense of permeable soil, depressions, and vegetation cause rainwater to flow rapidly over the landscape. To mitigate the adverse impact of urbanization such as increased flooding and depleted groundwater recharge, around the world, several best management practices, in other words, green infrastructures have been practised, and soak-away rain garden is one of them. However, to have a rapid assessment of soak-away rain gardens on a range of potential hydrologic conditions (e.g., size of the soak-away rain garden, saturated hydraulic conductivity of the in-situ soil, and saturated hydraulic conductivity of the filter media), hydrologic design guidelines or design charts of soak-away rain gardens that are specific for local conditions are not currently available for many regions including Singapore. Thus, in this paper, with a design hyetograph of 3-month average rainfall intensities of Singapore, hydrologic design charts, especially, design charts on overflow volume (as a % of total runoff volume) of soak-away rain gardens are established for a range of potential hydrologic conditions by developing a mathematical model based on Richard’s equation using COMSOL Multiphysics, a finite element analysis and solver software package for various physics and engineering applications. These easy-to-use look-up hydrologic design charts will be of great utility for local managers in the design of soak-away rain gardens.

Multiple Regression Model of a Soak-Away Rain Garden in Singapore

Under the possible hydrological conditions, with a design hyetograph of 3-month average rainfall intensities of Singapore, multiple regression equations on hydrological processes, specifically on overflow volume, average vertical ex-filtration rate and horizontal flow coefficient, of a soak-away rain garden are established based on simulated results of a mathematical model. The model that is based on Richard’s equation is developed using COMSOL Multiphysics. The regression equation on overflow volume and the regression equation on log of horizontal flow coefficient show a very strong relationship with the independent variables (saturated hydraulic conductivity of the filter media, saturated hydraulic conductivity of the in-situ soil, depth to groundwater table, and surface area of the soak-away rain garden). The coefficients of determination of the fitted equations on overflow volume and log of horizontal flow coefficient were 0.992 and 0.986, respectively. However, the regression equation on average vertical ex-filtration rate has high p-values (p-values > significance level, α = 0.01) for saturated hydraulic conductivity of the in-situ soil and surface area of the soak-away rain garden. Thus, forward stepwise regression was used to develop the best regression equation on average vertical ex-filtration rate with saturated hydraulic conductivity of the filter media and depth to groundwater table. The coefficient of determination of the fitted equation was found to be 0.911. These easy to use regression equations will be of great utility for local mangers in the design of soak-away rain gardens.

An Interface to Model 3D Hydrological Process of a Soak-Away Rain Garden

To mitigate the adverse impact of urbanization around the world, several best management practices, in other words green infrastructures, have been used in a way that protect the natural hydrology of the catchment and are more beneficial to the environment. Soak-away rain garden, shallow, landscaped depressions commonly located in parking lots or within small pockets in residential areas, is one of those best management practices or green infrastructures. However, though in the past few decades the mathematical modeling work and the science of computer simulation have enhanced the understanding of hydrological processes, there is still a lack of modeling studies that focus on understanding the three-dimensional (3D) hydrological processes, such as the 3D ex-filtration process of a soak-away rain garden in a sufficient level of details. Thus, this paper develops a 3D mathematical model to represent the hydrological processes of a soak-away rain garden using COMSOL Multiphysics Java API, a Java-based interface of COMSOL Multiphysics. The developed model is demonstrated with a design hyetograph of 3-month average rainfall intensities of Singapore.

Initial impacts of rain gardens＇ application on water quality and quantity in combined sewer： field-scale experiment

Green infrastructures such as rain gardens can benetit onsite reduction ot stormwater runott, leading to reduced combined sewer overflows. A pilot project was conducted to evaluate the impact of rain gardens on the water quality and volume reduction of storm runoff from urban streets in a combined sewer area. The study took place in a six-block area on South Grand Boulevard in St. Louis, Missouri. The impact was assessed through a comparison between the pre-construction （2011/2012） and the post-construction （2014） phases. Shortly after the rain gardens were installed, the levels of total suspended solids, chloride, total nitrogen, total phosphorous, zinc, and copper increased. The level of mercury was lower than the detection level in both phases. E. coli was the only parameter that showed statistically significant decrease following the installation of rain gardens. The likely reason for initial increase in monitored water quality parameters is that the post-construction sampling began after the rain gardens were constructed but before planting, resulted from soil erosion and wash-out from the mulch. However, the levels of most of water quality parameters decreased in the following time period during the post-construction phase. The study found 76% volume reduction of stormwater runoff following the installation of rain gardens at one of studied sites. Statistical analysis is essential on collected data because of the encountered high variability of measured flows resulted from low flow conditions in studied sewers.

由学生自主营造一个全要素雨水花园的困难与经验

校园营造是指在校园内以师生为主体的参与式设计行动。北京大学自2016年开始尝试学生自主参与校园建设的路径,初步形成了以学生社团为平台、多专业学生合作、多方参与,从被动邀请到主动发起的校园建设模式,探索出由学生主导完成从策划、设计、建造到运营的校园空间更新改造的全程参与经验。以其中一个由学生自主营造的全要素雨水花园的营造过程为例,总结了按照PBL要求的学生自主营造中遇到的困难和经验,详细分析了激发和维护学生自主性的策略,为在建成环境中增建雨水花园和更广泛的自主参与式营造提供了可借鉴的行业经验。

LID措施在海绵城市景观设计中的应用

低影响开发(LID)理念是海绵城市的核心要素之一,在海绵城市建设中的措施包括生态植草沟、下凹式绿地、雨水花园、绿色屋顶、地下蓄渗、透水路面等。文章主要从透水铺装、植草沟、雨水花园3方面提出LID措施在市政道路景观设计中的应用研究,并对这些措施下植物的选择提出一定思考。通过实际项目的测试对比得出,当滞留带标准低于10.0mm/min时,道路不存在溢流情况,最大溢流量仅为4.95mm/min,对应的入渗量始终稳定在5.0mm/min以上,可以实现对水资源的有效利用。

基于在线监测的雨水花园系统径流水量控制方法

目前常规的雨水花园系统主要通过搭建绿色屋顶等雨水滞留设施,实现对径流水量的控制,因其缺少对排水管道拓扑结构的分析步骤,导致径流控制效果不佳。针对这一问题,提出基于在线监测的雨水花园系统径流水量控制方法。使用传感设备实现对径流水量的实时监测,并增加蓄存功能;以监测结果为基础,对排水管道拓扑结构差异展开分析,并通过调整模拟降水量、调蓄容积等参数实现对径流水量的控制。结果表明:上述方法可以达成较高的地表径流衰减率,具备良好的径流水量调控能力。

低影响开发在武汉地区中学校园景观设计的应用研究——以武钢三中雨水花园优化设计为例

低影响开发理论已经成为如今城市雨水管道设计中的重要应用基础。而校园景观作为绿地与建筑的重要结合,是与该理论极为匹配的场所。本文希望以武汉地区的中学中心花园为例,探讨低影响开发策略在中学雨水花园设计中所采用的空间与功能相交融的设计模式以及生态与教育相结合的设计目标。并最终将这一模式作为该地区相关改造的典型案例,对更多的校园改造提供建议与借鉴。

基于DRAINMOD模型的雨水花园运行效果影响因素

为研究雨水花园对暴雨径流水文调控效果受不同设计参数的影响,在试验研究的基础上,利用排水模型DRAINMOD分析了雨水花园长期运行效果受其蓄水层深度、汇流面积比以及降雨特征等因素的影响。模型测试结果显示,DRAINMOD可以较好地模拟雨水花园内部水文过程;长序列(1951—2007年)模拟结果发现,试验雨水花园对暴雨径流量削减率的年均值为18.5%,经介质净化的水量占雨水径流总量的76.1%;雨水花园蓄水层深度超过某一临界值后对其滞留效果没有影响;汇流面积比增大,排水量和溢流量均增大;在雨水花园内部增加30 cm反硝化作用蓄水层后,排水量下降了19.2%,雨水花园对径流量的削减率提高到33.5%。可见,增加内部蓄水层后雨水花园对水量削减和污染物浓度去除都具有积极作用。

杭州市雨水花园竹类植物资源应用现状与优化策略

竹类植物具有良好的生态效益和极高的美学价值,但目前竹类植物在雨水花园中的相关应用研究基本空白。采用实地调研与数据分析相结合的方法,对杭州市25个雨水花园的竹类植物资源进行分析,包括应用比例、种类组成、生长状况、应用区域和配置模式。结果表明,调研的25个雨水花园中只有5个种植竹类植物,占比为20%。竹类植物种类仅有3种,分别为小琴丝竹(Bambusa multiplex cv.Alphonso-Karri)、箬竹[Indosasa tessellatus(Munro)P.C.Keng]和刚竹(Phyllostachys sulphurea var.viridis R.A.Young),其中小琴丝竹应用最多。应用区域集中在边缘区和缓冲区,蓄水区中没有应用。配置模式主要为丛植和片植。针对杭州市雨水花园竹类植物资源存在应用比例偏低、种类单一、应用区域不够广泛,以及配置模式单调的问题,探讨了雨水花园竹类植物的多样性提升策略、生态适宜性策略,以及种植区域与配置模式拓展策略。研究结果可为雨水花园和海绵城市建设中的竹类植物资源应用拓展和景观多样性提供参考。

湿热地区雨水花园夏季微气候影响效应——基于成都市圣灯公园的实证研究

作为我国理水治国和城市生态转型的重大举措,海绵城市成为解决水资源和热岛等相关问题的重要契机。雨水花园是海绵城市技术措施中非常重要和普遍的一种类型,下垫面、植物设计、地形差异、水体等几个方面与普通绿地存在差异。通过结合实测和模型模拟等方法深入分析雨水花园中下垫面和植物设计在微气候影响方面的差异。既有研究发现,雨水花园下垫面特有的覆盖层、填料层、砾石层以及不同厚度填料层具有不同的蓄水蓄热能力、雨水下渗速率及土壤水分的蒸发强度,从而影响土壤湿度,形成微气候差异,雨水花园下垫面相较普通绿地降温降湿更显著,对相对湿度的影响大,形成的不舒适指数更低。模拟结果显示雨水花园下垫面更厚,降温的效果更明显。在植被方面,当雨水花园与普通绿地植被类型相同时,雨水花园降温的效果优于普通绿地。雨水花园与普通绿地微气候差异与植被乔灌草的搭配类型相关,当植被类型为乔灌草时,雨水花园与普通绿地的温度和相对湿度差值最大,植被类型为草本时,雨水花园与普通绿地的温度、相对湿度差值最小。相应研究可为多功能雨水花园提供理论支撑,并提升海绵设施的科学性,促进海绵城市建设目标和内涵的充分实现。

基于层次分析法的皖南地区雨水花园植物综合评价与选择

对国家海绵城市池州市的12处雨水花园进行现状调查。采用层次分析法,构建雨水花园植物综合评价与选择模型,对27种雨水花园植物从3个约束层和7个标准层进行综合评价分析。结果表明指标中耐水性、耐旱性、净化水质能力以及可观赏性是最重要的四个指标。千屈菜、芦竹等16种植物综合评价等级为一级,是池州市及皖南地区雨水花园首选植物;迎春、山茶等4种植物综合评价等级为二级,可根据雨水花园构造合理选择区域搭配;石竹、海桐等7种植物综合评价等级为三级,是雨水花园建设的慎选植物。

雨水花园集中入渗对地下水水位水质影响的动态过程模拟研究

为探究地下水埋深较浅的平原地区雨水花园集中入渗对地下水水位水质的影响,以扬州市一高校某校区为研究区,以研究区2018年7月—2019年6月的地下水位实测资料和污染物浓度监测数据为研究基础,结合研究区实际水文地质情况,运用Visual MODFLOW软件构建了地下水数值模型和溶质运移模型,模拟了研究区建立雨水花园前后地下水变化情况及经雨水花园集中入渗后浅层地下水中总磷、硝态氮、氨氮的运移过程。模拟结果显示:(1)相同降雨条件下,建立雨水花园前后地下水的补给和蒸发速率分别增加1.2 m^(3)/day、1.1 m^(3)/day,表明集中入渗能够增加对地下水的补给;(2)模拟期间,总磷、硝态氮和氨氮在地下水中的运移路径与水流方向一致,运移距离分别为11.19 m、71.53 m、6.7 m,且浓度分别降低至0.018 mg/L、0.12 mg/L、0.035 mg/L,水质均达到国家健康标准,未对地下水环境造成显著影响,表明雨水花园能够改善地下水水质。研究结果可为海绵城市建设和地下水污染治理提供参考依据。

北京市海绵城市试点区雨水花园植物群落生态适应性及其应用效果

[目的]针对已建成的城市雨水花园项目,从生物多样性的角度进行多指标调查评价,分析雨水花园植物的适应性及景观应用效果,旨在为北京地区雨水花园植物群落优化配置提供科学参考。[方法]通过实地调研,分析和掌握雨水花园植物群落的多样性特征,在定量分析的基础上构建雨水花园植物群落景观评价模型对15个典型雨水花园植物群落进行分级和评价。[结果]①北京市海绵城市试点建成区雨水花园草本植物共20科,43属,45种,优势科主要集中于菊科(Compositae)、禾本科(Gramineae)、百合科(Liliaceae)、景天科(Crassulaceae)等。试点区各样地指数数值差异较小,各调查样地草本植物丰富度相似,植物物种集中性较一致。②试点区雨水花园植物群落景观综合评价总体处于较高水平,各样地中小区类雨水花园植物群落评价明显高于道路类雨水花园植物群落景观。受所在区域地表径流污染程度的影响,不同样地植物生长情况、群落构成有所差别。[结论]未来还需加强对建成雨水花园植物的定期监测、评估,重视开发本土植物,筛选出优势物种,总结出结构稳定的植物群落配置模式与维护管理手段,为北京市雨水花园植物选择与配置提供科学参考。

雨洪管理在城市公园绿地中的应用及评价

城市快速发展背后带来了许多严峻的水环境和水生态问题,对于城市雨水资源的合理管理和有效利用是解决当下雨水问题的有效途径。公园绿地,作为城市生态系统的重要组成部分,是进行雨洪管理的重点研究与设计实践的对象。城市公园雨洪管理的有效性是实现城市水生态环境与水资源利用的决定因素之一。因此,该研究从公园绿地的角度出发,以徐州城区范围内2处公园绿地为例,分析其雨洪管理的方式方法及应用效果,针对过程中存在的问题提出可能解决的对策,以期为徐州及其他城市公园的雨洪管理提供参考。

次降雨入渗补给系数评估雨水花园补给地下水可行性及计算方法研究

【目的】近年来雨水花园在海绵城市建设过程中得到了广泛应用,但其对浅层地下水的补给能力尚缺乏系统研究。【方法】通过柱状模拟试验,研究了不同降雨条件下,次降雨入渗补给系数(α)用于评估雨水花园补给地下水潜力的可行性。【结果】结果表明,α可用于评估雨水花园补给地下水潜力,数值变化范围为0.110~0.212,平均值为0.175;降雨重现期、降雨历时、雨型均对α具有重要影响,且随着重现期和降雨历时增加,α逐渐降低,不同雨型条件下,α大小顺序为均匀雨型>双峰雨型>单峰雨型。【结论】HYDRUS-1D模型模拟法和包气带含水率法计算α均具有较好的精度,不同降雨条件下,模型模拟法计算得出的次降雨入渗补给系数(α_(m))的相对偏差(RE)为-1.280%~7.801%,包气带含水率法计算得出的次降雨入渗补给系数(α_(b))的RE为-14.789%~6.660%。由于包气带含水率法容易实施、便于监测,工程实践中可优先考虑采用该方法。上述结果可为定量评估海绵城市建设过程中雨水花园补给浅层地下水潜力提供参考。

深圳地区8种园林地被植物耐涝性综合评价

为高效筛选雨水花园适用植物,以香彩雀Angelonia salicariifolia等8种园林地被植物为试材,采用盆栽模拟涝渍的方法,研究不同时间淹水胁迫处理后8种植物的观赏性状及生理指标,通过主成分分析与隶属函数法对其耐涝性进行综合评价,并筛选评价植物耐涝性的有效指标。结果表明,8种园林地被植物的耐涝性强弱依次为香彩雀、水鬼蕉Hymenocallislittoralis、龙船花Ixorachinensis、朱槿Hibiscusrosa-sinensis、大花马齿苋Portulacagrandiflora、朱蕉Cordylinefruticosa、巴西野牡丹Tibouchinasemidecandra、四季海棠Begoniasemperflorens;植物叶片的相对含水量、MDA含量、相对电导率与Fv/Fm值是反映植物耐涝性的重要指标。