Sustainable Drainage Systems Research Articles

How to evaluate nature-based solutions performance for microclimate, water and soil management issues – Available tools and methods from Nature4Cities European project results

In the context of climate change, Nature-Based Solutions (NBSs), a recently developed concept, are increasingly considered as part of the adaptation strategies of the cities. Studies using expert models and methods (EMM) receive a great deal of scientific attention. Considering EMM increasing use, this study aims to perform an analysis of the reported evaluation results, reflecting the capability of the EMM to accurately tackle urban challenges identified within the EU Nature4Cities project. Then, we propose a set of indicators and recommendations about sixteen EMM to be used by funders, researchers and practitioners when evaluating the performance of NBSs. The coupling of the different components (climate, water and soil) is not a simple matter. The analysis relies on the definition of the range of the reported metrics and on the investigation of the relationship between the various indices, applied for the EMM evaluation. Secondly, the study assesses the existing EMM, indicating the potential of NBSs: (i) to reduce urban heat island, (ii) to limit surface warming, (iii) to increase the thermal comfort of people, (iv) to limit the overheating and runoff of surfaces due to impervious areas, (v) to increase water retention during stormy episodes, (vi) to improve storm water quality at the outlet of the sustainable urban drainage systems, (vii) to promote the filtration and epuration of storm water runoff in soil and (viii) to be a support for vegetation. The analysis reveals that EMM can be considered as helpful tools for urban microclimate, urban soil and water management analysis, provided their limitations and characteristics are taken into account by the user when choosing tools and interpreting results (e.g. application scale). With regard to the performance of NBSs, the most commonly used indicators clearly depend on the scale of the project.

Development of a New Testing Approach for Decentralised Technical Sustainable Drainage Systems

A part of the sustainable drainage systems (SuDS) are used to treat stormwater and must be tested for their hydraulic performance and the removal efficiency to assess serviceability and retention of the pollutants efficacy for in situ use. Current test procedures provide a good basis for laboratory testing SuDS on the test stand. However, the evaluation is not sufficiently representative to compare different SuDS with each other or for in situ use. The individual steps and specifications of an applied test procedure in Germany were considered and evaluation and optimizations for the test substance and sampling methodology of SuDS on the test stand were proposed. A comparison of the particle size distribution of the test substance Millisil W4 currently in use and total suspended solids of real road runoff was made, which showed that the presented test substance of real road-deposited sediments (RDS) provides a better reference for the test conditions and they could be the basis for more representative test methods. A particle size distribution was proposed for this new test substance. Furthermore, two methods of sampling were compared, which showed that a full flow sampling is preferable to a discrete sample. At the same time, it was shown that a separation limit of 20 µm is sufficient for the determination of TSS63.

Sustainable Urban Drainage Systems in Spain: A Diagnosis

Sustainable urban drainage systems (SUDS) were almost unknown in Spain two decades ago; today, urban drainage in the country is transitioning towards a more sustainable and regenerative management in a global context where green policies are gaining prominence. This research establishes a diagnosis of SUDS in Spain and examines the extent to which the country is moving towards the new paradigm in three dimensions: (a) the governance and social perception of the community, (b) the regulative background, and (c) the implementation and the technical performance of SUDS. The diagnosis identifies barriers that hinder the change. Then, we define the challenges that Spain has to face to overcome obstacles that delay the transition. Barriers to the governance sphere are related to the lack of involvement, knowledge, and organisational responsibilities. Within the regulative framework, the absence of national standards hinders the general implementation at the national scale, although few regional and local authorities are taking steps in the right direction with their own regulations. From the technical perspective, SUDS performance within the Spanish context was determined, although some shortcomings are still to be investigated. Despite the slowdown caused by the hard recession periods and the more recent political instability, SUDS implementation in Spain is today a fact, and the country is close to reaching the stabilisation stage.

Sustainable stormwater management under the impact of climate change and urban densification

The demand for living space is rising in growing cities. To restrict urban expansion in the outskirts, a common strategy is to densify existing neighbourhoods. Densification implies the increase of water impervious area which increases the vulnerability to flooding during extreme precipitation events. Sustainable urban drainage systems are considered as a strategy to handle stormwater runoff locally and thus relieve the sewage system. This study investigates the combined quantitative hydrological impact of densification and sustainable stormwater management measures in a residential neighbourhood in Munich, Germany. The living-lab approach pursues the application of nature-based solutions in a real planning case to achieve positive climate effects while densifying the neighbourhood. The study is based on single event simulations of three return periods with the physically based software PCSWMM. The events are implemented for both current and climate change precipitation intensities of the RCP 8.5 projection for 2040–2069. Three scenarios are implemented: a status quo, a business as usual scenario (additional buildings without compensation measures) and a best-case scenario (one additional floor with green roofs disconnected from the sewers in combination with rain gardens and porous pavements on the land parcels). The comparison between the different scenarios focuses on three main aspects of the water balance, namely, infiltration, runoff and storage. The results show that measures for sustainable stormwater management are crucial elements to cope with an increasing number of heavy precipitation events due to climate change. The best-case scenario significantly outperforms the other two concerning water infiltration, surface runoff and storage. Most notably is the impact of climate change projection rainfall intensities for 2040–2069. The outcomes for these intensities clearly show the positive impact of sustainable water-sensitive design. The results demonstrate that it is in fact possible to enhance the water balance and gain new living space simultaneously if a sustainable urban planning strategy is implemented that includes future-oriented stormwater management.

Influence of Blue-Green and Grey Infrastructure Combinations on Natural and Human-Derived Capital in Urban Drainage Planning

The natural capital and ecosystem services concepts describe the multiple benefits people get from nature. Urbanisation has been identified as one of the key factors influencing the decline of natural capital globally. Urbanisation has also been associated with a recent increase in urban flooding incidents in most cities globally. While the understanding of blue-green infrastructure in urban drainage is well established, little is said about its influence on natural capital. This study utilises the Natural Capital Planning Tool, Benefits Evaluation of Sustainable Drainage Systems tool and expert stakeholder interviews to assess the influence of blue-green and grey infrastructure as adaptation pathways in urban drainage, on natural capital and ecosystem services, and to determine how these contribute to other forms of human-derived capital. Key findings show that blue-green options can enhance natural capital and ecosystem services such as amenity value while also contributing to social and human capital. Although the assessed blue-green options contribute to regulating ecosystem services such as floods regulation, their most significant contribution is in cultural ecosystem services, especially amenity value. It is concluded that incorporating blue-green infrastructure in urban drainage adaptive approaches can mitigate natural capital losses and contribute to other forms of capital crucial for human well-being.

Predicting Multiple Properties of Pervious Concrete through the Gaussian Process Regression

Abstract Pervious concrete creates a very porous medium that allows water to penetrate the pavement to underlying soils. It is a promising candidate in permeable pavement systems in urban areas, which could be an efficient solution to sustainable drainage systems. Concrete mixture design usually requires labor-intensive and time-consuming work, which involves a significant amount of “trial batching” approaches. Recently, machine learning methods have demonstrated that a robust model might help reduce the experimental work. Thus, we develop the Gaussian process regression (GPR) model to shed light on the relationship between predictors (nominal coarse aggregate sizes, cement content, water-to-cement ratios, and coarse aggregates content) and each of the different properties (density, compressive strength, tensile strength, and porosity) of pervious concrete. The modeling approach has a high degree of accuracy and stability, contributing to fast, low-cost estimations of multiple properties of pervious concrete.

Quantifying the Impact on Stormwater Management of an Innovative Ceramic Permeable Pavement Solution

Stormwater management in cities has traditionally been based on centralized systems, evacuating runoff as quickly as possible through drainage networks that collect and convey the runoff to the final point of treatment or the receiving water body. In recent years, a different approach focused on the use of Sustainable Urban Drainage Systems (SUDS) represents a paradigm shift, promoting a decentralized management as close to the runoff source as possible. Among these techniques, permeable pavements represent an effective solution for reducing runoff and providing pollutant treatment. This contribution describes the results obtained from an innovative ceramic permeable pavement developed as part of the LIFE CERSUDS project in the city of Benicàssim (Spain). This pavement, composed by modules built from ceramic tiles in stock, allows water infiltration, runoff treatment and water reuse as part of a SUDS built in 2018 and monitored from September 2018 to September 2019. The purpose of the research was to demonstrate the hydraulic performance of the proposed solution through monitoring of runoff quantity and quality variables. Monitoring data analysis have shown positive results, reducing peak runoff rates and the volume of water which is conducted downstream. From the hydrological point of view, the system capacity shown a 100% runoff management for events up to 15–25 mm of precipitation. This is a very significant threshold since these values represent, respectively, the 81% and 91% percentiles for the study area. System performance was confirmed in terms of runoff management and water infiltration. This demonstration case study represents a reference example of urban retrofitting actions which integrate social, economic and environmental aspects.

A Stochastic Procedure for Temporal Disaggregation of Daily Rainfall Data in SuDS Design

Hydrological design of Sustainable urban Drainage Systems (SuDS) is commonly achieved by estimating rainfall volumetric percentiles from daily rainfall series. Nevertheless, urban watersheds demand rainfall data at sub-hourly time step. Temporal disaggregation of daily rainfall records using stochastic methodologies can be applied to improve SuDS design parameters. This paper is aimed to analyze the ability of the synthetic rainfall generation process to reproduce the main characteristics of the observed rainfall and the estimation of the hydrologic parameters often used for SuDS design and by using the generally available daily rainfall data. Other specifics objectives are to analyze the effect of Minimum Inter-event Time (MIT) and storm volume threshold on rainfall volumetric percentiles commonly used in SuDS design. The reliability of the stochastic spatial-temporal model RainSim V.3 to reproduce observed key characteristics of rainfall pattern and volumetric percentiles, was also investigated. Observed and simulated continuous rainfall series with sub-hourly time-step were used to calculate four key characteristics of rainfall and two types of rainfall volumetric percentiles. To separate independent rainstorm events, MIT values of 3, 6, 12, 24, 48 and 72 h and storm volume thresholds of 0.2, 0.5, 1 and 2 mm were considered. Results show that the proposed methodology improves the estimation of the key characteristics of the rainfall events as well as the hydrologic parameters for SuDS design, compared with values directly deduced from the observed rainfall series with daily time-step. Moreover, MITs rainfall volumetric percentiles of total number of rainfall events are very sensitive to MIT and threshold values, while percentiles of total volume of accumulated rainfall series are sensitive only to MIT values.

Sustainable Urban Drainage System Model for The Nhieu Loc – Thi Nghe Basin, Ho Chi Minh City

In recent years, Ho Chi Minh City has been faced with stark challenges in urban flooding affected by the impact of climate change in associated with the rapid urbanization and unadequate urban planning. Although many flood mitigation solutions were invested and implemented such as upgrading drainage systems, transport infrastructure, flood control pumps, etc. the problem remains unsolved and even worse. The purpose of this study is to propose a calculation model of the sustainable urban drainage system (SuDS) integrated with of GIS and remote sensing technology to assess and predict flooding degree in a specific basin in HCMC. Further, the results of this calculation model are just a pre-testing and pre-simulation of the proposed model for future studies on the application of sustainable urban drainage techniques, including rainwater harvesting, green roofs, urban green space and pervious pavement.

Assessing the performance of gray and green strategies for sustainable urban drainage system development: A multi-criteria decision-making analysis

The performance assessment of a sustainable urban drainage system (SUDS) involves multiple criteria and is important for the decision-making of urban sustainable development. In this study, we intend to balance the comprehensiveness and objectivity in the performance assessment of SUDS development through a combination of multi-criteria decision-making (MCDM) analysis and mathematical quantification. We proposed an MCDM framework with eight quantifiable indicators, including flood mitigation capacity, pollution control capacity from technical criteria, life-cycle cost, damage cost, recreational function from socioeconomic criteria, biotope area ratio from ecological criteria, and spatial consistency from political criteria. A city-scale model based on engineering datasets and satellite images was created to implement gray and green infrastructure strategies in the studied area. Results revealed that gray strategies performed better in hydraulic improvements, mitigating approximately 17% of flood magnitude and decreasing over 20% of flood-induced damage. Green strategies were more eco-friendly, removing approximately 60% of non-point pollution and improving at most 15% of the ecological level. Integrated assessment demonstrated that the combine-used strategy showed the overall best performance, with a sustainability index of 0.676. Therefore, the methods and results in this study could provide additional improvements in the decision-making process of SUDS development.

Vegetation Survival in Green Roofs without Irrigation

The implementation of green roofs as sustainable urban drainage systems provides benefits for stormwater control and the environment and is more and more encouraged. A model for the estimation of the probability of vegetation survival without irrigation is proposed. The model, developed through a probabilistic analytical derivation procedure, can also consider the effects of chained rainfall events, without the need of continuous simulation of hydrological processes. The model equations can be useful in the design of green roofs, allowing to determine the growing medium thickness in terms of an assumed risk of vegetation withering in dry periods. The proposed model is also able to identify the optimal thickness of the growing medium, over which the survival performances can be increased only with irrigation. Model performances were tested by the application to two case studies in Italy. Comparison between the probabilities and the cumulative frequencies from a continuous simulation of water content in the growing medium shows a good agreement and provide a first confirmation of reliability.

Root causes of failures in sustainable urban drainage systems (SUDS): an exploratory study in 11 municipalities in The Netherlands

Abstract Despite being widely implemented, sustainable urban drainage systems (SUDS) do not always function flawlessly. While SUDS have been tested extensively and seem to perform well on a laboratory or pilot scale, practitioners' experience is different: failures in SUDS occur regularly in practice, resulting in malfunctioning systems, water nuisance and high costs. To anticipate their malfunctioning, and thus to improve their performance, a better understanding of failures occurring in SUDS and their underlying causes is needed. Based on an explorative case-study approach, consisting of site visits and semi-structured interviews with urban water professionals, this study presents an inventory of technical failures in SUDS and an analysis of their root causes. In total, 70 cases in 11 Dutch municipalities have been documented. The results show that the interfaces between SUDS and other urban systems are prominent failure locations. In addition, we found that failures originate from the entire development process of SUDS, i.e., from the design, construction and user/maintenance phase. With respect to the causes underlying these failures, our results show that these are mainly socio-institutional in nature. These are valuable insights for both practitioners and scholars, contributing to a renewed socio-technical urban water system with more sustainable water management practices.

The effect of urban development on runoff volumes in the London Borough Barking and Dagenham

Estuarine and coastal areas have always had an issue with regard to an increased level of flood hazards. In addition, since urban developments have an impact on water runoff, future house building plans and new decisions to prevent flooding are essential. The peak rate of runoff is greater for a developed site than it was for the pre-development sit and flood recovery of developed sites requires more time. Therefore, it is crucial to ensure that future developments do not worsen flooding problems. The London Borough of Barking and Dagenham (LBBD) is an example of an area in the north-east corner of London, on the north bank of the River Thames which is currently undergoing major developments. The runoff coefficient as calculated by the Wallingford modified rational method, the geographic information system, and the core strategy in the LBBD illustrated that there was an increase in the peak runoff discharge by about 29.4% following developments. The use of sustainable urban drainage systems and other feasible mitigations such as drainage systems could reduce the risk of flooding as a result of surface water runoff.

Procedures of engineering geological mapping applied to urban planning in a data-scarce area: Application in southern Brazil

Resultsfrom an engineering geological mapping study of the urban area of Ouro Preto in the state of Minas Gerais, Brazil, are presented. The goal of the study was to verify the efficacy of procedures, methods and classification schemes based on engineering geological mapping principles to generate data and maps for urban planning, restructuring (rehabilitation) and engineering projects. The study was developed at a 1:10,000 scale and based on field and laboratory studies and on the analysis and interpretation of aerial photography and satellite images. The selected study area has been urbanized for over 300 years and requires territorial planning and reorganization of land uses. The area is composed of highly variable rock types, unconsolidated materials and terrain features. Data collection and mapping were performed to identify and delineate 51 engineering geological units in terms of the spatial distribution of geological materials, genetic characteristics, mineralogy, the estimated strength, hydraulic conductivity interfaces and potential failure surfaces. All units were assessed in terms of excavatability conditions, predisposition to erosion and shallow translational landslide, suitability for sustainable urban drainage systems (SUDS), contaminant flow conditions, potential use as construction materials and foundation-related aspects. Recommendations for a detailed site investigation were made, and the suitability of geological materials for engineered fill was evaluated. A constraint zoning analysis was carried out to contextualize urban planning. The adopted procedures, methods and classification schemes were shown to be efficient when implemented in conjunction with intensive field studies and enabled the delineation of units with different engineering geological characteristics that are important for urban planning involving different users.

Not all SuDS are created equal: Impact of different approaches on combined sewer overflows

Sustainable urban drainage systems (SuDS) help in stormwater management by reducing runoff volume, increasing runoff concentration time and thereby improving the drainage system capacity. This study investigated the potential and cost-effectiveness of SuDS in reducing combined sewer overflows (CSOs). We simulated the performance of four SuDS techniques (bioretention cell, permeable pavement, rain barrel and green roof) at incremental levels of spatial coverage for a small urban catchment with a combined sewer system. We also used an Analytic Hierarchy Process (AHP) considering end-point CSO, land use, imperviousness, slope and elevation criteria to identify priority areas for SuDS deployment. Results showed that CSO volume attenuation ranged a maximum of 50–99% for the catchment, depending on the deployment strategy and underlying mechanisms of each technology. We also found that deployment of SuDS in AHP-selected sub-catchments improved CSO reduction only for rain barrels and green roofs, but not for bioretention cells and permeable pavements. SuDS were also a cost-effective retrofit option: for a 40% volume reduction, the SuDS cost, at most, 25% of the equivalent cost required for a large CSO tank. Outcomes of this study demonstrate the efficacy of SuDS in controlling CSOs, adding yet another tangible benefit to their increasingly recognised multi-functionality.

Experimenting Transition to Sustainable Urban Drainage Systems—Identifying Constraints and Unintended Processes in a Tropical Highly Urbanized Watershed

Green Infrastructure promotes the use of natural functions and processes as potential solutions to reduce negative effects derived from anthropocentric interventions such as urbanization. In cities of Latin America, for example, the need for more nature-based infrastructure is evident due to its degree of urbanization and degradation of ecosystems, as well as the alteration of the local water cycle. In this study, an experimental approach for the implementation of a prototype is presented. The prototype consists of a gray-hybrid element for first flush bio-treatment and runoff detention, adapted to the existing stormwater sewer. The experiment took place in a highly urbanized watershed located in the Metropolitan Area of Costa Rica. The characteristics of the existing infrastructure in the study area at different scales were mapped and compared using the Urban Water System Transition Framework. Subsequently, preferences related to spatial locations and technologies were identified from different local decision-makers. Those insights were adopted to identify a potential area for the implementation of the prototype. The experiment consisted of the adaptation of the local sewer to act as a temporal reservoir to reduce the effects derived from rapid generation of stormwater runoff. Unexpected events, not considered initially in the design, are reported in this study as a means to identify the necessary adaptations of the methodology. Our study shows from an experimental learning-experience that the relation between different actors advocating for such technologies influences the implementation and operation of non-conventional technologies. Furthermore, the willingness of residents to modify their urban environments was found to be associated to their own perceptions about security and vandalism occurring in green spaces. The implementation of the prototype showed that both the hydraulic performance is relevant for considering it as a success, as well as the dynamics of the adapted element with the existing urban conditions. In consequence, those aspects should be carefully considered as the design factors of engineering elements when they are related to complex socio-ecological urban systems.

Infiltration Capacity of Rain Gardens Using Full-Scale Test Method: Effect of Infiltration System on Groundwater Levels in Bergen, Norway

The rain gardens at Bryggen in Bergen, Western Norway, is designed to collect, retain, and infiltrate surface rainfall runoff water, recharge the groundwater, and replenish soil moisture. The hydraulic infiltration capacity of the Sustainable Drainage System (SuDS), here rain gardens, has been tested with small-scale and full-scale infiltration tests. Results show that infiltration capacity meets the requirement and is more than sufficient for infiltration in a cold climate. The results from small-scale test, 245–404 mm/h, shows lower infiltration rates than the full-scale infiltration test, with 510–1600 mm/h. As predicted, an immediate response of the full-scale infiltration test is shown on the groundwater monitoring in the wells located closest to the infiltration point (<30 m), with a ca. 2 days delayed response in the wells further away (75–100 m). Results show that there is sufficient capacity for a larger drainage area to be connected to the infiltration systems. This study contributes to the understanding of the dynamics of infiltration systems such as how a rain garden interacts with local, urban water cycle, both in the hydrological and hydrogeological aspects. The results from this study show that infiltration systems help to protect and preserve the organic rich cultural layers below, as well as help with testing and evaluating of the efficiency, i.e., SuDS may have multiple functions, not only storm water retention. The functionality is tested with water volumes of 40 m3 (600 L/min for 2 h and 10 min), comparable to a flash flood, which give an evaluation of the infiltration capacity of the system.

Factors impacting community’s prioritization towards the benefits of Sustainable Urban Drainage Systems: A case study of Nhieu Loc – Thi Nghe sub-basin, Ho Chi Minh City

Sustainable Urban Drainage System (SUDS) includes various drainage techniques designed to reduce the run-off flow, improve the water quality, and provide amenity or landscape features. However, selecting the appropriate SUDS technique depends on not only the technical characteristics but also the community's perception and preference. Therefore, this study aims to determine the impact factors on the probability of households' prioritization towards SUDS benefits in the context of Nhieu Loc - Thi Nghe sub-basin, including the benefits of flood reduction, environmental enhancement, and landscape improvement. Data processing methods used in this study consist of statistical tests and ordinal regression using SPSS software. The regression results show that the overall accurate prediction rate for the 3 priority levels of SUDS benefits ranges from 50% to 70%. Factors that statistically significantly influence the priority include household income, knowledge of SUDS, frequency of flooding, depth of flooding, the distance to the nearest park, the distance to the nearest water body, and the distance to the nearest flooded location. In particular, the proximity to the nearest park affects the priority choice for all SUDS benefits with the principle that households near the park will probably choose higher priority to SUDS benefits than those living further.

Low impact development strategies for a low-income settlement: Balancing flood protection and life cycle costs in Brazil

Due to economic, environmental, and other wider social issues, implementing sustainable urban drainage systems in developing countries is particularly complex. This study aimed to assess the adoption of low impact development (LID) strategies for a low-income settlement in São Carlos, Brazil, with the additional challenges presented by high-density, small lots, and social-economic constraints. A life cycle cost (LCC) analysis was conducted along with hydrological modeling for three scenarios. The business-as-usual (BAU) scenario: typical urban design and conventional drainage system (CDS). The infiltration well (IW) scenario: typical urban design and CDS associated with lots disconnection with IWs. The LID scenario: infiltration devices (swales and swale-trenches) associated with urban changes to achieve 100 % of runoff source control. A sensitivity analysis was carried out considering variations in the maintenance routine. The LCC revealed that the IW scenario had the higher overall costs: 15 % higher than BAU, and 5–22 % than LID. However, when the scenarios were assessed using a performance-based unit (costs/locally managed stormwater volume), the perspective changed: the LID scenario costs were the lowest (271–507 USD/m³), and BAU were the highest (926–1487 USD/m³). This joint assessment is expected to better assist the decision-making processes for sustainable stormwater management, balancing flood protection and costs.

A Study of Filter Drain Performance for the Pollution Control of Urban Runoff (Dept.C)

Construction, vehicular traffic and maintenance of highway surfaces are sources of pollutants, which accumulate on highway surfaces and other roadside areas. During rainfall runoff events these pollutants are washed from these surfaces and flow to surface and subsurface waters. This research is a study to assess the ability of a constructed filter drain as one of Sustainable Urban Drainage Systems (SUDS) in removing suspended solids, petroleum hydrocarbons, metals in the form of Copper and Zinc and polycyclic aromatic hydrocarbons were used for the present study from urban runoff. The constructed filter drain was successful in controlling, attenuating and treating runoff containing pollutant loadings of (sediments, petroleum hydrocarbons, metals and polycyclic aromatic hydrocarbons). For the eight stimulated test runs, the average removal rate of the builder's sand as sediments was 97%. The average total petroleum hydrocarbon removing rate was 97 .8%. The mean copper (Cu) and zinc (Zn) removing rate was 82% and 92% respectively. The average removing rate of polycyclic aromatic hydrocarbons