Aylesbury Sustainable Drainage Systems (SuDS) Retrofit

Location: Aylesbury                                                                 Client: Buckinghamshire Council


Aylesbury holds Garden Town status, and this is viewed as an opportunity to create a greener, more resilient and more successful town for current and future residents. The town centre is currently dominated by grey impermeable spaces. Buckinghamshire Council identified 12 locations within Aylesbury town centre (including streets, squares, car parks and public open spaces) where there may be opportunities to create multi-functional spaces through the retrofitting of blue-green infrastructure including Sustainable Drainage Systems (SuDS). This project aimed to investigate the feasibility of implementing SuDS in these locations, considering opportunities and constraints including: effectiveness at delivering multiple benefits and compliance with the Aylesbury Garden Town principles; buildability; stakeholder perceptions and public acceptability; land ownership; comparative costings and timescales. 


We held two stakeholder workshops with representatives from Buckinghamshire Council (Flood Risk and SuDS, Planning, Conservation, Environmental Health, Trees, Parks, Landscape), Transport for Buckinghamshire, Aylesbury Garden Town, Aylesbury Town Council, Aylesbury Town Centre Manager, and Thames Water Utilities Ltd. Stakeholders identified the top three benefits as: creating attractive urban spaces, resilience to climate change and reducing storm runoff. Concerns were raised around long-term maintenance, below ground assets, access for public uses of squares (markets and events) and anti-social behaviour.

We undertook a site visit and desk study for each area, examining ground conditions, services records, trees, ecology, flood risk and drainage, land ownership, infrastructure, transport and parking, conservation area status. A long-list of the potential retrofit interventions was compiled for each site, including consideration of site-specific opportunities and constraints.

The long list options were assessed in collaboration with Buckinghamshire Council, preferred combinations of blue-green interventions were chosen for each area, and concept designs and simple visualisations were developed.

Aylesbury SuDS Retrofit Visualisation

Two methods were used within the study to assess the benefits of the short-listed interventions. A multi-criteria analysis, which captures both constraints and benefits qualitatively, and a monetary assessment of benefits using the CIRIA Benefits Estimation Tool. However, it was still difficult to fully value all the benefits. For example, in Aylesbury urban placemaking and footfall in retail streets is arguably more important than flood risk as a key driver, but it is not possible to reliably quantify the direct impact of blue-green interventions on the town centre economy.

High level costing of the schemes was carried out, broken down by proposed components, so that the final choice of options can be based on available budget.


The project demonstrated that retrofitting SuDS in Aylesbury town centre would meet many of the Garden Town aims and has the potential to deliver cost-beneficial schemes with multiple benefits. The application of an integrated holistic approach, incorporating SuDS retrofit interventions in the design of other Garden Town and town centre regeneration initiatives, rather than focusing on a single benefit such as flood risk will help to ensure that cost-benefit of such schemes is viable in terms of both construction and future maintenance costs. Where such initiatives are being developed, the information, visualisations and conceptual designs produced by this study will enable early engagement on the potential for SuDS in Aylesbury. The study has also highlighted short-term quick wins which could be used to showcase the benefits of these types of measures.

Want to know more?

Email Anna Beasley for more information on this project, and on Blue-green infrastructure and SuDS.

You can also find out more about these services on our Local Flood Risk Management web pages.

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