Low Impact Development Technologies Research Articles

Life cycle assessment of low impact development technologies combined with conventional centralized water systems for the City of Atlanta, Georgia

Low-impact development (LID) technologies, such as bioretention areas, rooftop rainwater harvesting, and xeriscaping can control stormwater runoff, supply non-potable water, and landscape open space. This study examines a hybrid system (HS) that combines LID technologies with a centralized water system to lessen the burden on a conventional system (CS). CS is defined as the stormwater collection and water supply infrastructure, and the conventional landscaping choices in the City of Atlanta. The study scope is limited to five single-family residential zones (SFZs), classified R-1 through R-5, and four multi-family residential zones (MFZs), classified RG-2 through RG-5. Population density increases from 0.4 (R-1) to 62.2 (RG-5) persons per 1,000 m2. We performed a life cycle assessment (LCA) comparison of CS and HS using TRACI 2.1 to simulate impacts on the ecosystem, human health, and natural resources.We quantified the impact of freshwater consumption using the freshwater ecosystem impact (FEI) indicator. Test results indicate that HS has a higher LCA single score than CS in zones with a low population density; however, the difference becomes negligible as population density increases. Incorporating LID in SFZs and MFZs can reduce potable water use by an average of 50% and 25%, respectively; however, water savings are negligible in zones with high population density (i.e., RG-5) due to the diminished surface area per capita available for LID technologies. The results demonstrate that LID technologies effectively reduce outdoor water demand and therefore would be a good choice to decrease the water consumption impact in the City of Atlanta.

Rooftop Rainwater Harvesting as an Alternative Domestic Water Resource in Zambia

Within the last decade, substantial progress has been achieved in the management of centralized water reticulation in Zambia. Characterized by diversified fiscal resourcing, concurrent institutional restructuring and introduction of new players in water governance, the water sector is set to achieve improved reliability on sustainable grounds. However, the threat of underground water pollution resulting from increased urbanization besides the unreliable energy sector presents new challenges for the current urban water. In effect, urban areas are affected by chronic water rationing creating public stress and insecurity which impacts domestic development. While the course of development has meant investment in the extension and expansion of water infrastructure in Zambia, alternative urban water resources are being sought to address challenges of traditional water systems globally. This paper therefore attempts to make a case for the modernization of Rooftop Rainwater Harvesting (RRWH) as an augmenting water resource in the Zambian urban housing sector. Here—in, it is identified as a Low Impact Development technology within the Integrated Urban Water Management framework currently being forged by local water. Based on a desktop literature survey and online questionnaire survey, an argument to support the development of RRWH in Zambia was developed. While literature survey results revealed evidence of economic loss and a growing compromise to public health resulting from inconsistent water supply in the study area of Lusaka city, the online questionnaire survey depicted significant domestic stress due to erratic water supply. Results confirmed that at one time residents observed an average of eight hours of power blackouts which effectively induced water disruption forcing homeowners to engage in various water storage methods which in turn are costly on domestic time, health and finances. A retrospective discussion based on both survey results attempts to present benefits and opportunities of urban RRWH to water sector stakeholders providing recommendations towards the mainstreaming of the practice in Zambia.

Data Integration and its Application in the Sponge City Construction of CHINA

Under the climate change and the unfettered expansion of urbanization, problems associated with urban waterlogging, water resources, and the aquatic environment are becoming serious. In 2014, the Chinese government began to implement a plan to construct sponge cities in an effort to combat these problems. The construction of a sponge city is a complex task of systems engineering and requires the support of a high volume of data about the city's natural geography, social economy, water resources, and eco-environment. These data have multiple sources and are highly complex. Based on the problem existing of the currently urban data information monitoring, collecting and application, this paper puts forward a sponge urban data integration plan according to the integration of urban planning data, underground pipe network information, digital elevation information, hydrological station network information and based on the low impact development technology, urban waterlogging drainage, urban non-point source pollution prevention & control technologies integrated. The plan is designed for use in sponge city town planning, design, and construction, and as a theoretical framework for operations that rely on data and integrated technologies. This article has carried on the application of the data integration solutions in the Fenghuang county of Hunan Province, and the application effect is evaluated.

Coupling community preferences with hydrologic evaluation of low impact development implementation in an urban watershed

Stormwater runoff, and its associated pollutants, is a major problem in urban watersheds where the runoff is either channeled into surface water bodies or wastewater treatment plants. One emerging Best Management Practice (BMP) to control stormwater runoff is low impact development (LID). The EPA Stormwater Management Model (SWMM) was used to evaluate the hydrologic effectiveness at a watershed scale of five LID technologies (vegetated swales, bioretention cells, porous pavement, rain barrels and tree boxes) in an existing, typical urban watershed. As implementation focused on public transportation areas, hydrologic effectiveness of runoff reduction was assessed as a function of roadway length: and the impacts of LID implementation on traffic flow were modeled using VISSIM and TransCAD. Vegetated swales, the most cost effective option, captured 32% of the runoff with 100% roadway implementation. However, socio-economic factors limit potential mitigation implementation. Transportation modeling demonstrated negative impacts above 4 km of road length (16%), limiting runoff reduction to 2.5%, and non-roadway options such as rain barrels have limited hydrologic effectiveness. While porous pavement can be implemented without impacting transportation, cost is more prohibitive. Combinations of LID features, especially those that do not impact transportation, increase the amount of runoff mitigated. However, socio-economic considerations still limit runoff reduction at the watershed scale to ~15%, less than prior watershed-level evaluations. Our results demonstrate the need to implement LID approaches that account and plan for socio-economic considerations in addition to environmental factors.

The Management of Nonpoint Source and Storm Water Reduction with LID Techniques in Inchon City, South Korea

Impervious areas have been expanded by urbanization and the natural structure of water circulation has been destroyed. The limits of centralized management for controlling storm water runoff in urban areas have been suggested. Low impact development (LID) technologies have been promoted as a crucial alternative, establishing a connection with city development plans to build green infrastructures in environmentally friendly cities. Thus, the improvement of water circulation and the control of nonpoint source were simulated through XP-SWMM (storm water and wastewater management model for experts) in this study. The application of multiple LID combination practices with permeable pavements, bioretention cells, and gutter filters were observed as reducing the highest runoff volume by up to 70%. The results from four different LID installation scenarios indicated that permeable paving is the most effective method for reducing storm water runoff. The rate of storm water runoff volume reduced as the rainfall duration extended. Based on the simulation results, each LID facility was designed and constructed in the target area. The LID practices in an urban area enable future studies of the analysis of the criteria, suitable capacity, and cost-efficiency, and proper management methods of various LID techniques.

From Rain Tanks to Catchments: Use of Low-Impact Development To Address Hydrologic Symptoms of the Urban Stream Syndrome.

Catchment urbanization perturbs the water and sediment budgets of streams, degrades stream health and function, and causes a constellation of flow, water quality, and ecological symptoms collectively known as the urban stream syndrome. Low-impact development (LID) technologies address the hydrologic symptoms of the urban stream syndrome by mimicking natural flow paths and restoring a natural water balance. Over annual time scales, the volumes of stormwater that should be infiltrated and harvested can be estimated from a catchment-scale water-balance given local climate conditions and preurban land cover. For all but the wettest regions of the world, a much larger volume of stormwater runoff should be harvested than infiltrated to maintain stream hydrology in a preurban state. Efforts to prevent or reverse hydrologic symptoms associated with the urban stream syndrome will therefore require: (1) selecting the right mix of LID technologies that provide regionally tailored ratios of stormwater harvesting and infiltration; (2) integrating these LID technologies into next-generation drainage systems; (3) maximizing potential cobenefits including water supply augmentation, flood protection, improved water quality, and urban amenities; and (4) long-term hydrologic monitoring to evaluate the efficacy of LID interventions.

비점오염 저감시설에 적용되는 여재의 흡착 및 탈착 능력 평가

Urbanization causes many environmental, hydrological and ecological problems such as distortion of the natural water circulation system, increase in nonpoint source pollutants in stormwater runoff, degradation of surface water quality, and damage to the ecosystem. Due to the increase in impervious surface by urbanization, developed countries apply low impact development (LID) techniques as important alternatives to reduce the impacts of urbanization. In Korea, LID techniques were employed since 2012 in order to manage nonpoint source pollutants. LID technology is a technique for removing pollutants using a variety of physical, chemical and biological mechanisms in plants, microorganisms and filter media with the reduced effluence of stormwater runoff by mimicking natural water circulation system. These LID facilities are used in a variety of filter media, but an assessment has not been carried out for the comprehensive comparison evaluation of adsorption and desorption characteristics for the pollutant removal capacity. Therefore, this study was conducted to analyze the adsorption and desorption characteristics of various filter media used in the LID facilities such as sand, gravel, bioceramic, wood chips and bottom ash etc. in reducing heavy metals(Pb, Cu). In this study, the adsorption affinity for Pb in all filter media was higher than Cu. Pseudo second order equation and Langmuir-3 isotherm are more applicable in the adsorption kinetic model and adsorption isotherm model, respectively. As a result of the desorption experiment, the filter media does not exceed KSLT which is the hazardous substance leaching limit, showing the capability of the filter media in LID. The bioceramic and woodchip as filter medias were evaluated and exhibited excellent adsorption capacity for Pb.

Effects of Aggregate Masking on Soil Infiltration under an Aggregate Bed

This research seeks to address questions about the reduction in soil infiltration rates due to masking or embedding when a layer of open-graded aggregate is placed on top of soil. This is pertinent to the design and modeling of many low impact development (LID) technologies that incorporate infiltration such as porous pavements, infiltration trenches, and dry wells. A large permeameter was used to first measure the infiltration rate of five different soils and a No. 67 aggregate separately, and then measure the effective infiltration rate of the soils with an aggregate layer on top and with aggregate embedded in the top of the soil. The actual effective infiltration was then compared to the theoretical effective infiltration, assuming no masking or embedding effect. It was found that the measured infiltration rate was consistently lower than predicted, indicating a reduction in infiltration due to the presence of the aggregate layer. The average reductions were 29 and 43% for masking and embedding, respectively, which are consistent with computer modeling results from a previous study, but are significantly less than the reduction factors used in other porous pavement modeling applications. As such, existing modeling approaches for LID infiltration technologies may underpredict actual performance.

A Right-of-Way Stormwater Low Impact Development Practice

Road right-of-way can provide a good retrofit opportunity to implement stormwater low impact development (LID) technologies. In Canada and the northern United …

An evaluation of the Stormwater Footprint Calculator and the Hydrological Footprint Residence for communicating about sustainability in stormwater management

Low-Impact Development (LID) can enhance sustainability in stormwater management by attenuating excess runoff. Relevant technologies are typically implemented at individual lots and require the engagement of homeowners and developers. A new educational tool, the Stormwater Footprint Calculator (SFC), was developed to improve knowledge and change attitudes and behavior regarding stormwater sustainability. Similar to online carbon-footprint calculators, the SFC synthesizes a participant’s answers about lot and neighborhood-level land use and calculates hypothetical effects on instream flows, using hydrologic simulation. Participants receive feedback about their storm-water footprint using a new metric, the Hydrologic Footprint Residence (HFR), which measures the effect of urbanization on stream flow based on the duration and extent of flooding. An experiment was fielded to test the SFC as a tool for communicating about sustainable stormwater management and to compare the HFR against an orthodox stormwater metric, peak flow. A convenience sample of undergraduate students (N= 510) participated in the experiment. The results indicate that completing the SFC improves knowledge about the causes of stormwater runoff and LID technologies (although not about the effects of stormwater, which was already high among the students), and it influences intention to support sustainable stormwater management. The results also indicate that HFR provides a viable alternative to conventional engineering metrics for communicating a stormwater footprint and shows the value of online calculators for communicating complex civil engineering concepts.

도시 물순환 개선을 위한 도시기본계획과 저영향 개발(LID) 연계성 분석

최근 심화되고 있는 기후변화에 적응하고 도시의 물순환을 개선하기 위한 주요 전략으로 저영향 개발(Low Impact Development; LID)이 강조되고 있다. 저영향 개발의 효과적인 실현을 위해서는 도시계획과의 연계가 필수적이다. 그러나 국내에서는 아직 도시계획과 저영향 개발의 연계현황 분석과 연계방안에 대한 연구가 미흡한 상태이다. 이에 본 연구는 1) 현재 국내 도시계획 및 개발 관련 제도에서 저영향 개발에 대한 고려사항이 있는지 검토하고, 2) 도시계획의 기본방향과 전략을 제시하는 도시기본계획을 대상으로 계획분석 기법을 활용하여 저영향 개발과와의 연계성을 분석하여 그 방안을 제시하였다. 분석결과, 도시개발 관련 일부 사업지침에 저영향 개발이 반영되어 있으나, 선언적 수준의 내용만 포함되어 있어 도시계획 전반에 실질적 영향을 미치지는 못하고 있었다. 또한 7개 대도시의 도시기본계획을 대상으로 저영향 개발 계획요소와의 연계성을 검토한 결과, 획득가능점수의 약 19.52% (11.71점/60점)를 획득하여 현재까지는 도시기본계획에의 저영향 개발 반영 수준이 매우 낮으며, 도시 간 편차도 큰 것으로 나타났다. 도시계획 내 저영향 개발 주류화를 위해 저영향 개발을 주요 개발계획 원칙으로 명시하고, 부문별 계획에 비구조적, 구조적 저영향 개발 요소기술이 반영되도록 도시기본계획 수립지침이 개정될 필요가 있다. Recently, Low Impact Development (LID) has been emphasized as a critical strategy for improving urban water cycle and adapting to climate change. LID is needed to be incorporated in urban planning and development process for effective implementation in the real world. However, little research has examined the relationship between urban planning and LID in Korea. This study addresses this critical gap by 1) examining whether current urban planning institutional system considers LID or not and 2) assessing the extent to which local comprehensive plans integrate LID in seven large cities. Study results show that a few planning guidelines declaratively mention the need of LID but they don't include specific LID strategies. In addition, we found that 7 local comprehensive plans in the sample received a mean score of 11.71, which represents 19.52% of the total possible points and there are wide variations among cities. These findings indicate that there is still considerable room for improvement of local governments on LID. We propose the revision of planning guideline by incorporating LID principles and non-structural and structural LID technologies.

LID 기술의 효율성 검증을 위한 강우-유출 모의장치 개발 및 검증실험에 관한 연구

Climate change and urbanization have affected a increase of peak discharge and water pollution etc. In a view of these aspects, the LID(Low Impact Development) technology has been highlighted as one of adjustable control measures to mimic predevelopment hydrologic condition. Many LID technologies have developed, but there is a lack of studies with verification of LID technology efficiency. Therefore this study developed a rainfall-runoff simulator could be possible to verify LID technology efficiency. Using this simulator, this study has experimented the rainfall verification through the rainfall distribution experiment and the experiment to show the relation between inflow and effective rainfall in order to sprinkle the equal rainfall in each unit bed. As a result, the study defined the relation between allowable discharge range and RPM by nozzle types and verified the hydrologic cycle such as the relation between infiltration rate, surface runoff and subsurface runoff at pervious area and impervious area through the rainfall-runoff experiment.

저영향개발기법 적용을 통한 비점오염원 저감 및 비용효율 분석에 관한 실증적 연구 - 울산광역시를 대상으로 -

The purpose of this study is to identify the efficiency of LID technologies for controlling non-point source pollution from urban areas. The recent technical responses to managing water resource and urban areas according to the influence of climate change is an important national policy, along with green growth. Through various reference studies reasonable ways to consider a wholistic plan on urban-eco-friendly river management, the Low Impact Development (LID) as the adequate river management method is being undertaken in foreign countries to technically apply to urban plans. However, the LID is at the initial stage in Korea, with no specific studies implemented. Thus, this study explored whether LID technologies can be efficient measures to control non-point source pollution on the cost side. Ulsan's Namgu and Bukgu have been chosen as case studies that illustrate the efficiency of the LID technologies. On investigation, if LID technologies are designed properly, the efficiency of them is expected to higher than that of sewage treatment plant.

Climate Change Resilience and Public Education in Response to Hydrologic Extremes in Singapore

Aims: In February and March 2014, more than 300,000 households were affected by water rationing in Kuala Lumpur, Malaysia and the surrounding State of Selangor. Further south, reservoir levels in Singapore were dropping, prompting the government to raise the water conservation rhetoric, but falling short of implementing water rationing schemes. The region experienced a dry spell that was unprecedented in the last 30 years. Preparedness for storms has been the talk of the town since the 2001, 2006 and 2007 extreme high precipitation events in the southern parts of the peninsula and in Singapore resulted in costly flood damage. While resilience has been a concept used frequently in climate change adaptation, it is derived from ecology, where it refers to the capacity of the system to respond to a disturbance and resist the impact or recover from the damage of the disturbance. This paper examines the case of Singapore as an urban area in responding to a similar extreme hydrologic phenomenon by examining the climate Original Research Article British Journal of Environment & Climate Change, 4(3): 328-354, 2014 329 change resilience of the small city-state, with a view to recommending some considerations in designing climate change adaptation strategies. Place of Study: Singapore and peninsular Malaysia. Methodology: The paper reviews the rainfall extremes statistics covering the last 30 years for Singapore and then takes a hydrologic event-based case study approach to more closely examine the impact of record storms and the drought of March 2014 to discuss aspects of resilience that can serve as lessons for tropical cities in future adaptation to a climate-changing world. Results: Extreme rainfall events have become more frequent in Singapore over the past 30 years, while February, 2014 was the driest February since 1869. February, 2014 also had the lowest recorded daily relative humidity at 74.5%. Tropical cyclones are not expected to hit Singapore because of its location near the equator, yet Typhoon Vamei made history by delivering 210 mm of rain on 27 December, 2001. Between 19 and 20 December, 2007 Singapore received 366 mm of rain and within the same week another storm deposited 140 mm of rain in a 24 hour period. While there were some environmental and health impacts related to the February 2014 drought, including low dissolved oxygen levels in water and a localized fish kill, as well as reports of greater human respiratory problems, Singapore was able to weather the drought by requesting voluntary conservation measures, prudent reservoir management, and increasing the output of NEWater and desalinized water. Recent extreme rainfall events have produced localized flooding, but Singapore has progressively pursued a program of improved drainage, stream naturalization, and implementation of Low Impact Development (LID) technology to reduce flood-prone areas from 3,200 ha in the 1970’s to 36 ha today. Conclusion: We do not suggest that all countries need to have NEWater or desalinated water to solve drought problems. We do suggest that in managing rainfall related hazards, droughts and extremes have been treated rather independently. Based on the case study of extremes presented for Singapore we propose the importance of establishing a three-step preparedness program for extremes that includes Preparation (vulnerability and risk identification, adaptive capacity building, and monitoring), Response (information dissemination and relief action), and Recovery.

LID 기술 적용을 통한 공동주택단지 물순환 개선 연구 - 침투시설 적용을 중심으로 -

Change in the Global Climate causes flood, drought, heavy snow, and rainfall patterns in the Korean Peninsula. A variety of alternatives related to climate change are considered. The foreign researchers are interested in Low Impact Development(LID); the utilization of water resources and eco friendly development, over 10 years ago. The research and development of related technology has been advanced to apply LID techniques in order to develop several projects in the country. However, sharing of technology or system that can be used easily in the private sector is insufficient. The performance of the elements of LID Technology has not been fully agreed. LID elements of this technology are easy to apply to Apartment complex. The elements are classified technology. The infiltration of elements performs the functions of apartment complex landscaping space technology applied to the target. The water cycle simulation(SWMM 5.0) and technology the implementation of the effectiveness is also verified. For this purpose, three different places in apartment complex to target by SWMM5.0 U.S. EPA conducted utilizing simulated rainfall and applying LID techniques before and after the simulated water cycle (infiltration, surface evaporation, and surface runoff) were conducted. The importance of green space in the LID techniques of quantitative and qualitative storm water control as well as the role of Apartment Housing is to promote Amenity. Remember that the physical limitations of apartment complex and smooth water circulation system for the application of LID integrated management techniques should be applied. To this end, landscapes, architecture, civil engineering, environmental experts for technical consilience between the Low Impact Development efforts are required.

LID 시설로서 도로에 적용 가능한 수목여과시설 개발

본 연구는 Low Impact Development (LID) 시설로서 도로에 적용 가능한 수목여과시설을 개발 하고자 수행되었다. 수목여과시설의 적용가능성 및 효과 검증을 위해 Test-bed 규모의 시설을 조성하여 총 17개월(2011년 6월 ~ 2012년 11월)동안 모니터링을 수행하였다. 모니터링 결과, 누적강우량 2 mm 이하의 강우시 발생되는 강우유출량은 시설내 전량 저류 되며 20 mm 이상일 경우 유입유량의 최소 20%가 시설내 저류 되는 것으로 분석되었다. 강우량에 따른 오염물질별 저감효과를 분석한 결과, Total Pb는 70% 이상의 저감효율을 보여 오염물질 중에서 저감효과가 가장 뛰어난 것으로 나타났으며 중금속, 입자상 물질, 영양염류 및 유기물 순으로 저감효과가 높은 것으로 조사되었다. 오염물질별 평균 저감효율은 60~73%의 범위로 나타났으며 소규모 강우(10 mm 미만의 강우)시 10 mm 이상의 강우 일 때 보다 오염물질이 함유된 강우 유출수가 시설 내에서 충분히 저류되기에 오염물질 저감에 효과적인 것으로 분석되었다. 본 연구결과를 활용하여 강우량, 오염물질 저감효율과 같은 LID 시설의 설계인자를 도출할 수 있었으며 물순환 효과 및 오염물질의 효율평가를 통하여 향후 본 시설과 유사한 시설의 설계시 활용 가능성이 높은 것으로 판단된다. The aim of this study was to develop a tree box filter system, an example of Low Impact Development technology, for treating stormwater runoff from road. Monitoring of storm events was performed between June 2011 and November 2012 to evaluate the system performance during wet day. Based on the results, all runoff volume generated by rainfall less than 2 mm was stored in the system. The minimum volume reduction of 20% was observed in the system for rainfall greater than 20 mm. The greatest removal efficiency was exhibited by the system for total heavy metals ranging from 70 to 73% while satisfactory removal efficiency was exhibited by the system for particulate matters, organic matters and nutrients ranging from 60 to 68%. The system showed greater pollutant removal efficiency of 67 to 83% for rainfall less than 10 mm compared to rainfall greater than 10 mm which has 39 to 75% pollutant removal efficiency. The system exhibited less pollutant reduction for rainfall greater than 10 mm due to the decreased retention capacity of the system for increased rainfall. Overall, the system has proved to be an option for stormwater management that can be recommended for on-site application. Similar system may be designed based on several factors such as rainfall depth, facility size and pollutant removal efficiency.

Comparison of Maintenance Cost, Labor Demands, and System Performance for LID and Conventional Stormwater Management

The perception of the maintenance demands of Low Impact Development (LID) systems represents a significant barrier to the acceptance of LID technologies. Despite the increasing use of LID over the past two decades, stormwater managers still have minimal documentation in regards to the frequency, intensity, and costs associated with LID operations and maintenance. Due to increasing requirements for more effective treatment of runoff and the proliferation of total maximum daily load (TMDL) requirements, there is greater need for more documented maintenance information for planning and implementation of stormwater control measures (SCMs). This study examined seven different types of SCMs for the first 2-4 years of operations and studied maintenance demands in the context of personnel hours, costs, and system pollutant removal. The systems were located at a field facility designed to distribute stormwater in parallel, in order to normalize watershed characteristics including pollutant loading, sizing, and rainfall. System maintenance demand was tracked for each system and included materials, labor, activities, maintenance type, and complexity. Annualized maintenance costs ranged from $2,280/ha/yr for a vegetated swale to $7830/ha/yr for a wet pond. In terms of mass pollutant load reductions, marginal maintenance costs ranged from $4-$8 per kg/yr TSS removed

Multi-Objective Optimization of Low Impact Development Designs in an Urbanizing Watershed

Multi-objective optimization linked with an urban stormwater model is used in this study to identify cost-effective low impact development (LID) implementation designs for small urbanizing watersheds. The epsilon-Non-Dominated Sorting Genetic Algorithm II (e-NSGAII) has been coupled with the US Environmental Protection Agency’s Stormwater Management Model (SWMM) to balance the costs and the hydrologic benefits of candidate LID solutions. Our objective in this study is to identify the near-optimal tradeoff between the total LID costs and the total watershed runoff volume constrained by pre-development peak flow rates. This study contributes a detailed analysis of the costs and benefits associated with the use of green roofs, porous pavement, and bioretention basins within a small urbanizing watershed inState College,Pennsylvania. Beyond multi-objective analysis, this paper also contributes improved SWMM representations of LID alternatives and demonstrates their usefulness for screening alternative site layouts for LID technologies.

Bioretention cell efficacy in cold climates: Part 1 — hydrologic performance

Bioretention cells are an emerging low impact development technology that address urban stormwater runoff concerns. Field and column experiments were conducted to assess the efficacy of bioretention cells in cold conditions. Field experiments in a prairie environment demonstrated a significant decrease (91.5%) in effluent volumes compared to influent volumes. The majority (∼60%) of the runoff percolated to the surrounding soils or evapotranspirated. Cold condition performance significantly impacted high volume events and was characterized by significantly higher effluent volumes, significantly lower runoff storage, higher effluent peak flow rates, and longer peak delays. A partially frozen surface layer caused the changes in performance. Long-term simulation experiments on the columns indicated a significant decrease in saturated hydraulic conductivity over the first 4 equivalent years of operation, before levelling to a constant value.

Applying multi-criteria decision analysis to select WSUD and LID technologies

Water Sensitive Urban Design (WSUD) and Low Impact Development (LID) principles were investigated in Dhaka's drainage network using ‘Regime in Balance’ strategy for Average Recurrence Interval (ARI), Y = 100 years. Three feasible alternatives, such as, leaky-well, soak-away and infiltration trench were identified and designed to improve Dhaka's present unsatisfactory stormwater drainage system into one which is sustainable. For selecting the best one, we applied a multi-criteria decision analysis approach and chose the Analytic Hierarchy Process (AHP) model. Eleven criteria under three categories (technical, economic and social) were considered to quantify relative priorities of alternatives. Pair-wise comparisons of alternatives were performed against each criterion and ranked using a scale from 0 to 9. During the process of applying AHP model, consistency of ranking was thoroughly checked and a reasonable level of inconsistency was accepted due to the nature of human judgement. After the analysis, it was found that leaky-well (percentage priority 43%) followed by soak-away (38%) was the most appropriate technology for improving urban stormwater management system in Dhaka, Bangladesh. The proposed model can also be used in better selecting WSUD and LID technologies in other geographic locations.