Commended
Harnessing Sustainable Urban Drainage Systems (SuDS) for Surface Water Management
Words by Billy Cripps, Nottingham Trent University
Urbanisation over the last century has significantly altered natural landscapes, leading to a decrease in permeable surfaces and an increase in surface water runoff. This, in turn, raises the risk of urban flooding, which has become a prominent challenge in many areas. In the UK alone, flooding causes between £500 million and £1 billion in damages annually, a figure that is projected to rise with the added pressures of climate change. Sustainable Urban Drainage Systems (SuDS) offer a solution to this problem, managing surface water runoff by mimicking natural drainage processes.
This Report explores the potential of SuDS to minimise surface water runoff on the author’s Major Study Project (MSP) site, located near the River Derwent, which faces recurring risks of pluvial flooding. The study evaluates different SuDS configurations using both qualitative and quantitative research methods to determine the most effective solution for managing surface water on the site. The use of Architectural Technology was integral to this research, particularly in the design and modelling of SuDS systems.
Methodology
A mixed-methods approach was employed, integrating qualitative and quantitative data collection to provide a comprehensive evaluation of the selected SuDS configurations. The study was divided into three phases:
Phase 1: Critical Literature Review – This phase involved reviewing 13 journal articles published within the last 15 years to ensure the research was current. The review focused on two key themes: comparing five types of SuDS based on their water retention and pollution reduction values, and identifying the most suitable algorithm for calculating the QBAR (Mean Annual Flood) for the MSP site. From this review, bioretention cells, green roofs, and permeable paving were selected for further testing due to their high water retention and pollution reduction capabilities.
Phase 2: Site-Specific Data Analysis – The UK SuDS Greenfield Runoff Rate Estimation tool was used to gather hydrological data specific to the MSP site. The IH124 algorithm was selected to calculate the QBAR, which provided the baseline runoff value used for comparison in the simulations.
Phase 3: Storm Water Management Model (SWMM) – In this phase, the SWMM software was used to simulate storm events and assess the performance of each SuDS configuration. Rainfall data from historic weather reports was used to simulate a 1 in 100-year storm event, and various combinations of SuDS were tested to determine their effectiveness in reducing surface water runoff.
Application of Architectural Technology
The integration of Architectural Technology was crucial in both the design and evaluation of each SuDS strategy. The Building Information Modeling (BIM) software, Revit, was used to model each SuDS configuration, allowing for detailed design and visualization of the systems before they were inputted into SWMM for simulation. This ensured that the SuDS systems were tailored to the specific constraints of the MSP site, maximising their effectiveness in reducing surface water runoff. The use of SWMM allowed for a comprehensive analysis of how each SuDS system performed under simulated storm conditions.
SuDS tested
Green roofs
The study tested two green roofs, both modelled in Revit before being inputted into SWMM. The Bauder Turfed Intensive Green Roof, selected for its high water retention capabilities and lightweight structure, was modelled with a 100mm substrate layer and a 50mm water retention and drainage layer. Simulation results showed that the first green roof (GR1) achieved the highest individual retention rate, due to its extensive coverage on the site.
Bioretention cells
A Silva Cell system was chosen for the MSP site, with a design that incorporated 450mm of soil and 300mm of aggregate storage. The modular design of the Silva Cell made it ideal for urban sites where space is limited. The results showed that bioretention cells achieved the highest retention rate per square metre, making them the most effective SuDS solution in space-constrained urban areas.
Permeable paving
Permeable paving was also modelled and tested. While it had a lower individual retention rate compared to green roofs and bioretention cells, it played a vital role when integrated with other SuDS systems.
Results and analysis
The simulation results demonstrated that combining all three SuDS configurations—green roofs, bioretention cells, and permeable paving—achieved a retention rate of 81% during a 1 in 100-year storm. This confirmed the effectiveness of using a SuDS management train approach, where multiple SuDS systems are layered to enhance water retention and pollutant filtration. The results support the conclusion that using a combination of SuDS is more effective than relying on individual systems, disproving the report’s initial hypothesis. The bioretention cells were found to be the most effective individual SuDS per square metre, aligning with findings from other studies, such as Hua et al. (2020) and Joksimovic and Alam (2014). These studies similarly identified bioretention cells as being particularly effective in urban environments with limited space. In contrast, green roofs exhibited high retention rates due to their larger coverage, but required more space to achieve these results. When compared with other research, some discrepancies were noted. For example, Joksimovic and Alam (2014) found that permeable paving had a higher retention rate than green roofs, a finding that differs from the results of this study. These variations highlight the importance of conducting site-specific simulations, as local conditions such as climate and soil type can significantly impact SuDS performance.
Conclusion
The results of this study highlights the importance of using multiple SuDS systems to maximise surface water retention. A combination of green roofs, bioretention cells, and permeable paving was shown to reduce surface water runoff by up to 81%, making it a highly effective strategy for managing stormwater in urban environments. The results also support the conclusion that bioretention cells are the most efficient SuDS per square metre, particularly in space constrained urban areas. Although the SWMM simulations provided valuable insights into the effectiveness of these systems, they did not account for long-term maintenance. Previous research, such as Ahiablame et al. (2012), has highlighted the importance of maintaining SuDS systems to prevent clogging and ensure long-term effectiveness. Future research should focus on the long-term performance of SuDS systems, particularly in relation to maintenance costs and potential system degradation.
In summary, this study confirms that combining SuDS systems significantly improves surface water management, particularly in urban areas. The use of Architectural Technology, including BIM software and SWMM, played a crucial role in designing, modelling, and evaluating these systems, ensuring their effectiveness in reducing flood risk on the MSP site.
Judges' comments
Billy’s Report explores what is a very important topic for the Architectural Technologist and one of much broader social relevance. The thorough introduction to the subject highlights the importance of this study, not just to achieve a good working solution for the case study site, but also to test how combining drainage systems can result in a solution more effective than the sum of its parts.
The Judges liked this project for its brilliant use of technology to support design decisions. Billy thoroughly researched the background to the topic and presented his knowledge in a clear and understandable way. Judges were very complimentary about the approach to the work, his clear writing style, and his inciteful and to the point conclusions.
Billy demonstrates a deep knowledge and passion for the subject area, coupled with a strong determination to thoroughly explore the topic and draw meaningful conclusions. The work is aspirational in its conclusions, emphasising low-tech solutions in an industry that increasingly looks to technology to solve problems. The solution resulted in an exceptional retention rate to achieve greater sustainability for the case study site.