Sustainable Drainage Systems Research Articles

The use of karst geomorphology for planning, hazard avoidance and development in Great Britain

Within Great Britain five main types of karstic rocks – dolomite, limestone, chalk, gypsum and salt – are present. Each presents a different type and severity of karstic geohazard which are related to the rock solubility and geological setting. Typical karstic features associated with these rocks have been databased by the British Geological Survey (BGS) with records of sinkholes, cave entrances, stream sinks, resurgences and building damage; data for more than half of the country has been gathered. BGS has manipulated digital map data, for bedrock and superficial deposits, with digital elevation slope models, superficial deposit thickness models, the karst data and expertly interpreted areas, to generate a derived dataset assessing the likelihood of subsidence due to karst collapse. This dataset is informed and verified by the karst database and marketed as part of the BGS GeoSure suite. It is currently used by environmental regulators, the insurance and construction industries, and the BGS semi-automated enquiry system. The database and derived datasets can be further combined and manipulated using GIS to provide other datasets that deal with specific problems. Sustainable drainage systems, some of which use soak-aways into the ground, are being encouraged in Great Britain, but in karst areas they can cause ground stability problems. Similarly, open loop ground source heat or cooling pump systems may induce subsidence if installed in certain types of karstic environments such as in chalk with overlying sand deposits. Groundwater abstraction also has the potential to trigger subsidence in karst areas. GIS manipulation of the karst information is allowing Great Britain to be zoned into areas suitable, or unsuitable, for such uses; it has the potential to become part of a suite of planning management tools for local and National Government to assess the long term sustainable use of the ground.

Briefing: Keeping up with the Suds revolution and legislative evolution

The past ten years has seen progressive integration of sustainable drainage systems into the fabric of development and planning policy across the UK. With increasing urbanisation, exceptional flood events and the potential changes in our climate behaviour, there is a need for careful management of surface water and consideration of its quantity, quality and a symbiotic need to combine this with amenity and biodiversity within a hardening, simplified environment. From the implementation of the water framework directive, through to the recent implementation of the Flood and Water Management Act, sustainable drainage systems have evolved from a conceptual, novel idea to a design of principal importance for most new developments. This paper reviews the progression of sustainable drainage systems from a little-applied soft drainage technique to an essential feature of flood risk assessments and planning policy through responsive and strategic legislative development that also lead to new roles for all flood management authorities.

Runoff infiltration, a desktop case study

The use of sustainable drainage systems (SuDS) or best management practice is becoming increasingly common. However, rather than adopting the preferred 'treatment train' implementation, many developments opt for end-of-pipe control ponds. This paper discusses the use of SUDS in series to form treatment trains and compares their potential performance and effectiveness with end-of-pipe solutions. Land-use, site and catchment characteristics have been used alongside up-to-date guidance, Infoworks CS and MUSIC to determine whole-life-costs, land-take, water quality and quantity for different SuDS combinations. The results presented show that the use of a treatment train allows approaches differing from the traditional use of single SuDS, either source or 'end-of-pipe', to be proposed to treat and attenuate runoff. The outcome is a more flexible solution where the footprint allocated to SUDS, costs and water quality can be managed differently to fully meet stakeholder objectives.

Valuing amenity: public perceptions of sustainable drainage systems ponds

AbstractUnderstanding the potential concerns and needs of residents is key to achieving good acceptability of sustainable drainage systems (SuDS). This paper highlights, through the application of a structured questionnaire, the potential value to residents of living in close proximity to a SuDS pond. The results show that although the pond's characteristics are not the main factor influencing the choice to move into an area, its effect is markedly positive. Contingent valuation of the benefits is used to show that the additional value brought by SuDS amenity, when monetised, can offset a pond's initial construction costs and ongoing maintenance, hence ensuring the return on investment for developers. By building on existing research, this paper highlights major changes in the perception and valuation of pond structures.

The spread of sustainable urban drainage systems for managing urban stormwater: A multi-level perspective analysis

Following the Brundtland Commission in 1987 (United Nation, 1987), numerous reports have condemned the impact of human activities on the environment, with the result that “sustainable development” has become a major issue for society. The move towards creating more sustainable cities, as described in the New Charter of Athens (ECTP, 2003), is a clear reflection of these concerns. The present article examines this final category of alternative techniques, focusing on urban stormwater management systems, which are designed to avoid the problems rainwater runoff can cause in urban environments, such as erosion of urban surfaces, floods, traffic disruption, and disruption to urban activities in general. More precisely, the barriers of uptake of innovation for sustainability in urban stormwater management systems are discussed.JEL Codes: Q01, Q25, R, L32, H75

Analysis and Contrast of Different Pervious Pavements for Management of Storm-Water in a Parking Area in Northern Spain

Pervious pavements are rainwater control systems that filter and store rainwater, reducing runoff formation and the risk of urban flooding. In addition, these sustainable urban drainage systems provide an additional source of water for non-potable use, which implies a cost and energy saving. An experimental 45 place parking lot consisting of five different types of pervious pavements was constructed in a public park in Santander, northern Spain. The purpose of this research is to evaluate and compare the effect of each pervious pavement type on water storage under specific conditions in northern Spain over time. The main results showed that the pervious materials chosen influence the behaviour of pervious pavements for storm-water management. Firstly, pervious surface materials had a greater effect than the geotextile layer. Nevertheless, the differences in terms of storm-water management using the different pervious pavement types tested still need to be confirmed. Clustering techniques showed three different behaviours according to the pervious surface used. Moreover, porous asphalt (PA) and porous concrete (PC) showed the highest correlation (86%), whereas plastic grid pavers (PGC) showed least correlation with the others. The capacity of pervious pavement to manage urban storm-water was demonstrated and this experimental parking area provided an alternative water source supplying enough water to irrigate a public garden for almost an entire month.

Doing the first loop of planning for sustainable urban drainage system retrofits: A case study from Odense, Denmark

The planning and implementation of sustainable urban drainage systems (SUDS) requires intensive collaboration between professions and institutions. To improve the conditions for such practice in Denmark, the first loop of a SUDS-based retrofitting project was completed in Odense over a 6-month period. The project involved officials from the City of Odense and Odense Water Ltd., as well as university researchers. Studies of hydrological, environmental and socio-cultural aspects were developed by disciplinary teams and used to draft integrated solutions for two selected city districts. Albeit sewer surcharge was the initial catalyst, the main driver for the drafted solutions was urban planning. An assessment of the impact 1.5 years after completion indicated that the employed approach is valuable. In Odense, a planning procedure reflecting the loop process has become new practice. The project represents a key reference for the introduction of SUDS in Denmark.

Combining multimedia models with integrated urban water system models for micropollutants

Integrated urban water system (IUWS) modeling aims at assessing the quality of the surface water receiving the urban emissions through sewage treatment plants, combined sewer overflows (CSOs) and stormwater drainage systems. However, some micropollutants tend to appear in more than one environmental medium (air, water, sediment, soil, groundwater, etc.). In this work, a multimedia fate and transport model (MFTM) is "wrapped around" a dynamic IUWS model for organic micropollutants to enable integrated environmental assessment. The combined model was tested on a hypothetical catchment using two scenarios: on the one hand a reference scenario with a combined sewerage system and on the other hand a stormwater infiltration pond scenario, as an example of a sustainable urban drainage system (SUDS). A case for Bis(2-ethylhexyl) phthalate (DEHP) was simulated and resulted in reduced surface water concentrations for the latter scenario. However, the model also showed that this was at the expense of increased fluxes to air, groundwater and infiltration pond soil. The latter effects are generally not included in IUWS models, whereas MTFMs usually do not consider dynamic surface water concentrations,; hence the combined model approach provides a better basis for integrated environmental assessment of micropollutants' fate in urban environments.

Guidance on variables characterising water bodies including sustainable flood retention basins

Climate change is likely to increase the frequency of flood events, thus increasing the associated hazard. This may threaten some existing flood defences, which were designed and built prior to climate change being identified as a major issue; therefore, they may require modification to ensure their sustainability. The European Union recognises that member states may face significant challenges in implementing the Flood Directive and has responded with programs such as the Strategic Alliance for Water Management Actions, which aims to provide tools and guidance to aid the member states in implementation. Flooding is a complex spatial planning issue and therefore requires a range of tools and approaches to solve the problem. Solutions are likely to require sustainable (urban) drainage system (SUDS) solutions applied on a small scale combined with sustainable flood retention basins (SFRB) used on a large scale. This paper aims to provide guidance on 40 variables used to rapidly assess water bodies including SFRB in terms of their flood and diffuse pollution control purposes and potentials. The variables described should be the basis for the characterisation of SFRB, which are adaptive structural measures well integrated within the landscape promoting best management practice as part of a sustainable flood risk management strategy. The variables engineered, outlet arrangement, aquatic animal passage, land animal passage, basin and channel connectivity, seasonal influence, relative total pollution and flotsam cover are novel. The list includes sum parameter such as relative total pollution, which address as part of a simplified methodology several complex environmental processes.

Optimising regional sustainable drainage systems pond performance using treatment trains

The use of sustainable drainage systems (SuDS) or best management practice (BMP) is becoming increasingly common. However, rather than adopting the preferred “treatment train” implementation, many developments opt for end-of-pipe control ponds. This paper discusses the use of SuDS in series to form treatment trains and compares their potential performance and effectiveness with end-of-pipe solutions. Land use, site and catchment characteristics have been used alongside up-to-date guidance, Infoworks CS and the model for urban stormwater improvement conceptualisation to determine whole-life-costs, land take, water quality and water quantity for different SuDS combinations. The results presented show that the use of a treatment train allows approaches differing from the traditional use of single SuDS, either source or “end-of-pipe”, to be proposed to treat and attenuate runoff. This outcome provides a more flexible solution where the footprint allocated to SuDS, costs and water quality can be managed differently to more comprehensively meet stakeholder objectives.

Appropriate drainage systems for a changing climate

Sustainable drainage systems are increasingly seen as a better way of draining urban areas, being ‘more natural’, less resource intensive and offering water quantity and quality control with amenity benefits. Sustainable drainage systems ‘greening’ can also reduce heat island effects. However, little attention has been given to assessing the real value and sustainability of the approach and uncertainties remain over performance and robustness, as well as ownership and maintenance. Received wisdom suggests that sustainable drainage systems have potential to help cope with climate change, while offering wider sustainability benefits over traditional piped drainage. The inherent adaptability of sustainable drainage systems allows them to be implemented incrementally as climate change knowledge advances. This paper provides evidence from a range of initiatives to show how sustainable drainage systems can contribute to a portfolio approach to tackling the problems of climate change. The need for political intervention and enhanced stakeholder engagement to support this type of approach is highlighted.

Adjusting soil infiltration coefficients for groundwater level

Current UK guidance for the design of sustainable drainage systems recommends that infiltration devices, such as soakaways, permeable pavements and infiltration basins, should be able to operate during periods of extreme groundwater level. Furthermore, higher groundwater levels have recently been shown to cause a reduction in the empirical soil infiltration coefficient, as used in the design of infiltration devices. However, there is currently no simple method available to estimate the required reduction in the design infiltration coefficient to account for an extreme groundwater level. This paper uses exploratory numerical subsurface saturated–unsaturated hydrological modelling to quantify the effect of groundwater level on the infiltration coefficient for six typical soil types. The fixed resolution finite-element simulations are also benchmarked against a solution employing adaptive mesh refinement. The modelling results are distilled into charts and a simple equation to allow the calculation of adjustment factors, with which to reduce the design infiltration coefficient to account for a higher design groundwater level. Varying soil type sensitivity is highlighted. These factors could also be used to correct for soakage tests made during periods of lower groundwater level. Threshold depths to groundwater, below which no adjustment is required, are identified for each soil type.

SWITCH in Belo Horizonte, Brazil: infiltration and detention systems for more sustainable stormwater control in Belo Horizonte

Belo Horizonte, Brazil, is one of the demonstration cities of the SWITCH project. Flooding and wet weather pollution are major issues for the city. Because of this SWITCH in Belo Horizonte has focussed on more sustainable urban drainage systems (SUDS). Demonstrations are being conducted of infiltration and detention devices, artificial wetlands, and rainfall harvesting. This paper focuses on the use of detention and infiltration trenches to control runoff and abate wet weather pollution. Preliminary results indicate that use of these devices have potential for significantly mitigating suspended matter such as heavy metals originating from road surfaces.

Urban Storm-Water Quality Management: Centralized versus Source Control

The continuous growth of urban areas and the increasing public awareness of the environmental impacts of storm water have raised interest on the quality of the receiving water bodies. In the past two decades, many efforts have been directed at improving urban drainage systems by introducing mitigation measures to limit the negative environmental impacts of storm water. These mitigation measures are generally called best management practices (BMPs), sustainable urban drainage systems, or low impact developments, and they include practices such as infiltration and storage tanks that reduce the peak flow and retain some of the polluting materials. Choosing the best mitigation measure is still a controversial topic. To gain insight on the best technique, this study compares different distributed and centralized urban storm-water management techniques, including infiltration and storage facilities. The main objective of this study is to use modeling to assess the effects of the different urban drainage techniques. To this end, a homemade model that was developed in previous studies is applied. This model enables us to simulate both combined sewer systems and ancillary structures such as storm tanks or infiltration trenches to determine water quantity and quality characteristics. A long-term simulation is employed to account for the effects of sediments in BMPs, which generally reduce the hydraulic capacity. The results allow us to draw some conclusions on the peculiarities of BMP techniques, on the possibility of integrating different techniques for improving efficiency, and on BMP maintenance planning.

The best management of SuDS treatment trains: a holistic approach

The use of Sustainable Drainage Systems (SuDS) or Best Management Practice (BMP) is becoming increasingly common. However, rather than adopting the preferred "treatment train" implementation, many developments opt for end of pipe control ponds. This paper discusses the use of SuDS in series to form treatment trains and compares their potential performance and effectiveness with end of pipe solutions. Land-use, site and catchment characteristics have been used alongside up-to-date guidance, Infoworks CS and MUSIC to determine whole-life-costs, land-take, water quality and water quantity for different SuDS combinations. The results presented show that the use of a treatment train allows approaches differing from the traditional use of single SuDS, either source or "end of pipe", to be proposed to treat and attenuate runoff. The outcome is a more flexible solution where the footprint allocated to SuDS, costs and water quality can be managed differently to satisfy more efficiently the holistically stakeholders' objectives.

Soakage testing: modelling the effect of antecedent hydrology

Current design methods for sustainable drainage system infiltration devices such as soakaways, permeable pavements and infiltration basins require knowledge of the empirical soil infiltration coefficient, which is determined using a soakage test procedure. However, the control that seasonal antecedent hydrological conditions, specifically unsaturated zone soil moisture and water table position, have on the infiltration coefficient is uncertain. This paper uses exploratory numerical modelling to investigate this uncertainty. The results show that antecedent water table position has a significant effect on the infiltration coefficient, while for a properly conducted test the seasonal antecedent soil moisture is less important. To avoid overestimating the infiltration coefficient, soakage testing should ideally be performed under the most onerous hydrological conditions and three successive drain downs must be used. Model outputs such as those presented can be used to reduce the design infiltration coefficient to account for tests made during periods of lower groundwater level and higher design water table positions. Additionally, the current infiltration coefficient calculation is shown to be biased towards the initial, more rapid, infiltration rate. Therefore, an alternative full-depth infiltration coefficient calculation is proposed. Finally, a potential detrimental feedback is hypothesised between infiltration device performance and groundwater mounding. Significant design implications are discussed.

Stormwater infiltration trenches: a conceptual modelling approach

In recent years, limitations linked to traditional urban drainage schemes have been pointed out and new approaches are developing introducing more natural methods for retaining and/or disposing of stormwater. These mitigation measures are generally called Best Management Practices or Sustainable Urban Drainage System and they include practices such as infiltration and storage tanks in order to reduce the peak flow and retain part of the polluting components. The introduction of such practices in urban drainage systems entails an upgrade of existing modelling frameworks in order to evaluate their efficiency in mitigating the impact of urban drainage systems on receiving water bodies. While storage tank modelling approaches are quite well documented in literature, some gaps are still present about infiltration facilities mainly dependent on the complexity of the involved physical processes. In this study, a simplified conceptual modelling approach for the simulation of the infiltration trenches is presented. The model enables to assess the performance of infiltration trenches. The main goal is to develop a model that can be employed for the assessment of the mitigation efficiency of infiltration trenches in an integrated urban drainage context. Particular care was given to the simulation of infiltration structures considering the performance reduction due to clogging phenomena. The proposed model has been compared with other simplified modelling approaches and with a physically based model adopted as benchmark. The model performed better compared to other approaches considering both unclogged facilities and the effect of clogging. On the basis of a long-term simulation of six years of rain data, the performance and the effectiveness of an infiltration trench measure are assessed. The study confirmed the important role played by the clogging phenomenon on such infiltration structures.

Evidence of traffic-related pollutant control in soil-based Sustainable Urban Drainage Systems (SUDS)

SUDS are being increasingly employed to control highway runoff and have the potential to protect groundwater and surface water quality by minimising the risks of both point and diffuse sources of pollution. While these systems are effective at retaining polluted solids by filtration and sedimentation processes, less is known of the detail of pollutant behaviour within SUDS structures. This paper reports on investigations carried out as part of a co-ordinated programme of controlled studies and field measurements at soft-engineered SUDS undertaken in the UK, observing the accumulation and behaviour of traffic-related heavy metals, oil and PAHs. The field data presented were collected from two extended detention basins serving the M74 motorway in the south-west of Scotland. Additional data were supplied from an experimental lysimeter soil core leaching study. Results show that basin design influences pollutant accumulation and behaviour in the basins. Management and/or control strategies are discussed for reducing the impact of traffic-related pollutants on the aqueous environment.

The potential of green roofs to manage Urban Stormwater

Green roofs have considerable potential for stormwater source control, both for new developments and as a retrofit option. In the United Kingdom the lack of local quantitative performance data and modelling tools, together with more general barriers to sustainable drainage systems (SUDS) implementation, may explain their limited uptake to date. This paper presents preliminary findings from a small-scale instrumented green roof test plot located in Sheffield, UK. During spring 2006 the average volume retention was 34% and the average peak reduction was 57%. The key hydrological determinants were the antecedent dry weather period (ADWP), mean rainfall intensity and rainfall depth. Detailed examination of rainfall–runoff relationships in summer 2007 demonstrates the dependency of performance on antecedent moisture conditions. Structural appraisal of a range of flat roof types suggests that retrofitting a green roof will be a feasible option in many cases, particularly for concrete slab roofs.

Sustainable Urban Drainage Systems (SUDS) treatment train assessment tool

This paper outlines a rationale and scoring system for the stormwater treatment train assessment tool (STTAT) which is a proposed regulatory tool for Sustainable Urban Drainage Systems (SUDS). STTAT provides guidance and regulatory consistency for developers about the requirements of planners and the Scottish Environment Protection Agency (SEPA). The tool balances the risks of pollution to the receiving water body with the treatment provided in a treatment train. It encourages developers to take SUDS into account early, avoiding any misunderstanding of SUDS requirements at the planning stage of a development. A pessimistic view on pollution risks has been adopted since there may be a change of land use on the development in the future. A realistic view has also been taken of maintenance issues and the 'survivability' of a SUDS component. The development of STTAT as a response to the requirements of the Water Framework Directive is explored, the individual scores being given in tabular format for receiving water and catchment risks. Treatment scores are proposed for single SUDS components as well as multiple components within treatment trains. STTAT has been tested on a range of sites, predominantly in Scotland where both development and receiving water information was known. The operational tool in use by SEPA is presented.