International Low Impact Development Conference China 2016: LID Applications in Sponge City Projects

Extreme weather frequently causes torrential rains and flooding in modern cities, e.g., Beijing, which are much sensitive and fragile to flooding disasters because of high population density. In this study, we aimed to quantify the temporal and spatial distribution of extreme precipitation in Qinghe Basin in Beijing and to develop optimal flood management thresholds by using precipitation records from 1986 to 2014 in two sites of the region. The time that maximum precipitation occurs in a year differed temporally and spatially and mainly concentrated in July and August. Extreme precipitation amount covered 41.7% of total precipitation in a month during flood season. Rain days of rainstorms were on average 1.7 d and 87% of them concentrated in July and August and were more in upstream than that in downstream. Precipitation intensity (SDII) during flood season was on average 11.7 mm d^–1 and highest (15.1 mm d^–1) in July. SDII during critical flood control period increased in upstream during recent 30 years and implied a high flood risk in the future. The spatial distribution of precipitation intensity was significantly different. Our results at basin level would help city authorities designing optimal flood control constructions, drainage facilities, and warning systems.

Low impact development (LID), which aims at either infiltrating, evapotranspiring or storing water at the source, plays an important role in managing urban rainwater. This paper summarizes the effects of four individual LIDs (i.e., bioretention, green roof, porous pavement, and grass swales) and several combinations of those LID practices on rainfall-runoff management. The survey shows that both individual and combined LIDs are effective in controlling small and medium rainfalls, and the performances are less obvious with increases of the rainfall depths. Hence, the individual or combined LIDs applied with noticeable effects on low or moderate rainfalls might not be useful for heavy rain events which would probably cause urban floods in cities in China. Cities located in different regions show big differences in rainfall characteristics. Rainfall intensity is an even more important factor than rainfall depth that influences performances of LID practices. In the future, more studies should be directed to the effects of LID measures on large storm runoff managements under different rainfall intensity-duration-frequency (IDF), which would be helpful to select suitable LID practices for cities in China.

Various low impact development (LID) measures have been proposed to mitigate the negative impact of urbanization. The infiltration-type LID devices, such as rain gardens, have been found effective in restoring some predevelopment hydrology through focused recharge to groundwater with enhanced infiltration. However, the focused recharge from LID devices may bring pollutants down to the groundwater and poses potential threat to water quality. The magnitude of such negative impact is subject to several environmental factors, including rainfall pattern, water table depth, and the soil properties. This research presents a field monitoring study on the effect of rain garden infiltration on local groundwater dynamics and water quality in Xi’an, China. The preliminary results showed that even sparsely distributed rain gardens had certain effect on groundwater dynamics, forming a groundwater mound underneath the recharge point; the effect of focused recharge on groundwater quality was even more significant. Further investigation is needed to determine the regional effect of more densely constructed LID measures on groundwater dynamics.

In order to relieve urban environmental problems due to stormwater runoff, approaches involving green space planning for sponge city construction was previously proposed. In the current study, water retention characteristics of 168 green space was 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’s Storm and Sanitary Analysis Storm Water Management Model were used. The factors affecting the capacity of stormwater management were identified and used to calculate storage estimates. The relationships among the rainfall interception capacity, runoff, soil water storage properties, and vegetative cover were analyzed, which provided 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 can be developed based on the data from this study.

This article takes Beijing as the representative research city, analyzes current laws and regulations about urban rainwater. It puts forward seven basic factors of rainwater storage and infiltration and works out the “4+1” comprehensive control index system of rainwater which consists of 4 indexes of rainwater and 1 index of sediment removal. Moreover, based on city planning and urban water and soil conservation of Beijing, the “3-5-7-9” comprehensive index system of rainwater had been built. Some application cases of the Beijing economic-technological development area are presented to demonstrate the features and functions of “infiltration-storage-utilization-drain” rainwater system, which based on the “3-5-7-9” series of rainwater controlling index system. The studies not only have a great significance of strengthening the city flood prevention and control in northern city, but also promote the development of urban LID technology.

Best management practices (BMP) techniques which aim to preserve natural landscape features, reduce the impervious area, and mitigate non-point source pollution, have become popular in land development. This paper focuses on proving the effectiveness of BMP techniques via the water quality analysis. In this study an area, in South Florida, USA, was selected, which has 9 monitoring stations and a 30 years BMPs planting history. Water quality parameters are collected from 1980s to 2014, and the BMP facilities are deployed in the area from 1980s up to now. To catch the temporal variation characteristics of water quality measures, this study firstly compares two multivariable statistical water quality analysis methods—the exploratory factor analysis (EFA) water quality index (WQI) and the Canadian Council of Minister (CCME) water quality index (WQI). Comparison results show that EFA-WQI can accurately explain the trend and variation of long period water quality statistics. After this, the Mann-Kendall's test is used to detect water quality temporal change trends which indicate the impact of BMP techniques on the research areas. Analysis results show that the water quality index of most research area show a decrease trend over 30 years, and show some short-term decrease or increase trends during the 30 years. These phenomenon indicate that the application of BMP techniques has a long term benefit of gradually improve the environment.

According to the hydrodynamics effects of all kinds of low impact development (LID) engineering properties in the rainfall-runoff process and its conditions, 6 LID attributes indexes including transfer, detention, pollution interception, economic, feasible analysis, and landscape are proposed. In the specific project, 6 basic attributes indexes are quantified as specific scores based on their characteristics, then the degree of engineering implementations is aggregated as weighted averages of the corresponding surface types, so as to obtain a comprehensive evaluation in 6 attributes indexes and obtain the quantitative evaluation of LID combinations; finally, the paper would provide the scoring system of the effectiveness of LIDs in stormwater control engineering. In this paper, the study area is a small watershed in A City, Hunan Province. To judge the rationality and feasibility of this method, the attribute index evaluation method would be applied to evaluate 6 LIDs including pervious pavements, green roofs, sunken greenbelts, bioretention cells, grass swales, and infiltration trenches. On the other hand, the Infoworks Integrated Catchment Management (Infoworks ICM) is used for hydrologic simulation, and two indicators annual total runoff control rate (ATRCR) and total suspended solids (TSS) removal rate are figured out. Comparing the model result with the scoring system (especially the index “pollution interception”), it suggests a correlation study between the two methods. So, it is initially confirmed that the attribute index evaluation method proposed in this paper can provide the preliminary screening, which has a significant practical guiding for the project.

Raingardens are one of several versatile low impact design (LID) approaches; they have a significant effect on controlling runoff, groundwater recharge, and water quality. Much research has been done on the performance of raingardens (laboratory and field scale). However, most studies have focused on pollutant removal, and there is relatively little research to specifically quantify actual evapotranspiration from a raingarden. Actual evapotranspiration is a major component of the water cycle, but it is difficult to measure evaporation and transpiration directly and separately. For this study, the Hooton Reserve Raingarden (located in Albany, Auckland, New Zealand) was selected as the research site. An overview of hydrological and meteorological field experiments is presented. Although field-based hydrology research is more expensive than computer-based research, and is accompanied by many risks and difficulties, field-based research can bring new fundamental understanding and mechanistic explanations of processes. It thereby contributes to hypothesis development.

Centralized water management system has problems about water supplying and flood control as it manages rainwater only for single purpose. When rainfall occurs, the system discharges rainwater quickly to end of the basin as priority without consideration about using rainwater as a water resource on-site. It has negative effects as it consumes excessive energy to treat and supply water from water treatment plant. Above all, the centralized water management system increases flood risk occurrence potential by dealing only peak flow rate at end of basin. Climate change and urbanization makes centralized water management system worse. Accordingly, in this research, we introduce multi-purpose decentralized rainwater management system as a solution which supplies water and controls flood concurrently. First, design type and installation place of decentralized rainwater management system (DRMS) is suggested. Second, flooding risk reduction potential through evaluation of runoff reduction and flood occurrence is quantitatively measured using XP-SWMM. Third, potential for rainwater harvesting potential for water resources securement is quantitatively measured. Detail factors to measure the effects of water resources securement are usable water volumes, energy saving amount, and pollutants load. Finally, we suggest optimum design type of DRMS and analyze the effects of design improvement at existing drainage system. When total volume of the rainwater storage tank (RST) is same, study results showed more and smaller RSTs are installed the better runoff reduction at end of basin. This result means flooding risk reduction effect of DRMS. The effect of runoff reduction was most favorable in case of MWS-a type. These results mean that we can find optimum design type of DRMS to improve flood risk reduction potential. Also on-site control of rainwater through the DRMS affects water quality positively as catchment area changes. It is expected to use guideline to decide optimum volume of RST from a decision maker related to urban water management of a government.

Vegetated dry swales were designed to promote infiltration, retain storm water, and reduce the surface runoff peak flow. As an important part of swales, the underdrain system, filled with gravels, was usually equipped with a perforated pipe to drain water from upper layers during rainfall events. In most existing models (e.g., SWMM) that were widely used to simulate the hydrological process for vegetated dry swales, outflow from the underdrain system was usually simplified as orifice flow related to water head, and the hydraulic process in the gravel layer and in the perforated pipe on the bottom of the swales could not be described. A hydraulic model of vegetated dry swales was developed in this study by combining an overland flow model, an infiltration model, and an underdrain streamflow model. The flow in the underdrain system was divided into two sections, i.e., the flow through the gravel channel and the flow through the perforated pipe. The former was simulated through a permeability model for porous media, and the latter was described by applying an equation. For the development of the function, data were collected for the calibration of parameters in field tests in Shenzhen, southern China, and water infiltration rate from the gravel channel to the perforated pipe was assumed to be proportional to the water head in the gravel channel and the orifice area on the perforated pipe. Combining an overland flow model, an infiltration model, and an underdrain streamflow model, the vegetated dry swale model was performed to analyze surface runoff retention and underdrain streamflow performance in a dry swale with a perforated pipe after calibration and validation with measured data. The study demonstrated that the proposed model could accurately describe the hydraulic process in the underdrain system of a vegetated dry swale and advance better understandings of dry swale hydraulic performance.

In the planning and design of LID facilities, the analysis and calculation about the operation effect should base on the long time series rainfall process, which cover several years or even decades. In addition to the randomness of rainfall, the natural hydrological cycle determines the relative periodicity and stability of rainfall in the same period of a year. The process of alternate occurrence of rain (wet) or no-rain (dry) can be regarded as a first-order Markov process, and the rainfall in each hour follows two-parameter gamma distribution. Rainfall in different period of a year is simulated with gamma distribution but with different estimated stochastic parameters. The rainfall process of ten years was generated with the random prediction of rainfall per hour. The comparison shows that the average monthly, annual rainfall, and other characteristic values of the simulated data are well coincide with the historical data, which proves that the method is feasible.

In this study, storm water management model (SWMM) was coupled with environment fluid dynamic code (EFDC) to investigate the effects of low impact development (LID) controls at urban catchment scale on mitigating the nutrient pollution in Deep Bay, southeastern China. Six scenarios with different area percentage of LID practices were proposed and simulations were carried out using an annual historical rainfall in 2014 and the 0.25-year return period (T=0.25) design rainfall event. The output rainfall runoff nutrient loads (RRNLs) from the Deep Bay Basin and water quality variations were observed using ocean-land coupled model. RRNLs mainly occurred during May and September, with 2866.6t dissolved inorganic nitrogen (DIN) and 169.7t phosphate (PO₄³-P), accounting for 77% of the annual load. The RRNL reduction rates had a positive correlation with the area LID practices with annual historical rainfall and design rainfall event. The annual reduction rates for DIN and PO₄³-P were approximately 58.1% and 62.3%, respectively, when the LID practice area accounted for 90% of impervious land. The monthly mean concentration of seawater nutrient decreased with the increase of the LID practices’ area percentage to impervious land area. Configuring 90% impervious land to LID practices, the maximum monthly mean concentration of nutrient could be reduced by about 15.2%~18.3%. And the peak concentration of seawater nutrient could be decreased by about 15% after episodic event and be delayed about a half day. The impact of rainfall runoff load from basin could be alleviated by LID practices, thereby mitigating the nutrient pollution in coastal zone. The method and simulation results in this study will provide a scientific basis for integrated coastal zone water environment management and LID practice planning.

In this work, the storm water management model (SWMM) was used to evaluate the performance of bioretention systems as retrofitting technologies at a college campus in Beijing, China. The hydrological model was calibrated by using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The performance of bioretention systems on controlling quantity of the storm rainfall runoff was analyzed and compared with a conventional drainage system under different storm scenarios. The results indicated that bioretention systems were more effective in reducing runoff volume. The total runoff volume and the peak flow in a heavily urbanized catchment were reduced by up to 27.07%~33.55% and 11.13%~15.38%, respectively. The paper also indicated that the performance of bioretention systems was affected by the storm intensity and the location of peak rainfall intensity. This research provided an insight into the performance of bioretention systems designs under different conditions, which was essential for effective urban stormwater management.

In order to achieve the balance between the effect of pollutant control and the cost of LID construction, the water capture volume should be properly determined. Generally, the water quality capture volume (WQCV) is optimized by using empirical model. In this study, a mechanical wash-off model with one-dimensional kinematic wave equation is calibrated and validated by two rainfall events collected in Shenzhen, China. Then, this model is used to derive the WQCV with the normalized runoff volume and pollutant mass. With a relatively high Nash coefficient in simulating TSS concentration (0.56~0.91), the model draw to the conclusion that the first 55% runoff volume contains 80% pollutants, which is similar to that of empirical model. Therefore, although mechanical model scientifically illustrates the wash-off process, it is reasonable to use empirical model because of the heavy calculation of mechanical model.

In modern urban drainage systems, most of non-point source pollutions collected by rainwater pipes will finally discharge the pollutant into the nearby rivers. To figure out the pollutant migration path from sub-catchments to rivers, and then alleviate pollutants’ aggregation, the distribution analysis of non-point source pollutions is of great importance. In this study, an area in Bao’an District at Shenzhen, China, is selected and six monitoring stations are set along two rivers (Xin’zhen River and Xi’xiang River). Part of the water quality statistics are collected though field observing, and the other part is modeled using the software. To detect the non-point (NPS) pollution distribution more accurately, both a small subregion and the whole research region are considered to analyze the NPS pollution distribution. The pollution load inside each region is simulated by storm water management model (SWMM) and a polluted index is proposed to represent how seriously the region is polluted, and then, the pollution distribution can be depicted. The pollution components inside each small region are detected for further understanding of the pollution character inside each region. We use multivariate statistical analysis methods including principle components analysis (PCA) and explore factor analysis (EFA) to detect the inner relationship between different water quality parameters and then explore specific pollutant remove strategy for different sub-regions. Finally, this study provides a comprehensive NPS pollution reduce suggestion for pollution removing and the arrangement of pollution control strategies.

The study utilized a geostatistical model to run a spatial simulation and interpolated with site mean concentration (SMC) precisely and calculated the load of suspended solid (SS) by rasterizing the interpolation layer. The results show that (a) non-point source (NPS) pollution at Lingang New City is under a high level, and the mean of P_SS, P_COD, P_TP, and P_NH4+ (P is pollution index of single factor) is 9.61, 2.45, 2.77, 3.07, respectively, while the maximum of P_SS is 40.29; (b) the theoretical semi-variance model for SMC_SS is Gaussian model and spatial structure proportion C₀/(C₀+C) is 0.144, indicating that SMC_SS is strongly spatial-correlated to the study area; (c) the load of SS of NPS pollution is 1012.29t/a, within which 97.39% of the pollution load is from road of effective impervious surface (EIA); and (d) some adaptive management strategies are proposed to control local NPS pollution, including low impact development (LID) practices, reusing runoff from roof of EIA.

Urban flooding is becoming an increasingly important issue in the 21^st century, due to climate change and urbanization. Traditional methods of extensive flood-control infrastructure are challenged. Micro-scale rainwater management which stores some of rainfall from building rooftops can reduce flooding of nearby sewer systems. And the reduction of peak runoff can then calculated using the rainfall-storage-discharge (R-S-D) model. By controlling drain pump, flooding can be further mitigated without costly changing the existing systems, working toward resilient and sustainable flood mitigation approach. The reduction of peak runoff can be calculated using the rainfall-storage-pump-discharge (R-S-P-D) model. From the R-S-P-D model, TPP curves and TPD curves are developed to determine the reduced peak flow and increased design return period for a combination of tank volume and pumping rate. These curves will be used in the design and operation of rainwater systems in areas of limited sewer capacity or for climate change adaptation.

The increase in impervious area caused by development project has led to proper water management dealing with climate change which can affect the water cycle, including the ecosystem. It has been pointed out as a major cause of water pollution according to the increased runoff from nonpoint source as well as the cause of disasters such as floods and inundation resulted from heavy rains. LID techniques have been widely applied in order to recover water environment conditions prior to the development reducing the impervious area. Although the study on the optimum type, the number and placement of LID facilities suitable for area characteristics is being carried out, it is difficult to determine the efficiency of actual LID facility including the effect of runoff reduction from the combination of LID facility. Consequently, this study analyzes runoff characteristics for the units and combination of LID facilities through actual LID design practices and investigated the effect of runoff reduction and climate change responsiveness for the combination of retention-infiltration facilities as the rainfall scenario. The result confirmed that a combination facilities has about 10% or more of the peak runoff reduction than the single one, observed more outstanding effect of runoff reduction in combination facilities higher the storage capacity of among combination facilities. Particularly, when the proportion of retention-infiltration is 1:2 (1,000 m³-500 m²), it was possible to obtain up to 26% or more of the peak runoff reduced. When LID techniques are applied to areas similar to the present study, runoff reduction can be predictable based on the results from this research. Based on the all the method and guidelines for optimum capacity selection of combination facilities of retention-infiltration to achieve the targets of runoff reduction, the approach method proposed by this study can be used as a reference for LID design of future projects suitable for the condition and characteristics of target area.

As refractory pollutants, PAHs could accumulate in bioretention systems and raise environmental health concerns. This study intends to investigate the degradation capability of five indigenous bacterial consortia, originating from petroleum-contaminated soils, enriched and acclimated on a mineral salt medium utilizing pyrene (PYR) as the sole carbon source. The results that, consortium W had a stable and relatively high PYR removal rate of 91.5% at an initial PYR concentration of 50mg/L after 14 days of incubation. Yeast extract and succinic acid were determined as the optimal nitrogen and carbon sources for biomass growth and PYR degradation capability. Under high concentration of PYR (1000 mg/L), the consortium W was still very active in removing PYR. The high-throughput sequencing results indicated that genus Pseudomonas and Achromobacter were the two predominant bacterial groups in consortium W. If properly optimized and controlled, consortium W may play an important role in the bioaugmentation treatment in the bioretention sites containing high concentration of PYR.

Impervious surfaces have become common due to traditional urban development and construction. However, it may affect the urban ecosystem and have negative impacts on the quantity of base flow due to the infiltration decrease. Currently, low impact development (LID) has received increasing attention because it is able to increase base flow by increasing the infiltration rate. However, the effects of LID on the base flow in urbanized areas have not been fully discussed. In this paper, the Hydrological Simulation Program-FORTRAN (HSPF) is proposed to evaluate the impact of LID planning on base flow of an urban area in Shenzhen, China. Meteorological data, a topographical map, land use data, and remote sensing data of this study area are used as inputs in the model. Besides, three months of observed hydrologic data of the watershed in 2015 is used for calibration and validation. The model, coupled with a digital filter method, is used to analyze the change of base flow due to urbanization with and without LID impacts. The results indicate that, under extreme ideal circumstance, the maximum area (48%) of impervious surface is retrofitted to LID. The maximum potential base flow increase in the study area is 15%, which is far more than that in realistic world.

The ecological detention facility, one important rainfall utilization measure, has the remarkable effects on urban rainwater runoff control. Owing to its characteristic of stronger permeability, it is also important to replenish groundwater in the areas around them. In our work, the effect of ecological detention facility on groundwater replenishment was analyzed through developing groundwater modeling system model using the typical rainfall events of studied sites. In addition, the case study based on the real rainfall data of Beijing was carried out on groundwater replenishment difference between under an ecological detention facility scenario and under no ecological detention facility scenario to demonstrate the groundwater replenishment effect of the ecological detention facility. Our research is helpful to promote rainfall utilization technology of ecological detention facilities through providing quantitative results.

To solve the sanitation problems and achieve the resource recovery goal, a new toilet system using FO (forward osmosis) as the key unit was developed. The FO membrane module was used for enrichment of source separated urine collected by vacuum toilets. After enrichment, the volume of the urine was greatly reduced and could be conveniently used as a fertilizer. Lab experiments were carried out to decide the optimal operation conditions of the FO system, and 2 M NaCl was used as the draw solution with cross flow velocity of 55 cm/s. In this condition, an average water flux about 2.5 LHM, rejection rate over 80%, and concentration times of 2.5 were achieved. A pilot scale toilet system with 6 stools was built to testify the operation result. The result showed that the system produced high quality fertilizer without addition of water and other substances and the quality of the reclaimed water basically satisfied the demands for toilet flush.

In order to control road runoff’s impact on adjacent water environment, this paper developed an ecological planting groove with multi-layer structure including planting soil layer, infiltration purification layer, and aquifer layer. In addition, a design method based on initial runoff purification and drainage was proposed. A series of indoor experiments with different sawdust-sand mixing volume ratio in 1:3, 1:4, 1:5 were conducted to analyze the impact of the ratio on nitrogen and phosphorus removal effect. The removal efficiency in this three ratios are 80.71%, 83.40%, 85.63% for NH₃-N; 80.13%, 83.87%, 84.38% for TN; and 92.06%, 91.03%, 88.55% for TP. Results show that optimal purification effect of different mixed packing ratio was 1:4 (sawdust: sand). Based on Erhai Lake East Ring Road, a field test showed that water quality purified by ecological planting groove is superior to the value of grade-III standard of surface water.

Green roofs are important to control peak flow and filter contaminants in LID practices. China is promoting more construction of green roofs. The enormous existing buildings in urban areas offer a fertile field to construct extensive green roofs. But inherent technical limitations exist. This paper reviewed green roof research on construction engineering, substrates, plants, energy saving, and stormwater control. The integration of extensive green roof techniques were discussed to construct such green roofs on various existing buildings. A case study in Shanghai was introduced. The trial construction and preliminary tests of the flexible module system demonstrated its potential to be promoted in Shanghai. But the reliability and further effects of the system remain to be tested in the long-term experiments.

This study was carried out to investigate the amount of evapotranspiration caused by changes in soil moisture of a retentive green roof. Two lab-scale experiments under the same conditions were conducted, with and without a retention board. An artificial rainfall simulator was used to control rainfall intensities at 20, 40, and 60 mm/h. The roof with the retention board showed the largest difference at 60 mm/h rainfall intensity. After a 10-day drying period, conventional and retentive green roofs experienced a similar amount of evapotranspiration; however, soil moisture content of the retention board was higher for the bottom layer, as it conserved water. Furthermore, unlike conventional green roofs, the retention board could prevent the transfer of heat from inside to outside in winter or outside to inside in summer, thus reducing energy consumption. Consequentially, this study shows that retentive green roofs address multiple climate change impacts, by providing relief from urban storms and reducing the impacts of extreme temperatures, thereby complementing conventional green roofs.

Selection of the xerophils and drought tolerant plants is highly crucial in green roof techniques in longer drought regions in Northwest China. In the current study, the thermal performance under natural conventional climate in summer was analyzed using the self-made simulation experiment platform through comparison of internal surface temperature with and without green roofs. Distribution frequency of internal surface temperature was investigated by dividing internal surface temperature into several ranges. Statistical analysis showed that the frequency of internal surface temperature lower than 33 °C for green roofs was 91.8%, about 1.09 times higher than that for non-green roofs, and that the sum of internal surface temperature exceeding 35 °C was about 1/3 of that for non-green roofs. The results proved that green roof has a significant insulation effect. Moreover, the thermal insulation property of green roofs had a strong positive relation with outside temperature. The thermal insulation characteristic was improved as the outdoor temperature increased.

Mountain-water-city is one of the research focuses on urban study inspired by traditional Chinese cities, aiming at relieving the contradictions between city and natural environment. However, the notion is still ambiguous since the existed research mainly focused on the conceptual framework. The methods of case study and historical study are applied to reveal the connotations of traditional mountain-water-city, while a problem-oriented comparative study is conducted to get the enlightenment from the antiquity. Changshou District of Chongqing, a small city along the Yangtze River, is selected as a typical case. Three layers of the relationship between the city and the natural environment in ancient time are analyzed, with the materials of field research and local gazetteers. Based on this, the main problems of contemporary city are analyzed in the traditional framework to propose an integrated urban planning strategy. It is declared that new-mountain-water-city could be established with the enlightenment from the ancient urban spatial form as a new pattern of city development with a low impact on the natural environment.

The urban underlying surface is key component in waterlogging control and low-impact development initiatives, including sponge cities. Using remote sensing and geographic information system data, we analyzed the relationship between natural green infrastructure (NGI) landscapes and urban submerged areas in the central urban region of Fuzhou, China. For simulations of centennial-returning storm with 2 or 4 hours of rainfall, submerged depths were 3.943 and 4.055 m, respectively. Submerged areas were characterized by high population densities and high levels of human activity. Between 2006 and 2014, NGI landscapes disappeared and were converted to impervious surfaces. Spatial association rule mining revealed a strong association between areas that were converted from NGI landscape and areas that were submerged in our simulations. Finally, we make some suggestions for sponge city planning based on our analyses of the change in urban NGI landscape patterns using ecology indices.

Low impact development (LID), as a strategy to manage urban stormwater and flood management, has brought opportunities to suitable bamboo species against the background of accelerated urbanization. In order to establish a landscape system based on bamboos’ adaptation to environmental stress and upgraded by bamboos’ landscape and eco-environmental effect, this study, based on the existing stormwater and flood management in existence, looks into the possibility that suitable species and integration of bamboos grown in Yangtze River Delta in LID practices with three perspectives of consideration: adaptability to environmental stress, landscape effect, and eco-environmental effect. This system is able to improve LID facilities not only in water resources utilization and flood control but in artistic effect and ecological efficiency, so as to shed light on LID practice and popularization.

This study reviews two reconstructed projects: Washington D.C.’s Washington Monument grounds and New York City’s Jacob K. Javits Plaza, which are significant representatives of contemporary landscape architecture planning and design outcomes. The study inspects the former, the reconstruction of a long-neglected site that happened to be at risk as a prominent and possible target of attack in the United States, and the later, surrounded by numerous civic buildings, a courthouse, and corporate headquarters. Both sites reconstructed with existing amenities, implicatively threatened by terrorist attack. Through an ex post facto evaluation, this study reassures that it is not the case that the quality of public spaces has been declining due to the heightened security and behavioral controls borne of antiterrorism, cultural, and socio-economic development concerns after the catastrophe of September 11^th, 2001. In fact, the Washington Monument grounds reconstruction came about due to city restoration, deep commitment, and long overdue repair needs, where the Jacob K. Javits Plaza has balanced protection against potential terror attack with typical landscape grading and planting skills. Both entailed intense planting and vegetation reformation without applying related green infrastructure or low impact development considerations.

The “sponge city” is becoming a hotspot with increasing urban water logging and water pollution. Based on the theory of stormwater best management practices (BMPs), Guandu District in Kunming City of China was chosen as a case study site to test the suitability and cost-effectiveness of proposed method. 56 groups of optimal cost-effectiveness solutions were selected by System for Urban Stormwater Treatment and Analysis Integration (SUSTAIN), which takes BMPs’ dimensions and the numbers of units as the decisive variables and constraints, and the reduction rate of annual runoff TN or TP load in the range of 80%~90% as the targets. Our results showed the optimized scheme to achieve the 85% reduction rate of TN or TP with the total cost of 2.116 million RMB for TN, and 1.03 million RMB for TP. In addition, green roof has less reduction efficiency of pollutant load compared to other standalone BMPs and the expansion of sunken green space in large areas should be the preferred solution to control the runoff TN or TP load in the scale of residential areas. The results give implications in rainfall control of residential area and optimum layout of BMPs scheme.

How to optimize the function of stormwater management practices is a key challenge to landscape architecture and stormwater management. This study laid particular emphasis on finding the approach to integrate stormwater management practices into landscape design, and on assessing the investment of stormwater management structural practices. Based on the four-step process of stormwater management in community park, this study compared the content including landscape hydrology, non-structural practices, management objects, and structural practices in Hillside Eco Park, China, and Crescent and Pioneer Halls, Singapore, analyzed the environmental benefits and life cycle costs (LCC) for the structural practices in those two parks. The results showed that (1) four-step process is an operational method to guide the implementation of sustainable stormwater management in community park; (2) both China and Singapore are facing the problem of making a balance between vibrant living landscape and storms; and (3) the evaluation of environment benefit and LCC is an effective way to measure the economic costs of structural practices for stormwater management, and it should be used in the planning phase for optimal design for stormwater management in community park. The methodology used in this study could be useful as a reference to consider how stormwater management can combine with landscape design in the community parks.

The restoration of polluted rivers is important to protect reservoir water sources. Heavy metal and nutrient pollutions of river selected in the Xili Reservoir Watershed were investigated with different land use and rainfall characteristics. Stormwater runoff was the main contributor of river pollution loads: Ba 68%, Pb 96%, Cr 64%, Al 60%, Fe 58%, Mn 32%, Cu 46%, Zn 78%, TN 25%, and TP 48%. Commercial land use contributed 53~80% of heavy metal loads and industrial land use was also an important source of heavy metals especially for Ba, Pb, and Cu. Nutrient loads showed different trend: commercial > residential > industrial because of eating residues generated in densely populated area. River pollution was affected by rainfall intensity and rainfall duration greatly. Strong rainfall events could wash more road deposited solids or sewer sediment into the river and the import of runoff could cause the resuspension of the river sediment. Hence, the restoration of polluted rivers should adopt comprehensive strategies of reducing the outer pollutions (e.g., stormwater runoff and sewer sediment) and cleaning the river sediment.

Rutgers University-New Brunswick, located in the state of New Jersey about one hour south of New York City, has been at the forefront in planning, designing, and implementing low-impact stormwater management measures. The university developed a stormwater and landscape management master plan and uses it as a guide during design of development projects. With a commitment to regional or campus-wide stormwater design and green infrastructure, the university has installed various stormwater features to improve water quality and reduce stormwater runoff across its four campuses including bioretention systems, wetlands, rain gardens, green roofs, and grass-covered bioswales. This paper discusses the university’s development of stormwater master plans and its commitment to regional stormwater management planning. In addition, the paper covers “lessons learned” to share insights on developing low-impact stormwater management measures that reduce maintenance costs through regional approaches and low-maintenance plantings. The paper also discusses the utilization of stormwater management measures for academic benefits.

Sponge city construction can improve cities’ ability to adapt to the environment change and the ability to cope with floods, and it can also prompt cities’ development to be more healthy and sustainable. However, the process itself of sponge city construction may also has impact on the environment especially in built-up areas, to reduce the impact, the rainwater landscape design needs to integrate sustainable thoughts as follows: (1) balancing earthwork on site. Borrowing the traditional Chinese concept of "dig lake and pile mountain", providing earthwork balance on site by adjusting the micro-topography. (2) Protecting trees and bushes on site. When introducing bio-retention ponds to the built-up area with new plants which will be drought-resistant and wet-resistant, perennial, and with low maintenance, the designers need to think about how to protect and rearrange the existing plants especially trees and bushes at the same time which are relatively stable and mature in green spaces of old town. (3) Recycling the existing paving materials. Impermeable paving material on sidewalk, square, pedestrian area, parking area, etc. will be replaced by permeable concrete, permeable bricks, gravel, other permeable materials, and waterway kerbs. These abandoned materials could be recycled on site, such as use of the old concrete slabs, bricks building short stone walls to divide space or seats for people to rest, and it will reduce a lot of construction waste and avoid the pollution of new material consummations to the environment. (4) Taking the opportunity of spongy city construction to improve urban non-motor vehicle traffic environment, raising bike lanes along roads outside blocks and small roads inside blocks with permeable asphalt to improve walking and biking environment in cities. (5) Making public open spaces such as squares and green spaces support more staying activities with the opportunity of introducing rain garden to these areas. This is a kind of sustainable urban design point of view. Following the principle of minimum energy and material consumption and reducing the impact of sponge city construction itself on the environment will avoid a new round of environmental problems and resource waste. It has important significance to the construction of ecological city.

While the sponge city construction initiative is drawing attentions and fast spreading in China, some challenges and risks remain. This research surveyed some pilot cities and identified a broad array of challenges from technical, physical, regulatory, financial to community, and institutional. The survey results show that challenges may appear in various shapes, scales, and degrees depending on geographical locations, socio-economic context, and other conditions; however, certain common themes exhibit throughout the survey results. The most dominant challenges involve uncertainties and risks. To resolve the issues, this study also identified various gateways to improve China’s sponge city construction, and recommendations are proposed including urging local governments to adopt sponge city regulations and permits to alleviate water quality and urban pluvial flooding, fully measuring and accounting of economic and environmental benefits, embracing regional flexibility and results-oriented approaches, and focusing on wider range of funding resources for sponge city construction. Coordination among other government agencies is critical, and this is true at all levels of government. Only through greater coordination, education, and broader funding could sponge city construction be advanced meaningfully and sustainably.

Assessment of overflow discharge of combined sewer overflows (CSOs) is of great importance for pollution control in combined sewer system (CSS) since in which many pollutants is often contained during the wet weather. The relationship between water level of CSOs chamber is often used to estimate the discharge. However, it is difficult to accurately estimate the overflow discharge with limit level sensors due to the complex flow condition. A computational fluid dynamics (CFD) based method which is capable to determine the most suitable location for water level sensor is presented, aiming to improve the monitoring accuracy of overflow discharge by optimizing the locations with limit sensors. The results show that the proposed method can quantitatively find the optimized location of the sensor, coupling with the global uncertainty estimation. Therefore, the proposed method can provide more accurate monitoring information for assessing the CSOs impact on receiving water bodies, rehabilitation measures, and real time control (RTC) management.

Cities are developing more outstanding and serious ecological and environmental problems. These problems are due to diverse reasons but can be traced back to the lack of regard for landforms as an important resource. Low impact development (LID) is a general plan to resolve these types of problems; LID promotes valuing landform resources and their rational use. Here, landform resources are defined, demonstrating that they are precious natural resources, and their special significance is highlighted. Incorporating a global breadth of advanced experience, planning, and design of landform resources are provided based on an urban construction case study of urban flood and waterlogged disaster prevention. LID is the key to ensuring sustainable urban development.

Green stormwater infrastructure (GSI) has been widely implemented in many cities to address the problem of stormwater runoff as well as providing a suite of other ecosystem services. The strategy and practice of adaptive design can be integrated into the GSI implementation to address multiple uncertainties by transdisciplinary collaboration, continuous monitoring, and periodic feedback: evaluation and redesign processes. In this article, we have analyzed the related theories and case studies on GSI adaptive design and summarized the principles and process to provide generally working methods to improve the performance of GSI ecosystem services.

Innovative stormwater management strategies (e.g., the low impact development, the water sensitive urban design, and the sponge city) advocate the use of rainwater harvesting systems to collect rainwater for non-potable water uses such as irrigation, washing, or toilet flushing. It not only alleviates the pressure of urban water supply but also reduces stormwater runoff which would otherwise be handled through urban stormwater management systems. Sizing the storage units is a key problem in the hydrologic design of rainwater harvesting systems. In this study, a spreadsheet based daily water balance model was developed to analyze the performances and benefits of rainwater harvesting systems with different storage unit sizes. This model considers daily rainfall data, contributing roof area, rainfall loss factors, design storage capacity, overflow, and daily rainwater demand and can be used to determine stormwater capture efficiency, tap water replacement rate, water supply reliability, benefit-cost rate, and the optimum storage capacity of a rainwater harvesting system. Daily rainfall data from 1984 to 2013 and a multi-story residential building and the lawns surrounding it in Pudong District of Shanghai was taken as an example to illustrate the application of this model. The resulting formulas and procedures may be used by engineers and municipal governments for the estimation or recommendation of suitable rainwater storage unit size.

The water quality control of urban river and lake is a critical process in low impact development. The major challenge in these pollution control projects is the uncertainty of demand, i.e., the unpredictable project period which is highly related to the construction progress of sewage systems. To meet this challenge as well as address many other problems in these projects, this research selects the rapid solid-liquid separation as the appropriate technology with the analytical hierarchy process (AHP) method and proposed a new public-private partnership (PPP) mode basing on facility leasing to facilitate the application of this technology. The risk management strategy of this mode is then analyzed. The effectiveness of the rapid solid-liquid separation technologies, as well as the leasing mode, are evaluated in a scenario analysis.