Vattenbehovet stiger i världen till följd av ökande befolkning. Med ökad urbaniseringskapas mer hårdgjorda ytor där föreningar ackumuleras. Dagvattnet transporterar dessa föroreningar som således kan nå grundvattnet. Ett miljömål har antagits i Sverigeför att skydda grundvattentäkter och därmed säkra framtida dricksvattenförsörjning. Rullstensåsar innehåller stora grundvattenmagasin och har hög infiltrationsförmåga för vatten från markytan. Uppsala kommun tar 95 % av sitt dricksvatten från rullstensåsenUppsalaåsen. Ulleråker ligger strax söder om Uppsala stadskärna och i området planerasen ny hållbar stadsdel. Stadsdelen ligger delvis rakt på Uppsalaåsens kärna och det ärviktigt att inget förorenat dagvatten kan infiltrera åsen då det kan påverka dricksvattenförsörjningennegativt. Syftet med detta projekt är att bidra till en djupare förståelse för hur grundvattnet kan påverkas av dagvattenhanteringen vid den planerade nybyggnationen av Ulleråker. Målet med projektet är att utvärdera vad hållbar dagvattenhantering innebär och hur tekniken är planerad att implementeras i Ulleråker. Projektet innefattar även utvärderingav alternativa tekniker som applicerats i andra stadsbyggnadsprojekt med hållbarhetsprofil som skulle kunna tillämpas i Ulleråker. Projektet är till största delen en litteraturstudie där planprogram för Ulleråker studeratsför att identifiera och utvärdera risker som kan uppstå till följd av dagvattenhanteringen,men även för att utvärdera de åtgärder som planeras. En modellering utfördesäven för att studera föroreningsspridning från en bilväg i området. Slutligen studeradesandra stadsbyggnadsprojekt för att se om deras lösningar skulle kunna implementeras i Ulleråker. De främsta riskerna för grundvattenkvaliteten relaterade till dagvattenhantering i Ulleråker har identifierats till släckvatten vid brand, dagvatten- och avloppsledningarsamt utsläpp under byggnationen. Planerade åtgärder är att utifrån sårbarhetsområdensätta restriktioner för markanvändningen och hur byggnationen ska gå till, särskilt vidåskärnan. Dagvattenhantering ska utgå från ett robust dagvattensystem baserat på ettsystemtänk genom att inget dagvatten ska infiltrera marken i sårbara områden. Detta ska säkerställas genom ett tätt vattenledningssystem som avleder dagvattnet till dagvattendammardär det fördröjs och renas. Hantering av släckvatten vid bränder ska ske genom att täta markytor kring byggnader hindrar släckvatten från markinfiltration. Endast vatten får användas som släckvätska. Modelleringen över föroreningsspridning frånen bilväg i Ulleråker visar att föroreningar avsätts på en yta upp till 6 meter från vägbanansmitt. Ett annat stadsbyggnadsprojekt som studerades var Augustenborg i Malmödär dagvattensystemet bygger på öppna lösningar med bland annat kanaler, dammar ochgröna tak. Slutsatserna är att hållbar dagvattenhantering generellt går ut på att fördröja ochrena dagvattnet lokalt. De lösningar som tagits fram för Ulleråkers dagvattenhanteringbygger på täta ledningar och dammar som fördröjer vattnet innan det når ytvattenrecipienten Fyrisån eller kopplas på Uppsala kommuns dagvattenledningar. I Ulleråker blir det viktigt att kontrollprogram finns och efterföljs för att minska risken för förorening av grundvattnet. Föroreningar från Ulleråkersvägen sprids upp till 6 meter ut från vägensmitt och det är således viktigt att täta denna yta så att föroreningarna inte kan infiltreramed dagvattnet ner till Uppsalaåsen. Lösningar från Augustenborg som skulle kunna implementeras i Ulleråker är gröna tak med tjocka jordlager då de renar vatten mer effektivtän tak med tunnare jordlager. / Water demand rises in the world as a result of increasing population. Increased urbanizationcreates more impervious surfaces where pollutants accumulate. The stormwater transports these pollutants, which can thus reach the groundwater. An environmental goal has been adopted in Sweden to protect the groundwater and thus secure future drinking water supply. Eskers contain large groundwater storages and have high infiltration capacity for water fromthe ground surface. Uppsala municipality takes 95 % of its drinking water from the Uppsalaesker. Ulleråker is located just south of Uppsala city centre and in the area a new sustainabledistrict is planned. The district is partly located on the Uppsala esker’s core and it is importantthat no contaminated water is able to infiltrate the esker as it may affect the drinking watersupply negatively. The purpose of this project is to contribute to a deeper understanding of how the groundwatercan be affected by the stormwater management in the planned new construction of Ulleråker.The aim of the project is to evaluate what sustainable stormwater management means andhow the technology is planned to be implemented in Ulleråker. The project also includesevaluation of alternative techniques applied in other urban construction projects with sustainability profile that could be implemented in Ulleråker. The project is mainly a literature study where Ulleråker's plan program has been studied to identify and evaluate risks that may occur as a result of stormwater management, but also to evaluate the planned measures. A modelling was also conducted to study pollutant dispersio nfrom a roadway in the area. Finally, other urban construction projects were studied to see if their solutions could be implemented in Ulleråker. The main risks of groundwater quality related to stormwater management in Ulleråker have been identified as extinguishing water in the event of fire, stormwater and sewage pipelinesand leakage during construction. The planned measures are to impose restrictions on land usebased on vulnerability areas and how the construction is executed, especially at the core of the esker. Stormwater management should be based on a robust water system based on a system thinking so that no water will infiltrate the soil in vulnerable areas. This is to be ensured by a dense water pipeline system that leads the stormwater into surface water dams where it isdelayed and cleaned. Handling of extinguishing water should be done by sealing land surfaces around buildings preventing extinguishing water from soil infiltration. Only water may beused as extinguishing fluid. The modelling of pollution dispersion from a roadway inUlleråker shows that contaminants are deposited on a surface up to 6 meters away from the centre of the roadway. The studied urban building project Augustenborg in Malmö has its stormwater system based on open solutions, including channels, ponds and green roofs. The conclusion is that sustainable stormwater management in general is based on delayingand cleaning stormwater locally. The solutions developed for Ulleråker’s stormwatermanagement are based on dense conduits and ponds that delay the water before reaching thesurface water receptor Fyrisån or are connected to Uppsala municipality's water pipelines. In Ulleråker it becomes important that control programs are in place and followed to reduce therisk of groundwater contamination. Pollution from Ulleråkersvägen is spread up to 6 meters out of the middle of the road and it is therefore important to seal this area so that thecontaminants cannot infiltrate with the stormwater to Uppsalaåsen. Solutions from Augustenborg that could be implemented in Ulleråker are green roofs with thick soil layers asthey clean water more efficiently than roofs with thinner soil layers.

Stormwater management is a problematic area and has during the last 20 years been given an increased attention due to more pollution in the cities. The increased pollution and contaminants in stormwater implicates risks for animals, humans, the ecosystem and receiving recipients. Due to the increased attention, authorities, government and other stakeholders have developed measurements to deal with the problem. Stormwater accommodations and other type of stormwater detainment has been developed with increased modern technology and functionality to fit specific areas where different type of pollutants can vary. Stormwater treatment are necessary because it creates social, environmental and technical advantages combined with protection of ecosystem, increased multifunctionality when combining for example stormwater ponds in nature, parks or urban and rural environment. This report describes seven diverse types of stormwater accommodations systems; rain garden, stormwater ponds, wells, screen basins, infiltration trenches, pipe-/concrete magazine and swales in accordance from Structor Mark Stockholm. From these seven accommodations, three were chosen to be included in Multi Criteria Decision Analysis (MCDA). The purpose of the MCDA was to evaluate four different categories linked to stormwater, which are environment, social, technology and economical categories. These categories are broad concepts; therefore, parameters were developed to narrow down the areas within the concept, from which the area of investigation was founded within. The parameters created for each category are degree of purification for the environmental category, performance and maintenance for the technological category, aesthetical and social benefits for the social category and costs and risk for the economical category. The criteria developed from these parameters are specific topics that was scored from the scale between 0-5, where 0 = insignificant, 1= Low, 2= Moderate, 3= Major, 4=High, 5= Very high. A reference option was also created, considered as “no commercial treatment of stormwater”, only to transport stormwater. This reference option was also referred to as a zero-alternative and is drainage by piping. The scoring was conducted by stakeholders and citizens of Stockholm. The scoring of the three chosen stormwater accommodations and the reference alternative after calculating the mean value and summarize it resulted in that stormwater pond received the highest overall score of 11.9 followed by rain gardens 11.4, infiltration trench 11.3 and drainage by piping 7.3. The stakeholders are influential people that works either with stormwater, layout and planning or maintenance personnel. Citizens of Stockholm provided inputs only in regards of the social aspects. A total of 20 stakeholders were contacted and 5 stakeholders participated in the scoring procedure. Citizens were interviewed on the street; a total of 60 people was asked to participate and 13 people decided to participate in the scoring procedure of the social aspects. Although, the attendance of stakeholders was low, they are still considered important to this project since they provided the scoring of the criteria for each respective category (environment, technology, social and economic). In regards of the low attendance by stakeholders, this resulted in a way that it became hard to distinguish the result between the different stormwater accommodation. Therefore, it was hard to determine which stormwater accommodation that was the best out ofthe ranking provided by the MCDA. A benefit by using MCDA as a tool in this case, gave an indication that the MCDA can work as a framework to decision makers, even though the result in this case became difficult to manage and distinguish between the different stormwater accommodations. Finally, the method, layout and analysis itself can provide means of measurements for stormwater investigations when the purpose is to choose between the best stormwater systems included in the MCDA. Inputs from stakeholders concluded that depending on what type of existing circumstances, there must be a site-specific evaluation to treat every area as a unique area, before deciding what type of stormwater accommodation to apply to that specific location. / Dagvattenhantering är ett problematiskt område som under de senaste 20 åren har fått allt mer uppmärksamhet då mer föroreningar uppdagats i städerna. Den ökande föroreningen av dagvatten tenderar att orsaka en större risk för djur, människor, ekosystem och recipienter dit dagvatten rinner. På grund av uppmärksamheten som dagvattenhanteringen har fått, har myndigheter, regering och andra intressenter utvecklat dagvatten teknologin ytterligare för att skapa en modern dagvattenstrategi för att handskas med problemet. Dagvattenhantering är nödvändigt eftersom den skapar sociala, miljömässiga och tekniska fördelar samt om dagvattensystemen kombineras med funktionalitet så kan detta ge ökat skydd för ekosystemen samt förbättrad hälsa hos befolkningen i städerna. Den här rapporten beskriver sju olika typer av dagvattensystem så som; rain gardens, dagvattendammar, brunnar, skärmbassänger, svackdiken, rör-/betong magasin samt krossdiken på begäran av Structor Mark Stockholm. Utav dessa 7 dagvattensystem, ingick 3 anläggningar i en så kallad multi-criteria decision analysis (MCDA). Syftet med en MCDA är att utvärdera fyra olika kategorier som kan förknippas med dagvattenhantering. Kategorierna är miljömässiga, sociala, tekniska och ekonomiska. Dessa kategorier utger dock ett brett budskap och för att begränsa analysen så skapades parametrar. Dessa parametrar skapas utifrån varje enskild kategori. För den miljömässiga kategorin skapades parametern grad av rening, för den tekniska kategorin skapades parametern prestanda och underhåll, för den sociala kategorin skapades parametern estetiska och sociala fördelar, och slutligen för den ekonomiska kategorin skapades parametern kostnader och risker. Utifrån dessa parametrar skapades sedan kriterier med specifika huvudämnen som kan bedömas enligt en poängskala från 0-5 där 0 = insignificant, 1=Low, 2= Moderate, 3= Major, 4= High, 5= Very high. Tre dagvattensystem inkluderas i MCDA vilket var; rain gardens, dagvattendammar, krossdiken vars syfte är att rena och fördröja dagvatten. Ett referensalternativ skapades också som ävenkallas ”zero-alternative”, vilket anses inte ha någon rening av dagvatten utan är endast ett transportsystem för dagvatten. Detta referensalternativ kallas drainage by piping. Poängsättningen gjordes av intressenter och invånare i Stockholm. Intressenterna är människor som arbetar med dagvattenhantering antingen på planeringsstadiet eller ute i fält som drift och underhålls personal. Invånare i Stockholm bedömde endast den sociala kategorin eftersom det kan sakna kunskap och insyn i det miljömässiga, tekniska och ekonomiska detaljerna. Totalt kontaktades 20 intressenter där 5 personer valde att medverka i MCDA. Invånare i Stockholm intervjuades på stan, totalt frågades ca 60 personer varav 13 personer valde att medverka i poängsättningen. Poängsättningen av de tre valda dagvattensystemen samt referensalternativet, efter beräkningav medelvärdet samt den totala summeringen resulterade i att dagvattendammar fick den hösta poängen 11,9 hamnade rain garden på andra plats med 11,4, krossdike på tredje plats med 11,3 samt referensalternativet på en fjärde plats med 7,3. De tre dagvattensystemen hade ett relativt liknande slutgiltigt resultat. Dock så skilde sig den individuella kategoriska bedömningen av miljömässiga, tekniska, sociala samt ekonomiska aspekten med större varierande resultat. Även om deltagandet av intressenter var relativt lågt, endast 25 % av det kontaktade intressenterna valde att ställa upp, så anses dessa intressenter vara viktiga för det här projektet då de, utifrån deras kunskap, bedömer det uppsatta kriterierna och det är denna bedömning som resultatet baseras på. Resultaten mellan det olika dagvattenanläggningarna som var inkluderade i MCDA var svåra att särskilja, troligtvis beroende på att ingen viktningsmetod användes. Däremot så är en fördel med MCDA som verktyg i det här fallet, att det gav en indikation på att MCDA kan fungera som ett stödjande verktyg för beslutsfattare även om resultatet i det här fallet var svårt att särskilja. Själva metoden, upplägget och analysen kan användas som medel för att avgöra vilken typ av dagvattenanläggning som passar bäst utifrån de kriterier som är uppsatta. Slutligen så gav intressenterna en påvisning att dagvattenanläggningar ska konstrueras så att hänsyn tas till omkringliggande omständigheter, där varje plats ska ansesvara unik. Det krävs en platsspecifik utredning där hänsyn till geologiska, geotekniska,hydrologiska samt infrastrukturella och miljömässiga aspekter bör utredas innan valet av dagvattensystem bestäms.

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This project is established on the following questions:  How can Stockholm adapt to increasing extreme rainfall events through combined stormwater drainage strategies?How can social sustainability be implemented in stormwater treatment?How can stormwater and social design educate the public about the importance of clean water bodies?  Global and national trends show that annual precipitation is increasing, and extreme weather events are becoming more common. Urban landscapes are more susceptible to cloudburst flooding due to impervious surfaces. Additionally, when the stormwater runoff reaches water bodies, it can pollute its recipients unless the stormwater is treated beforehand. Stockholm is an urbanised area with several surrounding water bodies of various sizes that are burdened by human activity, and the water quality in most water bodies is currently at an unsatisfactory ecological and chemical level.  The project site has been determined through mapping, where the accumulation of stormwater flows have been mainly considered. Another important factor is the socio-economically vulnerable aspect, to be able to tackle the social sustainability aspect. For this project, the lake Magelungen is the water body targeted, and the connected site is Hagsätra. This project is using a holistic approach to stormwater management, where the design of recreational spaces, such as parks and playgrounds, can be utilised to serve an ecological as well as a social purpose. A set of toolboxes have been set forth through research and case studies which have been contextualised in the site through sequences and strategies.

Long-term hydrologic and nonpoint source (NPS) pollutant response is quantified for four headwater basins of the Occoquan River in northern Virginia using 24 years of observed rainfall, basin discharge, water chemistry, and derived land use/land cover (LULC) data. Long-term summaries document that several hydrologic and NPS pollutant delivery characteristics in the urbanizing Cub Run basin are significantly different from adjacent non-urban basins. Higher annual NPS fluxes of total suspended solids (TSS), phosphorus (P), and nitrogen (N) in Cub Run are identified with periods of increased soil disturbance from urban land development and significantly increased storm volumes resulting from higher mean impervious cover. Long-term summaries of nutrient flux are consistent with literature documenting increased ratios of particulate to soluble nutrients with increased discharge. Storm fluxes of NPS particulate P, soluble P, particulate N, and soluble N make up 92, 67, 89, and 50 percent, respectively, of total NPS nutrient fluxes from all headwater basins, with between 88 and 98 percent of mean annual TSS fluxes delivered by storm flow. Higher sediment and nutrient fluxes observed in Cub Run basin during the summer and fall growing season after 1983 demonstrate the impact of replacing vegetated cover with urban impervious surface (IS). Annual regression models indicate that mean IS above 10 percent and precipitation are significantly associated with total basin discharge (r2=0.65). The positive association of annual storm soluble phosphorus flux with cumulative mean IS suggests the need for continued evaluation of urban NPS soluble phosphorus strategies. Urban soil disturbance is indicated by measuring the annual change in mean IS (delta IS). Regression models show that urban soil disturbance is a significant source of TSS flux in all seasons. Long-term total soluble phosphorus and nitrogen fluxes are significantly and positively associated with precipitation, delta IS, and agricultural land use (r2=0.50 and 0.58, respectively). The significant impact of urbanization on hydrologic and NPS pollutant flux, especially during the growing season, is a major finding of this study. / Ph. D.

Stream ecosystems are increasingly at risk for thermal impairment as urbanization intensifies, resulting in more heated runoff from impervious cover that is less likely to be cooled naturally. While several best management practices, including bioretention filters, have been able to reduce thermal pollution, success has been limited. The extent of thermal mitigation required to prevent ecological damage is unknown. A calibrated runoff temperature model of a case study watershed in Blacksburg, VA was developed to determine the cumulative treatment volume of bioretention filters required to reduce thermal impacts caused by runoff from development in the watershed to biologically acceptable levels. A future build out scenario of the study watershed was also analyzed. Results from this study established that runoff thermal pollution cannot be fully reduced to goal thresholds during all storms using bioretention filter retrofits. While retrofitting significantly decreased temperatures and heat exports relative to the controls, increasing treatment volumes did not really enhance mitigation. Alternate thermal mitigation methods which actively remove runoff volume should be considered where more thermal mitigation is required. / Master of Science / Stream temperature is a significant ecological, biological, and chemical property affecting the long-term health of streams. However, as development intensifies, stream ecosystems are increasingly at risk of being damaged by thermal pollution, which causes warmer and less stable temperatures that distress aquatic organisms. While several stormwater management methods that reduce runoff-related pollution, known as best management practices (BMPs), were found to also decrease thermal pollution, their success has been limited. Furthermore, the extent of thermal mitigation required to prevent ecological damage is unclear. This study aimed to determine how much treatment by a popular BMP, the bioretention filter, was necessary across a watershed in Blacksburg, VA to adequately reduce thermal pollution to protect stream health. Mitigation impacts were tested on both existing and predicted future development conditions through model simulations. Results from this study established that thermal pollution from runoff cannot be fully reduced to goal thresholds consistently using bioretention filter retrofits. While retrofitting significantly decreased thermal pollution, increasing treatment volume did not considerably enhance mitigation. Results suggested that bioretention filters are not an effective method, and alternate thermal mitigation practices which actively remove runoff volume should instead be considered where intensive reductions in thermal pollution are necessary.

Authorities of municipal separate storm sewer systems (MS4s) are required to address illicit discharges as part of the National Pollutant Discharge Elimination System (NPDES) stormwater program. Field reconnaissance is an effective measure to detect and identify illicit discharges, but requires substantial staff and financial resources to conduct. While risk analysis techniques and guidelines have been developed to facilitate MS4 prioritization of field operations, neither a standard set of indicators nor a standard operating procedure has been adopted. This study investigates the relationships among indicators of illicit discharge potential (IDP) and the locations of illicit discharges in two Virginia MS4s. Results of the study indicate that certain risk factors are statistically more effective at predicting IDP, suggesting that a core set of factors can be used to map illicit discharge risk. The results also show that risk mapping tools are significantly impacted by uncertainty in model inputs. Recommendations are provided for MS4s interested in pursuing IDP risk mapping as a tool to improve cost-effectiveness and guide illicit discharge program implementation. / Master of Science

The use of real-time control (RTC) as an adaptation technique for improving existing stormwater systems has been gaining attention in recent years for its ability to enhance water quality and quantity treatment. A case study RTC retrofit of seven existing detention basins was simulated for a small (162 ha), urbanized watershed in Blacksburg, VA. Two heuristic, reactive control algorithms were tested and compared for their ability to improve hydraulic conditions at each detention basin and the watershed outlet through manipulation of an actuated valve, under various permutations of RTC retrofitting (single facility, multiple facilities, etc.). Change in peak flow during 24-hour design storms was assessed. RTC only reduced peak flows at some of the facilities for storms with a return period of 2 years or less. For larger storms, RTC maintained or increased peak flow rates. During a 15-year simulation with historic precipitation data, total duration of erosive flows was reduced for most facility retrofit simulations; however, the duration of high intensity flows increased, or remained unchanged. This result was also reflected at the watershed outlet. / Master of Science / Stormwater management helps protect natural waterways from the harmful impacts of human development. A growing field of research is investigating the potential for “smart” technologies to improve the efficiency of existing stormwater facilities. This study investigates the application of a “smart” stormwater retrofit, known as real-time control (RTC), to existing stormwater management facilities located in a small case study watershed. The RTC system is composed of hypothetical internet-connected sensors and control valves which control flows at several points within the test watershed. Two control algorithms were tested, and compared to the current conditions (scenario with no RTC), for a large range of storm events. Results of this study found that RTC would lead to improved stream health for most rainfall events, but could potentially worsen conditions for the largest, most rare storm events. In addition, RTC was found to be much more effective at some points in the watershed than other points. Prediction of where RTC will be most effective should be the focus of future research.

Snow handling practices are managed by Swedish municipalities, and urban snow is usually removed to be placed at a central or local snow deposit. Snow deriving from urban areas can contain environmental pollutants in various extents. Through atmospheric deposition, traffic emissions and road maintenance strategies, urban snow accumulates pollutants such as metals, organic and inorganic compounds, which in turn spread to receiving waters and soil through the meltwater. During wintertime, snow is ploughed and removed from highways and roads to insure safe conditions for drivers, cyclists, and pedestrians. This study has analyzed Swedish municipalities snow handling strategies regarding current environmental law and degree of environmental protection on land-based snow deposit sites. Through a semi-qualitative web survey sent to all 290 Swedish municipalities, respondents were asked questions regarding the organization’s snow handling strategies and environmentally protective actions within their snow deposits. The results of this study showed that the use of snow deposits varies in different regions, and that most snow deposits are not equipped with any technical infrastructure to mitigate eventual environmental effects on the local environment. Environmental management in the form of systematic sampling of snow, soil, groundwater and receiving waters are found to be rare, which sequentially makes it difficult for municipalities to investigate the possible local environmental effects caused by depositing snow. In conclusion, environmental investigation and protection at snow deposit sites can be crucial to hinder further local pollution in some areas, but is as of yet not constantly executed by current practices.

Implementing optimal Low Impact Development (LID) practices has grown in popularity as a means of mitigating the adverse effects of urbanization and climate change. As such incorporating aspects of resilience for optimal LID design has become paramount. This study focuses on identifying the current LID optimization strategies and associated research gaps as well as assessing whether a quantitative approach to measure LID resilience exists. To do so, a systematic and bibliometric literature review on LIDs optimization and resilience is first conducted, based on which resilience, climate change, and uncertainty are recognised as hotspot keywords. The review also showed that no LID resilience quantification technique was available. Based on the latter outcome and to facilitate LID’s optimal design in future, this research proposes a new resilience quantification approach of LID by developing set of equations using Analytical Probabilistic Approach (APA) and continuous simulation approach using SWMM. The equations consider LID’s functionality and assess resilience using three indices: robustness, rapidity and serviceability. A new overall resilience index (the product of robustness and serviceability) and reliability index (the product of volumetric, occurrence, and temporal reliability) are proposed using different area ratios between contributing catchment and LID area to assure a resilient and safe LID system. LID costing tool of the Sustainable Technologies Evaluation Program (STEP) is subsequently utilized to estimate the capital cost of LID. Finally, a user-oriented design guideline is proposed for a cost-effective, resilient, and reliable LID system. Although this study adopts bioretention (BR) as a demonstration of the approach utility, the developed approach is applicable to any form of LID practices. / Thesis / Master of Applied Science (MASc) / There is a critical need to develop and implement optimal low-impact development (LID) practices in the field of stormwater management to mitigate the adverse effects of urbanization and climate change. This thesis is focused on developing quantitative resilient measurement approach of LID designs. A comprehensive literature review is first carried out, focusing on identifying various optimization methodologies, relevant gaps, and resilience assessment techniques. Subsequently, a novel resilience evaluation approach is developed, using bioretention (BR). By constructing a new reliability index, the entire BR system's reliability can also be assessed. Finally, a cost-effective, resilient and reliable design guideline for BR system is proposed. Although bioretention (BR) is used as an example in this study, the developed approach opens the gate to quantify the resilience of all types of LID practices.