Low Impact Development Facilities Research Articles

A holistic analysis of Chinese sponge city cases by region: Using PLS-SEM models to understand key factors impacting LID performance

Sponge city is a national sustainable stormwater management program proposed by the Chinese government to deal with urban water issues (e.g., flooding, poor water quality) brought on by climate change and urbanization. Various strategies for sponge city construction are required since environmental constraints differ regionally across the country. To identify regional variations, reveal the inner links between externalities and design elements in sponge city construction, and offer practical suggestions, efforts in two directions are made based on the data of 68 sponge city cases around China: 1) discussing design parameters of four Low Impact Development (LID) facilities, including bioretention cell, permeable pavement, grass swale, and sunken green space, under four regionalization maps of hydrologic, climatic, landform and soil texture factors, and 2) building a holistic Partial Least Squares-Structural Equation Modelling (PLS-SEM) model illustrating the relationship between local characteristics, LID system design, and LID system performance in sponge city construction. The results show that: 1) rainfall and landform factors have great impact on LID facilities design, as their depths tend to be higher in water rich areas and coastal areas. 2) LID types and areas are positively influenced (+0.745) by the total area and permeable portion of a project, while the LID system performance (water quantity and quality control) is negatively impacted (−0.407) by the rainfall amount and clay fraction. 3) comprehensive LIDs choice instead of single LID facility shows more significant effect on improving LID system performance. It is recommended to establish different design standards and assessment indexing systems tailored to local environment when constructing sponge city projects.

Optimal low-impact development Facility Design in Urban Environments: A multidimensional optimization approach employing slime mould and nondominated sorting genetic algorithms

This study presents the application of the slime mould algorithm (SMA) and the nondominated sorting genetic algorithm II (NSGA-II) to optimize low-impact development (LID) strategies in urban areas. The focus is on minimizing costs and improving water quality, using three LID practices (vegetated swales, bioretention systems, and porous pavements) in combination with a drainage system. The effectiveness of this stormwater management model (SWMM)-SMA-NSGA-II model is demonstrated in Tehran, Iran, where bioretention is found to be the most successful approach for improving water quality. The results also show that the SMA outperforms the NSGA-II in optimizing cost-effective LID solutions and is more computationally efficient, potentially due to its crossover operator. This research highlights the importance of considering qualitative aspects of urban runoff management. The study demonstrates that the combination of multiple LID strategies and the use of SMA and NSGA-II have the potential to achieve optimal solutions for managing stormwater in urban areas.

Optimizing the deployment of LID facilities on a campus-scale and assessing the benefits of comprehensive control in Sponge City

Rapid and intense urbanization has brought a wide range of serious issues like flooding and water pollution, which have become a great concern in a lot of cities. In response to these problems, Sponge City (SPC) has emerged as a potential solution. This study utilized the Stormwater Management Model (SWMM) to simulate urban runoff and determine an optimal combination of Low Impact Development (LID) strategies for reconstructing the study area. Upon analyzing the existing rainwater drainage system and revealed that it could only meet the design return period of 2-years, and identified the vulnerable flood-prone area and the maximum overflow node. After comprehensive consideration of various factors, the sponge reconstruction scenario selected four LID facilities combination: Porous pavement, Rain garden, Sunken green belt, and Green roof. Results indicated that when P = 1-yr, 5-yr, 10-yr and 20-yr, the total runoff in the LID scenario decreased by 43.91 %, 43.93 %, 45.95 % and 47.11 %, respectively. LID facilities substantially mitigate stormwater runoff and peak flows during moderate to light rainfall events. These LID facilities prove effective in reducing pollutant concentrations (reduction rate is all over 42 %), with notable reductions in Chemical Oxygen Demand (COD) and Suspended Solids (SS). This paper offers valuable insights that can serve as a reference for the construction or renovation of SPC, shedding light on effective strategies and considerations for managing stormwater and mitigating the impact of urbanization.

Removal effect of pollutants from stormwater runoff in shallow bioretention system with gramineous plants.

The bioretention system is one of the most widely used low impact development (LID) facilities with efficient purification capacity for stormwater, and its planting design has been a hot spot for research at home and abroad. In this paper, ryegrass (Lolium perenne L.), bermuda (Cynodon dactylon Linn.), bahiagrass (Paspalum notatum Flugge), and green grass (Cynodon dactylon × C .transadlensis 'Tifdwarf') were chosen as plant species to construct a shallow bioretention system. The growth traits and nutrient absorption ability of four gramineous plants were analyzed. Their tolerance, enrichment, and transportation capacity were also evaluated to compare plant species and their absorptive capacity of heavy metals (Cu, Pb, and Zn). Results showed that the maximum absorption rate (Imax) ranged from 22.1 to 42.4 μg/(g·h) for P and ranged from 65.4 to 104.8 μg/(g·h) for NH4+-N; ryegrass had the strongest absorption capacity for heavy metals and the maximum removal rates of Cu, Pb, and Zn by four grasses were 78.4, 59.4, and 51.3%, respectively; the bioretention cell with ryegrass (3#) was significantly more effective in purifying than the unplanted bioretention cell (1#) during the simulated rainfall test. Overall, the system parameters were optimized to improve the technical application of gramineous plants in the bioretention system.

Optimization of LID Strategies for Urban CSO Reduction and Cost Efficiency: A Beijing Case Study

Combined sewer overflow (CSO) can lead to serious urban water environment pollution and health risks to residents. Low Impact Development (LID) facilities are one of the important measures to alleviate CSO and have been widely applied. The rational selection of LID facility types, locations, and scales is the most important task, which can effectively improve resource utilization efficiency. Based on the NSGA-II multi-objective optimization algorithm and coupled with the SWMM sewer network hydraulic model, this study takes the combined sewer overflows and the construction cost of LID facilities as optimization objectives and optimizes the types and scales of LID layout in the study area, including eight different return periods. By using the Pareto frontier and visualizing the results of the model, the effects of different rainfall return periods on the CSO control and investment cost of LID layout schemes are compared. The results show the following: (1) the optimization model can demonstrate the relationship between CSO control volume and LID construction cost under different LID layout schemes through the Pareto frontier, showing three different trends, indicating that the relationship between overflow volume and investment cost is nonlinear; (2) with the increase in rainfall intensity, higher requirements are proposed for LID schemes to meet CSO control targets, leading to a decrease in the number of Pareto frontier solution sets. Under larger rainfall intensities, it is difficult to achieve the same overflow control effect by increasing the scale of LID construction. Therefore, considering constraining the LID construction cost between RMB 5.3 and 5.38 million is helpful to determine the most suitable solution; (3) in the optimal layout schemes under different return periods, 87.3% of the locations where LID is deployed have similar scales. Based on these locations with a relatively large proportion of deployment, it can be determined that special attention should be paid to spatial positions in LID planning and construction. This study provides valuable insights for solving combined sewer overflow problems and optimizing urban drainage management and provides guidance for future planning and decision-making processes.

On the relationship between surface runoff and impervious area in the urban RPA (Receiving Pervious Area)-DIA (Disconnected Impervious Area) system: A simple equation expressing the sensitivity of runoff to changes in imperviousness

The urban RPA (Receiving Pervious Area)-DIA (Disconnected Impervious Area) system is the sub-catchment with a typical land distribution pattern where the connectivity between impervious area and drainage is disconnected by pervious area in the context of Low Impact Development (LID). The rainfall-runoff response of the RPA-DIA system is complex and plays an important role in LID management, which is not yet fully understood. In this study, to systematically learn the rainfall-runoff response of the RPA-DIA system, an indoor rainfall simulation experiment was applied to a laboratory RPA-DIA system, and an integrated surface-subsurface flow model was used to simulate the hydrological processes of actual-scale RPA-DIA systems with consideration of numerous rainfall and underlying surface conditions. Both the laboratory experiment and the numerical simulations show a segmented linear runoff-imperviousness relationship for the RPA-DIA system. A threshold of impervious area exists in the runoff-imperviousness relationship, and when the impervious area is less than the threshold, the surface runoff coefficient is zero, otherwise the surface runoff coefficient increases with impervious area in a generally linear trend. We define the slope of the linear trend as the R-I sensitivity (sensitivity of runoff to imperviousness), which is the key metric to determine the runoff-imperviousness relationship. We further explored how the R-I sensitivity changes between different rainfall and RPA conditions (e.g., different LID facilities and initial soil moistures) and found that both the laboratory experiment and the numerical simulations suggest a very simple equation to express the R-I sensitivity (RISE, Runoff-Imperviosness Sensitivity Equation) in terms of rainfall depth and intensity, including three parameters indicating the specific RPA conditions. Based on the segmented linear relationship and RISE, we have established a framework that vividly presents the rainfall control behavior of a specific RPA under different rainfall events, which can be a simple tool to provide cost-effective guidelines for LID facilities adapting to current or future rainfall characters.

Case study of optimizing Low Impact Development Strategy in School: Allocation by the Drainage Distance

Under the concept of urban stormwater management, integrated efficiency of runoff and pollutant control via low impact development facilities came into focus, whereas a few specific descriptions are provided to quantify the strategy of these facilities, including the selection patterns of the locations and sizes and the connection of LID facilities and the drainage system, which is of important for the evolvement of LID strategy. Based on the weighted multi-object goal, the optimizing LID strategy reduces of runoff, pollutant, peak flow, and flooding time under required precipitation conditions, respectively. This paper concluded LID strategy under local requirements and tougher conditions in the aspect of the size and drainage distance of each facility, a new quantified index of locations of specific types of facilities. Then interpret the adjustment pattern based on the feature of rainfalls by correlation analysis. Correlation results show that the drainage distance of green roofs and the storage tank correlated to stormwater management indicators while the retention facilities did not, and the correlation respectively weakened and stronger when storm intensity increased, helping designers to establish better LID planning for schools.

The Impact of Non-Point Source (NPS) Management on Non-Point Source Reduction and Water Cycle Improvement in an Urban Area

Suwon, the capital and largest city of Gyeonggi-do, South Korea, was designated as a non-point source management area in 2010. The management period ended in 2020, so follow-up measures are needed. In this study, we investigated several projects implemented in Suwon for urban water cycle improvement and non-point source pollution reduction, and the long-term management effects were analyzed to suggest policy directions such as the revision of designation notices. During the 10-year management period in Suwon, the population and lot area continued to increase, and the non-point source-based annual Biochemical Oxygen Demand (BOD) discharge loads also increased by approximately 25% at the half sub-basins Hwangguji-cheon and Woncheonri-cheon in 2020 compared to 2010. Even under these conditions, statistical analyses show that the Biochemical Oxygen Demand (BOD) and Total Phosphorus (TP) concentrations monitored at the outlet of basin were decreased due to the promotion of a large-scale sewer management project as well as non-point source pollution reduction projects. Also, the field monitoring data-based Load Duration Curve (LDC) analysis results indicate that the loads decreased in the high-flow period of 2020 compared to 2015. Also, the Normalized Difference Vegetation Index (NDVI) values calculated using satellite images since 2017 tended to increase slightly during the period when the impervious area estimated using the land registration map increased. It is assumed that using the current calculation method for impervious areas has limitations regarding its ability to reflect changes in the small-scale Low-Impact Development (LID) facility and in ecological/landscape areas. On the other hand, the annual variation in direct runoff estimated at the outlet using three hydrograph separation methods did not show any improvement with regard to storm water retention during the management period. These results reveal that the effects on urban water cycle improvement, such as peak flow reduction and base flow increase, may not be noticeable despite some progress in reducing non-point source pollution and increasing green area. Therefore, additional efforts directed towards non-point source pollution management focused on water cycle improvement are required in the city, especially in the sub-basins with higher pollution loads such as Hwangguji-cheon and Seoho-cheon.

Comparative Analysis of Flood Prevention and Control at LID Facilities with Runoff and Flooding as Control Objectives Based on InfoWorks ICM

Climate change and urbanization have led to an increase in the amount of water flowing into traditional drainage systems, which results in frequent urban flooding. Low–Impact Development (LID) facilities, with their distributed feature, are one of the important means to mitigate flooding and have been widely used. In this paper, based on integrated catchment management (ICM), we compare the abatement of runoff, flooding, and ponding under two durations of rainfall and eight different return periods with runoff as the control objective (RACO) and flooding as the control objective (FACO) for the deployment of LID facilities. The waterlogged area of FACO is higher by a range of 92.462 m2 to 24,124.39 m2 compared to RACO. Both percentage reduction of overflow volume and runoff volume tend to decrease gradually with the increase in the return period. For the percentage reduction of runoff volume per unit area, sometimes RACO is greater than FACO, and sometimes vice versa, while for the percentage reduction of overflow volume per unit area, the range where FACO exceeds RACO is between 0.29 to 10.95 (%/ha). The cost of FACO has decreased by 4.94% to 46.20% compared to RACO. This shows that FACO’s LID deployment method can fully utilize the capacity of LID facilities to mitigate inundation, reducing the cost of LID facilities to a certain extent.

Waterlogging Prevention and Control Planning Based on the Concept of Sponge City - A Case Study of Kirin Science and Technology City

With the accelerated development of urbanisation, the problem of waterlogging is increasingly becoming a serious challenge for cities. In order to effectively deal with the risk of waterlogging, this study proposes a set of waterlogging prevention and control planning based on the concept of sponge city construction. It focuses on giving full play to the water reduction effect of Low Impact Development (LID) facilities through the integrated application of ecological emission reduction systems and drainage and risk removal technologies to reduce rainwater runoff and improve the city’s flooding resilience. The method is applied to Kirin Science and Technology City as an example, and the results show that the total annual runoff control rate, the water surface rate, and the water surface storage capacity of this area are all significantly improved, which can provide a reference for deepening the scientific understanding of the mechanism of urban rainfall and flood formation and adopting effective management means.

Stormwater Runoff Control and Water Resource Utilization Technology of Central China Normal University Based on Stormwater Flood Management Modeling

In recent years, more and more prominent urban flooding problems on campus drainage system planning and design put forward higher requirements. Sudden rainfall can have multiple negative impacts on campuses, but it is also an excellent opportunity to utilize rainwater resources. At present, the peak flow rate of urban drainage system in China is still mainly calculated by the inference formula method, and the design return period of municipal drainage system is also low, which may lead to campus flooding in case of large rainstorms. In this paper, using the Stormwater Flood Management Model (SWMM) as a platform, the Central China Normal University (CCNU) was selected to simulate the summer stormwater runoff process, and three different combinations of low-impact development (LID) facilities were applied to the campus stormwater runoff control, and the control effects of the different combinations on the flood peak flow abatement were compared. The results show that the selected LID deployment scheme is better than the single facility control effect. Finally, based on the results of the study, a technical solution for rainwater collection and reuse based on sponge campus was proposed to renovate and design the campus landscape of Central China Normal University. The economic, social and environmental benefits are significant and can provide a reference for rainwater collection on other campuses.

Cost-effectiveness Analysis in Low Impact Development of Qinxin District, Qingyuan City, Guangdong China

In recent years, thanks to extreme weather like storms and downpours, flood events have occurred frequently worldwide, endangering the personal and property safety of citizens. Most developed regions use low impact development (LID) measures to prevent flooding and other water-caused disasters. However, the laying cost of LID is expensive, and the utility of LID is different based on different types of LID facilities. Given the flood news in the Qingxin District of Qingyuan City, which caused plenty of citizen lives and property losses, it is necessary and urgent to study the drainage system plan and construction in this place in order to prevent another blow from bad weather in the future. Therefore, this paper aims to study the cost-effectiveness of various types of LID by the precipitation data of Qingyuan so as to find out how to reduce flood inundation at the lowest cost. The results demonstrate that the covered area of vegetative swale is simply 600m^2, and it can reduce most runoff and outflow. Besides, multiple LIDs can reduce nearly 40% of runoff and overflow in the most significant gap. Based on the reliable simulation analysis and former research, it can be concluded that the vegetative swale is the most cost-effective facility toward other LIDs, and the permeable pavement is the worst efficiency measure.

Distribution of microplastics in rainfall and their control by a permeable pavement in low-impact development facility

Microplastics (MPs) released from plastic products in daily life are present in the air and could be transported to freshwater environments along with rain. Recently, low-impact development (LID) facilities, such as permeable pavements, have been used to treat non-point source pollutants, including rainfall runoff. While runoff is treated by LID facilities, the periodic monitoring of MPs in rainfall and the efficiency of removal of MPs through LID facilities have rarely been investigated. Therefore, this case study focused on monitoring MPs in rainwater runoff and permeate from a permeable pavement in Busan, South Korea, thus evaluating the removal efficiency of MPs by a LID system. The initial rainfall runoff and permeate through the LID system were sampled, and the amounts, types, sizes, and shapes of MPs in the samples were analyzed using micro-Fourier Transform Infrared (FTIR) spectroscopy. The results showed that the distribution of MPs in the initial rainfall was affected by population in tested area. Polyethylene was the most common type of MPs in all the samples. Polyamide was only found in the LID samples because of the pollution caused by water flows and pavement materials. Fragment type MPs was most commonly observed and consisted of relatively small-sized (under 100 μm) particles. LID facilities were able to capture approximately 98% of MPs in the rainfall through a filtration process in the permeable pavement.

Study on Calculating Appropriate Impact Assessment for LID Facility Using A-I-R Curve

Low impact development (LID) facilities are designed to maintain water circulation functions on the surface and subsurface. LID facilities can be applied to various areas and are expected to have both short-term and long-term effects, making them widely installed in urban areas. In this study, our objective is to calculate the A-I-R (Area ratio-rainfall Intensity-Runoff reduction rate) curve by applying design standards to tree filter boxes, garden plant pots, infiltration ditches, and rain barrels among various LID facilities. The analysis was conducted by constructing a SWMM-LID model and analyzing 209 items, considering the area ratio (A) and rainfall intensity (I) of the LID facilities. The runoff reduction rate (R) varies by LID facility according to the A-I-R curve. It reaches up to 100.0% for rain barrels, up to 30.0% for infiltration ditches, up to 20.0% for garden plant pot, and up to 12.0% for tree filter boxes. If the A-I-R curve of the LID facility is applied to the design standards, it is expected to facilitate the design of the facility’s size and inlet according to the target reduction rate.

Public preferences and willingness to pay for low impact development: a comparative case study of pilot sponge cities in China

Abstract Increased urbanization and climate change globally have increased the frequency of extreme weather, especially rainstorms and flooding. Low impact development (LID) has been adopted for several decades to reduce urban pluvial flooding and cope with urban climate change. However, LID hasn't been widely used due to the lack of sustainable funding. In this article, a discrete choice experiment method was used to understand public preferences and willingness to pay (WTP) for the functions of LID facilities. Four attributes were selected, and after that, 958 and 646 valid questionnaires were collected in the pilot sponge cities of Zhengzhou and Hebi, respectively. The results showed that respondents showed a significant WTP for LID facilities, with a desire to support rainwater drainage, recreation and entertainment, and the landscape environment. Experience of flooding had a significant effect on Zhengzhou respondents, but not on Hebi respondents. We have concluded that rainwater drainage should still be considered the most important function of LID facilities. At the same time, educational level and flood experiences may not affect the public's WTP. This article can provide a reference for cities that would like to implement LID and create a stormwater fee system to adapt to global change.

Optimization of the Low-Impact Development Facility Area Based on a Surrogate Model

Optimization of the Low-Impact Development Facility Area Based on a Surrogate Model

Maintenance of low impact development facilities: A case study of pilot sponge cities in China

The concept low impact development (LID) has been provided for over five decades for achieving sustainable stormwater management. However, once installed, LID facilities often suffer from a lack of maintenance, resulting in impaired functionality and substantial wastage of financial resource. Since 2014, many LID facilities have been constructed in Chinese pilot sponge cities. However, to date, there is little knowledge about the post-construction status of these LID facilities. In response, we investigated the current status quo, common problems needing maintenance, and residents’ attitudes towards maintenance of LID facilities. The results showed that, among 467 bio-retention facilities in three surveyed pilot sponge cities, approximately one third of the bio-retention facilities were in a good state; However, more than one thirds are facing issues of decreasing vegetation coverage rate, a deteriorating vegetation growth situation, and the slight silting or blocking of water inlets or overflow ports. Thus, regular maintenance is necessary, but the starting maintenance time can go through in the fifth year after construction. Unfortunately, public participation on the maintenance would be difficult. Even those respondents who willing to pay for the maintenance fee or possessing previous knowledge exhibit reluctance to engage in maintenance practices. The paper provides decision makers with a comprehensive overview of the status quo and common maintenance problems associated with LID facilities in the Chinese pilot sponge cities. It can also equip governments with insights to effectively address maintenance and management issues related to LID facilities.

Comprehensive effect evaluation of LID facilities implemented in sponge campuses: A case study

A sponge campus is a campus implemented with Low Impact Development (LID) facilities aimed to improve its urban resilience and stability against the effects of climate change by enhancing storm water management. In this study, a secondary school campus was designed and transformed into sponge campus by installing LID facilities, and we found it of high runoff control effect and energy conservation potential. Using the Storm Water Management Model (SWMM), this study assessed the performance of the LID facilities under different rainfall intensities with recurrence periods of 1, 5, 10, and 20 years. The SWMM modelling revealed that the peak flow was reduced 59.1%, 54.5%, 47.9% and 46.8%, respectively, while the total inflow was reduced 33.9%, 28.0%, 25.4% and 24.6%, respectively. The sponge campus achieved a total suspended solids (TSS) removal of 75%. Specifically, this sponge campus accounted for 9.2% of the plot area while contributed 15.1% water storage capacity to the neighbouring region (recurrence period 1a). Furthermore, the implementation of LID facilities on the school campus could help conserve 17,524 kW·h of electricity annually. Overall, this study provides useful insights and guidance for the construction of sponge campuses.

Development of a Simple Design Method for an Infiltration Facility using Curve Number

As climate change accelerates, the scale and intensity of natural disasters are increasing, and the frequency of localized heavy rains is increasing rapidly. Urban watersheds have a high ratio of impervious areas. So there is a high possibility of flooding in the event of torrential rain, and large-scale damage can occur because the population and material resources are highly concentrated. River improvements, sewerage maintenance, and rainwater storage installations are frequently used to reduce flood damage. More recently, low-impact development (LID) techniques have been proposed; however, LID facilities are installed on a small scale and in various locations. In addition, they require many parameters for a rainfall-runoff analysis; consequently, the design of these facilities require too much manpower and time. In this study, we analyze the rainfall-runoff reduction effect based on the size of a facility to present a simpler, more efficient design method. Next, the curve number (CN) corresponding to the capacity of each facility is estimated and the correlation between the facility’s area ratio and the CN is analyzed. As a result, a relational expression that can calculate the new CN with the same rainfall-runoff reduction effect as the installed LID facility was derived by using the CN before the installation of the LID facility and the facility area ratio. Thus, we present a simple design method using the recalculated CN without directly entering LID facilities into a storm water management model (SWMM).

Comparisons of Retention and Lag Characteristics of Rainfall–Runoff under Different Rainfall Scenarios in Low-Impact Development Combination: A Case Study in Lingang New City, Shanghai

An increasing focus has been given to stormwater management using low-impact development (LID), which is regarded as a “near-nature” concept and is utilized to manage and reduce surface runoff during the rainfall–runoff process. According to the hydrological monitoring data, we evaluated the retention and lag characteristics of rainfall–runoff in LID combination under three rainfall-intensity scenarios (light–moderate, heavy, and torrential rainfall) in Lingang New City in Shanghai. LID facilities have been constructed for three years in the target study area, including rain gardens, retention ponds, green parking, porous pavement, and grass swales. The average runoff retention was 10.6 mm, 21.3 mm, and 41.6 mm under light–moderate, heavy, and torrential rainfall scenarios, respectively, and the corresponding runoff retention rate was 72.9%, 64.7%, and 76.1% during the study period. By comparing rainfall, runoff retention, runoff retention rate, cumulative rainfall, and lag times, it becomes evident that the ability to retain runoff can be greatly improved in the LID combination. The average runoff retention was significantly enhanced by nearly two times and four times under the heavy and torrential rainfall scenarios compared to the conditions under the light–moderate rainfall scenario. Furthermore, the lag time from the end of rainfall to the end of runoff (t2) and the lag time between the centroid of rainfall and the centroid of runoff (t3) showed a significantly negative correlation with rainfall intensity. Meanwhile, t3 presented an incredibly positive correlation with rainfall duration. In this study, the LID combination demonstrated superior benefits in extending the duration of runoff in rainfall events with lower rainfall amounts, and demonstrated significant overall lag effects in rainfall events with longer durations and lower rainfall amounts. These results confirmed the vital role of the LID combination in stormwater management and the hydrologic impact of the LID combination on rainfall-induced runoff retention and lag effects. This work has provided valuable insights into utilizing LID facilities and can contribute to a better understanding of how runoff retention and lag characteristics respond to different rainfall intensity scenarios.