Low Impact Development Facilities Research Articles

Effects of Low-Impact Development Facilities (Water Systems of the Park) on Stormwater Runoff in Shallow Mountainous Areas Based on Dual-Model (SWMM and MIKE21) Simulations.

Rapid urbanization has triggered more serious urban flood risks. Many studies have focused on intra-urban flooding, but less attention has been paid to rainfall and flood risks at the urban fringe. Nowadays, China is vigorously promoting the construction of sponge cities in the whole area. It is important to study the construction of sponge cities in shallow mountainous areas, which are an important barrier between cities and mountains. The purpose of this paper is to investigate the performance of Low-Impact Development (LID) facilities under different rainfall scenarios in developed shallow mountainous areas. The second garden and flower exposition ("the Expo Park") in Hebei Province is used as an example. The SWMM and MIKE21 models were used to simulate the hydrological processes before and after the construction of "the Expo Park", and the models were calibrated with the measured data. Peak flow rate, outflow volume, rainfall-outflow ratio, runoff velocity, and water feature area of the water system were used as indicators to evaluate their effectiveness. The results showed that the placement of LID facilities had a positive impact on the construction of the shallow mountain area. Specifically, (1) LID facilities can reduce the peak flow rate, delayed peak flow time, outflow volume, and rainfall outflow ratio of stormwater runoff in mountainous areas; and (2) they can effectively collect rainwater and become a supplement to the landscape water system of the site. These findings provide a scientific basis for the construction of LID facilities in shallow mountainous areas, which is important for the development and flood management of shallow mountainous areas.

Simultaneous degradation of sulfadiazine and dissolved organic matter based on low‐impact development facilities

Sulfadiazine (SD) is a common antibiotic administered to treat bacterial infections in livestock, and its fate and migration are greatly affected by dissolved organic matter (DOM). The soil infiltration system [a typical low-impact development (LID) facility] can significantly alter DOM properties during runoff pollution, thus affecting the complexation of SD with DOM. Here, the binding characteristics of different DOM components and SD in the soil infiltration system were explored using spectroscopic techniques (excitation–emission matrices, parallel factor analysis, and synchronous fluorescence spectroscopy). Combined with the weakening of DOM fluorescence intensity and 78.63% reduction in mean SD concentration following treatment, synchronous degradation may have occurred. The binding sequence of SD and DOM fluorophores was further explored using two-dimensional correlation spectroscopy. Effluent DOM showed greater sensitivity to SD and more binding sites than influent DOM. Moreover, hydrophobic protein-like substances exhibited higher log KM values than other fluorescent components, indicating that protein-like components play significant roles in SD complexation. The soil percolation system improved the complexation stability and binding sequence of fulvic-like substances. Thus, SD–DOM can be intercepted and degraded using LID facilities to reduce the risk of SD in aquatic environments.

Effect of sponge city construction on urban waterlogging reduction in semi-humid areas of China

Abstract Urban waterlogging frequently occurs in semi-humid areas due to the short duration of heavy rainfall in summer and the high rates of subsurface hardening caused by high-intensity urban development. To solve the problem of urban waterlogging, China has launched the construction of ‘sponge cities’ and made some progress, but there is still a lack of comprehensive consideration of the functional types and spatial layout of low impact development (LID) facilities. Qian'an, a city of Hebei Province, is one of the first sponge city pilot cities in China. This paper focuses on Yanshan South Road and its surrounding areas, a historical waterlogging section of Qian'an city. Four common LID measures (sunken green space (SG), bioretention ponds (BP), infiltration ponds (IP), and reservoirs (RE)) in two function types are selected and combined through centralized (CE) and decentralized (DE) different spatial layouts, a total of 80 design scenarios are proposed. Then, using the storm water management model (SWMM) to calculate the effect of each scheme on peak flow reduction under different rainfall return periods. The results showed that all LID scenarios can effectively alleviate the urban waterlogging problem, among which the schemes of DE-SG-BP (1:1), DE-IP-SG (1:1), DE-SG-IP (3:1), DE-SG-IP (1:3), and DE-SG-BP (3:1) had the highest peak flow reduction rate, up to 95.46%. The schemes of CE-RE-IP (3:1) and CE-IP-RE (3:1) had better hydrological performance in occupying less surface space, with a peak flow reduction rate of 8.68% per square meter. Therefore, the distributed layout combined with infiltration LID facilities and storage LID facilities can be used in urban built-up areas with limited land use conditions, which has a more obvious effect on reducing waterlogging.

The Multi-Objective Optimization of Low-Impact Development Facilities in Shallow Mountainous Areas Using Genetic Algorithms

From the perspective of whole-area sponge city construction, it is important to scientifically determine the layout plan of LID facilities for controlling urban rainfall and flooding problems, given the topographical features and rainfall runoff characteristics of shallow urban mountainous areas. Current research on the optimization of low-impact development facilities is limited to the central urban area level, with insufficient research on shallow urban mountainous areas, and there is great uncertainty in the layout of LID facilities when multiple objectives are considered. Therefore, this paper applied a genetic algorithm (NSGA-II) to optimize the layout scheme of LID facilities. Multiple objectives of the peak runoff abatement rate, cost, and land area were selected as the optimization objectives, and the optimized results were ranked using the EWM-TOPSIS and VCWM-TOPSIS methods. The 2nd Hebei Provincial Garden Flower Expo (Qinhuangdao) Park was used as the research object for the optimization design. The results showed that, under the premise of water safety, the lowest cost priority was given to the LID facility with a 15.49% share, 99.43% peak runoff reduction rate, and a cost of CNY 1.215 × 107; the lowest area priority was given to the LID facility with a 15.25% share, 99.42% peak runoff reduction rate, and a cost of CNY 1.267 × 107. The EWM-TOPSIS method was also used to obtain the best optimized solution with 16.18% LID facilities, 99.64% peak runoff abatement rate, and a cost of CNY 1.26 × 107, and the worst optimized solution with 12.55% LID facilities, 97.91% peak runoff abatement rate, and a cost of CNY 1.061 × 107. The decision results under different decision-maker preferences were obtained by the VCWM-TOPSIS method. This study showed that the combination of a genetic algorithm and TOPSIS can optimize the layout of LID facilities in shallow mountainous areas more scientifically and efficiently compared to the actual construction plan for building a sponge city.

Analyzing the Impacts of Sewer Type and Spatial Distribution of LID Facilities on Urban Runoff and Non-Point Source Pollution Using the Storm Water Management Model (SWMM)

The negative changes in the hydrological cycle are increasing due to climate change and urbanization, resulting in deterioration of water quality and environmental issues. Although Low-Impact Development (LID) techniques studies have been conducted to solve this problem, the spatial distribution of LID facilities and sewer types has received less attention. In this study, it is proposed to analyze the effects of sewer type, the spatial distribution of LID facilities, and LID type on runoff and water quality using the Storm Water Management Model and to identify effective ways of improving the hydrological cycle and Non-Point Source (NPS) pollution associated with urbanization. As a result of the runoff reduction analysis, 68% of the rainfall was discharged at the outlet for separate sewers, 79% for combined sewers without storage tank, and 49% for combined sewers with storage tank. The LID scenario results showed the distributed LID application method has higher reduction efficiency of runoff and NPS pollution than the intensive application method. Moreover, intensive application of LID in downstream areas resulted in higher runoff reduction efficiency than the application of LID in upstream areas. It will be used not only in the hydrological cycle plan but also in NPS pollution management.

The hydrological effect and uncertainty assessment by runoff indicators based on SWMM for various LID facilities

Low Impact Development (LID) facilities are the key to realizing the source control of stormwater. However, there are few studies on the control effects of different LID facilities on runoff volume and runoff quality. In this paper, based on the Storm Water Management Model (SWMM), a Monte Carlo method was used to simulate the runoff process for five LID facilities. The correlation analysis and scoring of the three indicators of runoff coefficient, peak runoff, and Suspended Solid (SS) wash-off in the simulation results were conducted to evaluate the control effects of different LID facilities. The simulation results showed an evident law of decreasing marginal effect in the deployed area of LID facilities. In addition, the uncertainty of the hydrological response of permeable pavement is the smallest among the five types of LID facilities, and the uncertainty of vegetative swales is the largest. Under the suitable combination of parameters, the area percentage of permeable pavement reaching the upper limit of the control effect of three indicators is the smallest; the control effect of three indicators of infiltration trench is the best. Correlation analysis showed that the three indicators of the LID facilities could be estimated from each other through the regression relationship equation.

Cost-Effectiveness Analysis of a Sponge City Construction Based on the Life Cycle Cost Theory—A Case Study of the Yanshan South Road Area of Qian’an City, China

In semi-humid regions of China, annual precipitation is not evenly distributed. Heavy, summertime rainfall with a short duration frequently causes urban flooding, and annual rainfall less than evaporation results in urban water scarcity. In 2014, Hebei Province’s Qian’an city was ranked among the first group of sponge city pilot cities. This paper investigates the historically flooded section of Yanshan South Road and its surrounding area in Qian’an, focusing on the cost of resolving an urban water problem. Using the storm flood management model (SWMM) and the life cycle cost (LCC) method, the waterlogging reduction effect and life-cycle cost of various low impact development (LID) scenarios were evaluated. Six rainfall design scenarios were simulated and calculated so that the hydrological performance and cost-effectiveness could be comprehensively evaluated to establish the economic value and effectiveness of implementing LID facilities. This study found that the cost-effectiveness values of sunken green space (SG), SG + infiltration ponds (IP) (3:1), SG + IP (1:1), and SG + IP (1:3) scenarios for infiltration LID schemes were relatively high, up to 2.10. In the infiltration-storage LID scheme, the cost-effectiveness of the SG + reservoirs (RE) (1:1) was grater, which was 1.84. In semi-humid regions, the regulation and storage of rainwater, regarding its collection and use, can be widely applied to the construction of sponge cities.

Responses of urban flood processes to local land use using a high-resolution numeric model

Rapid increase of urban impervious surface, resulting from unplanned urban sprawl, leads to the frequent occurrence of urban flood disasters caused by abnormal precipitation in flood season. In this work, a coupled urban rain flood model and normal pipe network model is employed to simulate the city inundation and pipe network hydrodynamics under different local land use types. The results shows that the peak surface inundation and pipe network outlet flow after transformation were 4.36%–42.43% and 0.01%–1.34% higher than those before transformation for P ≤ 20, and its corresponding values reached 1.24%–5.59% and 27.26%–35.21% for P > 20. The change in land use types in local areas significantly impacted inundation of the whole surface under normal rainfall (P < 20), which was also verified by the water recession coefficient. In addition, land use transformation slightly affected urban inundation for P ≥ 100, which indicates that low-impact development facilities were almost ineffective in addressing inundation under extreme rainfall. A significant impact on the pipe network discharge was observed under the high rainfall return period (P ≥ 20). The recession coefficient obtained via coupled model simulations can be effectively applied in the urban flood recession process.

Runoff Reduction Effects at Installation of LID Facilities under Different Climate Change Scenarios

In order to prepare for floods and droughts that occur as a result of climate change, various studies in water-related fields are being carried out in various countries around the world. Among them, special attention is being paid to the low-impact development (LID) technique. This study measured the annual maximum daily rainfall data from 2019 to 2100 by climate change scenario, which is the annual maximum daily rainfall series observed for rainfall stations, and tested the hydrological data using statistical analysis. After determining whether the data could be analyzed, the probability distribution was selected, and the parameters of the selected probability distribution were calculated using the L-moment method for each rainfall station. The probabilities of rainfall data were derived using GEV distribution, and the United States Environmental Protection Agency Storm Water Management Model (SWMM), a runoff simulation program, was used to compare and analyze the runoff reduction rate before and after the installation of a permeable pavement as an LID facility. The results of the analysis showed that representative concentration pathway (RCP) 4.5 and RCP 8.5 had the effect of reducing the runoff for more than 100 years at a 30% reduction rate compared with before installation.

Structural changes and denitrification performance evaluation of bioretention cells with collapsible loess modified by coal gangue

Bioretention cells are considered to be promising low-impact development facilities and are widely used in urban areas. Common bioretention cells are filled with planting soil, gravel, and sand. In collapsible loess areas, gravel and sand are expensive and difficult to obtain. However, the abundant loess in these regions can be used to build bioretention cells. Collapsible loess has excellent adsorption and water retention properties and is suitable for use as filling in bioretention cells. Because the collapsibility of this soil type leads to poor water permeability, it is necessary to modify the collapsible loess used as bioretention cell filler. Modification with coal gangue can significantly improve the permeability coefficient of collapsible loess and reduce its settlement, allowing modified loess filling to meet the parameter requirements for bioretention cells. This experiment shows that when the volume ratio of collapsible loess to coal gangue was less than 2:1, the permeability coefficient was greater than 1.35 cm/h. Variations in the pollutant removal effect under varying initial filler water content were studied using columns that met the parameter requirements. It was found that the removal efficiencies of ammonia-nitrogen (NH4–N), nitrate-nitrogen (NO3–N), and total nitrogen (TN) in the experimental columns were as high as 98%, 97%, and 98%, respectively. When the proportion of collapsible loess in the filler was higher, the column was more likely to recover its pollutant removal capacity after new rainfall events. The results show that the initial water content of the filler before each rainfall event had a significant influence on the pollutant removal efficiency. When the initial moisture content was lower than 40%, a large number of pollutants were leached from the bioretention cell during the early stage of water inflow, and the recovery time was long. Therefore, maintaining bioretention cells during dry periods is very important for their performance.

Effect of surface area to catchment area ratio on pollutant removal efficiency in vegetation-type facilities

In Korea, non-point source emissions have been investigated since the early 1980s, and the proportion of non-point source sources as a source unit for each land use has been evaluated based on actual measurement data following the implementation of the Total Water Pollution Control System. Recently, a lot of research has been done on the application of LID(low impact development) technology that can effectively manage nonpoint pollution and rainfall runoff. The ratio SA/CA (surface area/catchment area) is one of the design factors for LID facilities. In this study, the major objective is to analyse relationship between the SA/CA ratio and efficiencies of runoff reduction and pollutant removal. To do this, long-term monitoring has been conducted for three - years at LID facilities installed at a domestic LID pilot project complex. The type of LID facilities analyzed in this study are grassed swale, vegetative filter strip, tree filter box, planter box, and bioretention. As a result of logarithmic relation analysis, efficiencies of pollutants removal tended to increase with increasing SA/CA ratio. Among the pollutants, TP(total phosphorus) had the highest correlation with R value of 0.9365. When SA/CA is under consideration as a design factor, this research data can be used as input for the designer for calculating the specific criteria and scope.

Retention and lag effects of rainfall runoff in a low impact development area

In view of the insufficient quantitative analysis of lag effect of rainfall runoff in low impact development (LID) areas in the construction of sponge city, we evaluate the retention and lag effects of runoff of three combinations of LID facilities including Parking lot-Rain garden, Roof-Elevated bioretention-Permeable pavement-Grass ditch, Roof-Elevated bioretention-Permeable pavement-Grass ditch-Rain garden in Shenzhen Makan Environmental Protection Industrial Park based on the observation data in 190 rainfall events, and comprehensively analyze the influences of rainfall characteristics and combination of LID facilities on the effects. The results show that LID facilities can retain 75.0%-86.5% of rainfall, and LID can retain 2.2-9.9 mm of accumulated rainfall before runoff generation. Compared with the rainfall process, the end time, centroid position and peak position of runoff in LID combinations lag 100-115 min, 30-68 min and 13-34 min, respectively. The series connection of LID facilities can help to improve the lag effect of runoff. With the increase of drought time before rain, the LID combinations accumulate more rainfall before yielding runoff. With the increase of rainfall amount or rainfall duration, the lag effects of runoff end and centroid position increase. While the lag effect of peak position increases with the decrease of rainfall intensity and the advance of rainfall peak. The results are helpful to strengthen the understanding of the lag effect of LID on rainfall runoff.

The effect of low impact development facilities on evapotranspiration in an outdoor space of urban buildings

Low impact development (LID) facilities have been regarded to have important regulatory effects on urban evapotranspiration (ET). However, due to the influences of heterogeneity of underlying surfaces or facilities, solar radiation, building shading and rainfall conditions, the ET variations in outdoor space of urban buildings (OSUB) with various LID facilities are complex and have not been reported. In this paper, a three-temperature model (so called 3T model) combining with a portable thermal infrared imaging sensor was used to in-situ measure the ET rates of different LID facilities and traditional underlying surfaces of an OSUB in 2019 in Shenzhen, China. Specifically, the seasonal, daily and diurnal variations of ET in the OSUB and their influencing factors were investigated. The results indicate that (1) the LID facilities have higher ET rates than the traditional surfaces in wet seasons; the ET rates of bioretention (BR-H), vegetated swale (VS-Z) and permeable concrete pavement (PCP) are 38%, 18% and 250% higher than those of traditional garden (TG-H), lawn (TL-Z) and impermeable brick pavement (IBP), respectively, in this study; (2) the diurnal variation of ET is greatly affected by solar radiation intensity, building shadow and moisture inside the LID facilities; and the ET increase by LID is higher in the OSUB with higher solar radiation and no shadow; (3) vegetated LID facilities (e.g., BR-H and VS-Z) can maintain at a relatively high ET rate for a longer period after rain than the non-vegetated LID facilities (e.g., PCP), indicating a stronger ability to increase urban ET; (4) when the proportion of LID in OSUBs increases from 0% to 50% and 100%, the ET rate of OSUBs increases by 28% and 51% respectively, and the annual ET of built-up areas in Shenzhen increases by 6.58 mm and 11.41 mm respectively. The effects of soil media, vegetative cover, LID facility structure, local climate and building shadow on the ET of OSUBs should be considered for extrapolating the site-scale study to urban or catchment scale.

The optimization of Low Impact Development placement considering life cycle cost using Genetic Algorithm

Low Impact Development (LID) is an effective measure in controlling the urban runoff and mitigating the non-point source pollution. The determination of LID facilities and layouts for a sub-catchment is important for designing stormwater management system. However, there are remain large uncertainty and challenge exist in determination of LID facilities when consider budget, land use, soil surface and groundwater as well as local climate etc. To address this issue, this study employed Genetic Algorithm (GA) for optimization of the selection and layout of LID. The urban runoff was simulated using Environmental Protection Agency (EPA) Storm Water Management Model (SWMM). The LID planning was encoded as 0 and 1 in GA algorithm. The multiple objectives which include runoff reduction, area of LID and life cycle cost were selected as optimization targets. To test the model performance, the Airport Economic Zone in Tianjin, China was chosen as the study area. The results demonstrate that the combination of LID approaches are most effective measures on runoff reduction through long-term simulation (10 years' rainfall events). The impact of different weights of land area and cost on LID selection were evaluated when considering life cycle cost. Bio-Retention is preferred when considering the area of LID and Green Roof is recommended when the cost is prioritized. The present research proved GA is feasible for LID planning in urban area. The proposed method can help the decision-makers to determine the LID plan more scientific based on SWMM model and GA.

Comprehensive Optimization Framework for Low Impact Development Facility Layout Design with Cost–Benefit Analysis: A Case Study in Shenzhen City, China

Sustainable storm water management benefits a lot from low impact development (LID). The early-stage design of LID layout is critical for LID practices. However, the technology gaps still exist for an accurate, flexible, and systematic solution of optimal design. Literature works usually only consider the size and number of LID facilities in a given scenario or even totally empirical, which lacks integration of facility selection, connection, and size with multiple management objectives together. Therefore, this study proposed a generic and comprehensive framework for LID layout design with cost–benefit analysis. Powered by the computer coding scheme for the LID layout and a hybrid optimization algorithm, the framework was successfully verified in Sponge City of Shenzhen, China. The optimization results of genetic algorithm proved the stability of the novel coding scheme for LID layout. The best and worst scenarios are selected from the Pareto front through the entropy weight method. The variable cost weight method revealed the sensitivity from the cost preference of the decision maker. High construction costs and environmental effectiveness can be scientifically balanced in the procedure of early-stage design. The proposed design framework is expected to be widely verified and applied in storm water management practices around the world.

Effects of rainwater infiltration in low impact development facilities on adjacent municipal roads in collapsible loess

The effective and reasonable construction of the low impact development (LID) facilities in loess area depends on the functionality of typical LID facilities and the safety of surrounding structures in areas. A full-scale field test on rainwater-concentrated infiltration of bioretentions in a collapsible loess site was conducted in this study. The water content and deformation law of the site were analyzed, and the water movement law of the rainwater-concentrated infiltration at bioretention facilities in the loess site was determined. The site settlements were calculated as per the wetting deformation curve and infiltration depths were calculated on an improved infiltration depth model tailored to the loess area. The rainwater infiltration rules of different bioretention structural forms are different in the collapsible loess field. The diffusion rate of the retaining wall type in loess decreases over time, while that on a sloping type does not. Within the same infiltration time, the retaining wall has a stronger influence on the site than the sloping type. When the water is concentrated in the site, its influence on the subgrade settlement is small (generally less than 1.5 mm) enough to satisfy the relevant engineering requirements. Facilities water infiltration laws in the site can be predicted using the fractional unsaturated infiltration model and a modified Green-Ampt model based on assumed loess saturated–unsaturated stratification. The adverse effects of water infiltration related to stagnant bioretentions can be mitigated by adjusting the initial water content and saturated water content at the loess site.

The Application of Low Impact Development Facility Chain on Storm Rainfall Control: A Case Study in Shenzhen, China

In recent decades, low impact development (LID) has become an increasingly important concern as a state-of-the-art stormwater management mode to treat urban flood, preferable to conventional urban drainage systems. However, the effects of the combined use of different LID facilities on urban flooding have not been fully investigated under different rainfall characteristics. In this study, a residential, neighborhood-scale catchment in Shenzhen City, southern China was selected as a case study, where the effects of four LID techniques (bio-retention, bio-swale, rain garden and pervious pavement) with different connection patterns (cascaded, semi-cascaded and paralleled) on runoff reduction efficiency were analyzed by the storm water management model (SWMM), promoted by the U.S. EPA. Three kinds of designed storm events with different return periods, durations and time-to-peak ratios were forced to simulate the flood for holistic assessment of the LID connection patterns. The effects were measured by the runoff coefficient of the whole storm–runoff process and the peak runoff volume. The results obtained indicate that the cascaded connect LID chain can more effectively reduce the runoff than that in the paralleled connect LID chain under different storms. The performances of the LID chains in modeling flood process in SWMM indicate that the runoff coefficient and the peak runoff volume increase with the increase in the rain return periods and the decrease in rain duration. Additionally, the move backward of the peak rain intensity to the end of the storm event slightly affects the peak runoff volume obviously while gives slight influence on the total runoff volume. This study provides an insight into the performance of LID chain designs under different rainfall characteristics, which is essential for effective urban flood management.

Toward sustainable stormwater management: Understanding public appreciation and recognition of urban Low Impact Development (LID) in the San Francisco Bay Area

In the United States, regulators, planners, and designers have promoted Low Impact Development (LID) as a landscape-based approach to better manage urban stormwater for ecological benefits. However, the projects have often failed to achieve positive public responses due to their unattractive and unkempt appearances. This study provides empirical insights into public perception of urban LID practices by studying user reactions to 16 sites located in the San Francisco Bay Area—eight with LID design and eight with conventional landscape design. Most of the 502 respondents, although expressing some misconceptions and limited stormwater knowledge, showed their appreciation and recognition of the LID landscapes. This finding implies that the implementation of new LID facilities can be continued and expanded without serious concern about strong public resistance, and suggests that the design of these existing LID sites can serve as models for the future projects in the San Francisco Bay Area, along with other urban areas. The study confirms the important role of picturesque beauty, naturalness, and neatness in satisfying public expectations, especially for aesthetic and ecological landscapes. Interestingly, interpretive signs appeared to be the preferable means for motivating stormwater education and the powerful means for producing positive public reactions to LID sites, suggesting the potential of urban LID projects as the venues for public education and outreach. The study not only emphasizes the alignment of aesthetics and ecology to enhance public satisfaction, but also promotes the aesthetic qualities and didactic opportunities as the essential components of LID implementation.

Modelling the effect of rainfall patterns on the runoff control performance of permeable pavements.

With the implementation of low impact development (LID) in urban areas, it is necessary to quantify the actual effectiveness of LID facilities. In this study, a coupled hydrology-hydrodynamic numerical model was utilized to investigate the runoff control effectiveness of permeable pavements in the city centre of Shijiazhuang, China. Two groups of designed rainfall events with the same duration but different rainfall amounts and peak rainfall intensity locations were presented, and the effectiveness of permeable pavement was demonstrated by the reduction in the total runoff volume, water depth, and inundated area. The results indicate that the rainfall amount is the main factor affecting the runoff control of permeable pavements, and their effectiveness decreases with increasing rainfall amounts and peak intensity coefficients. Moreover, permeable pavements are more effective in reducing the residential waterlogging area, and the proportion of the inundated area above a depth of 0.2 m is considerably diminished. This study reveals the response of the runoff control of permeable pavements to different rainfall patterns, which is essential for supporting the design and practical operation of permeable pavements.

The applicability of LID facilities as an adaptation strategy of urban CSOs management for climate change

Abstract The magnitude and frequency of extreme rainfall due to climate change is increasing. Increasing rainfall causes serious hydrological problems in cities. Rainfall does not infiltrate the soil, but mostly flows through the sewer pipes into the stream. Most old urban watersheds have combined sewer pipes. When rainfall exceeds the capacity of the combined sewer pipes, sewage mixed with stormwater overflows the sewer pipes and flows directly into the stream. This is called Combined Sewer Overflows (CSOs). CSOs enter the stream with non-point source pollutants accumulated on the surface and pollute the stream. CSOs are one of the major water quality problems in older urban watersheds. This can be solved by replacing the combined sewer pipes with separated sewer pipes, but in reality it requires astronomical costs. As an alternative, the Low Impact Development (LID) technique has recently been introduced. In this study, we analyzed the effects of climate change on CSOs in urban watersheds and applied LID techniques to offset the effects. The LID facility was applied with the most commonly used Bio-Retention cells.