Urban Green DaMS (Design and Modelling of SuDS)

Lead Research Organisation: Newcastle University
Department Name: Sch of Engineering

Abstract

If we don't manage rainfall appropriately, it can lead to flooding. Traditionally, urban areas have been drained using underground sewer systems. These can be expensive and disruptive to build and maintain. Storm runoff collects contaminants as it flows over urban surfaces and through sewer pipes, and is a significant cause of river pollution. In many cities, combined sewers discharge raw sewage into natural water bodies during storm events. Without intervention, growing populations and the effects of climate change will increase the frequency and severity of urban flooding and pollution events.
As an alternative to building more/larger sewers, we are starting to implement SuDS (Sustainable Drainage Systems). SuDS is an overarching term for a 'toolbox' of techniques that aim to deal with the quantity of rainfall, but also to have a positive impact on water quality, amenity and biodiversity. Retrofitting SuDS into urban areas can help to improve stormwater management within our existing urban areas. Vegetated bioretention cells (often referred to as rain gardens) are one of the simplest, practical and most reproducible SuDS options. They can be fitted adjacent to urban streets, dealing directly with road runoff.
Bioretention cells are emerging as a preferred option in the USA and Australia. However, we do not yet have the same understanding of their performance as for traditional measures such as pipes. This is because they have 'living' elements (i.e. plants & soil) whose functionality varies from place to place and over time. The soil has a critical role to play in supporting plant life and managing runoff. Bioretention cells typically use engineered soils or 'substrates' that need to meet specific physical requirements. To reduce the requirements for imported materials, we need to be confident of their performance with locally-sourced substrate components, thereby reducing cost and improving overall sustainability.
Water usage by plants helps to reduce runoff. We will observe plant water usage (evapotranspiration rates) in six full-scale bioretention cells functioning under semi-controlled conditions as part of the Newcastle University's new National Green Infrastructure Facility (funded by UKCRIC: EP/R010102/1). Controlled tests using smaller columns at the University of Sheffield's climate controlled laboratories will allow us to explore more substrate options. We will measure plant respiration in installed SuDS systems to generate a database of evapotranspiration rates for different urban plant types.
Bioretention cells slow down excess flow before it is passed to the sewer. We will carry out a detailed investigation of how the substrate and drainage outlet arrangements affect runoff detention. Information relating to maintenance needs is particularly sparse, with clogging of substrates especially poorly understood. We will use magnetic, fluorescent, tracer particles to explore the vulnerability of substrates to clogging by the dirt and fine particles present in road runoff.
Drainage engineers use hydraulic models to represent catchment runoff and sewer system flows. The new data will allow us to develop a numerical model of bioretention cell rainfall-runoff processes. Our project partners include the developers of the most widely-used drainage network modelling tools. We will work with them to include bioretention cells in their software. We will also update the cutting-edge urban flood risk model CityCAT to incorporate bioretention cells.
Soil and vegetation conditions change over time in response to seasonal weather patterns, and vegetation lifecycles. Furthermore, the hydrological response is sensitive to rainfall duration and intensity, as well as antecedent soil moisture conditions. Conventional approaches to sizing drainage components tend to ignore all these sources of variability. We will develop new SuDS design guidance that uses probabilistic performance functions to address this.

Publications

10 25 50
 
Description Expert Advisory Board Meeting April 2019 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Approx. 8 non-project attendees, from among our Project Partner group (https://ugdams.sites.sheffield.ac.uk/project-partners). As this was the first EAB meeting, the focus was to explain our project objectives, and to allow our Partners to comment and/or share their ideas and experience.
Year(s) Of Engagement Activity 2019
URL https://ugdams.sites.sheffield.ac.uk/outputs-publications
 
Description Expert Advisory Board Meeting September 2019 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Approx 6 non-academic attendees, from among our Project Partner group (https://ugdams.sites.sheffield.ac.uk/project-partners). As this was the second EAB meeting, the focus was to discuss progress to date, and to allow our Partners to comment and/or share their ideas and experience.
Year(s) Of Engagement Activity 2019
URL https://ugdams.sites.sheffield.ac.uk/
 
Description H7O: Global Water Security Innovations and Challenges 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Organised a major international symposium on water security. Led to follow on interactions with industry and national and international researchers.
Year(s) Of Engagement Activity 2020
 
Description International Expert Advisory Board Meeting July 2019 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact This was a meeting with our International Academic Expert Advisory Board. Exchange of information on recent and current research relevant to the project, particularly from Australia, New Zealand, USA and France.
Year(s) Of Engagement Activity 2019
 
Description Sky News - 6pm National News, 18th Feb 2020 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Interviewed about floods and climate change impacts.
Year(s) Of Engagement Activity 2020
 
Description WaterAid Summity 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Supporters
Results and Impact WaterAid Water and Climate Summit. Participation in the session on Climate Change Adaptation.
Year(s) Of Engagement Activity 2020
URL https://www.wateraid.org/uk/media/hrh-the-prince-of-wales-and-wateraid-to-host-major-water-and-clima...