5 minute read
Sidmouth amphitheatre
Jacobs-designed flood alleviation scheme which doubles up as an amphitheatre for the local community.
The Sidmouth flood alleviation scheme has seen the installation of a new drainage system to divert surface water away from properties. The water is guided via a swale to a flood storage area, which doubles up as an amphitheatre. The design enhances the local landscape and biodiversity – functioning as an outdoor performance venue and recreation space that can be enjoyed by the community, while ensuring it will remain unflooded in most rainfall events.
For many years, Sidmouth, a town on the south coast of England, has suffered regular stormwater flooding, with overland flowpaths draining to a low point directly in the town centre, putting up to around 150 residential properties and businesses at risk. If a rare, major storm were to take place, many local residential and commercial properties would be at risk of flooding.
Working with Devon County Council, Jacobs developed a flood management scheme that would overcome this and navigate the town’s drainage challenges – including a dense town centre, narrow streets and historic buildings with shallow foundations. Our team went further and were inspired to turn the flood defences into an amphitheatre, providing a public space for local communities to visit and use. We also reinstated a wildflower meadow and planted 11 new trees. Now over 300 people at any one time can enjoy local events in a unique natural setting, so long as the weather stays dry.
The project needed to consider how to intercept surface water flows on a busy highway and provide a flood storage solution to mitigate flood flows, while reducing flows into the town centre. More traditional approaches to mitigate flood risk were not viable with the town’s narrow streets and historic buildings, so the storage scheme needed to be located further upstream in an area of open parkland, which was acceptable to the local community and sensitive to the impact on the mature trees. Favouring Sustainable Drainage Systems (SuDS), we focused on creating an environmentally friendly solution using Innovyze drainage design software, diversifying the flora and supporting the needs of nature, while creating a useful asset for the community. We developed a landscape vision for the storage area, with an amphitheatre as the focal point of the scheme, creating a venue for community and festival events.
With a strong focus on using recycled, upcycled and sustainable materials wherever possible, we developed a broader system design comprising two 'crossdrains', which take water off the highway and towards the parkland area, with the outfall discharging into a swale. This leads to the flood storage area –the amphitheatre – designed for dual use. In normal weather conditions the storage area is a stunning outdoor amphitheatre for general amenity use, festivals and other town events. During extreme rainfall events, water intercepted from the highway will flow along the swale and infiltrate through the surface of the amphitheatre into a sub-surface geocellular crate system. Once the sub-surface storage is full, water will pond on the surface of the amphitheatre. Water can leave the amphitheatre through a combination of the infiltration system and a piped outflow to the nearby surface water/sewer network at a greatly reduced rate. In the event of a blockage of the outlet, a spillway can direct flows safely overland into the adjacent area of the parkland.
Using this blue-green infrastructure solution helps improve the water quality of the runoff, as it filters through grass and stone media. We incorporated several innovative features and designs, including a carefully developed step design to the tiered seating with state-of-theart, plastic-free grass product and reinforced earth techniques to resist erosion. A lockable, self-raising cover and frame was developed to protect the central flow control chamber from any movement and make for easy-access maintenance.
The dual-use approach used here is a model for how all projects should be conceived wherever possible. Flood defences should benefit the community all year round as opposed to simply when there is a flood event. Maximising the use of blue-green infrastructure in our public realm will provide wildlife habitats, local amenities, and mitigate some of the effects of our changing climate. Our green spaces are enormously valuable to local communities, providing mental health benefits, cleaning the air and water, and reducing the urban heat island effect for those living in our cities and urban spaces.
This culturally relevant solution integrates the vital stormwater management into a creative, environmentally sensitive, climate-resilient design – enhancing the local landscape and biodiversity, while functioning as a delightful performance venue and community recreation space, now being fully enjoyed by all.
Paul Hargreaves, Jacobs Senior Associate Director, developed the overall SuDS design concept, coordinated the diverse and holistic design team, and supervised during construction.
Andy Craven-Webb, Jacobs Associate Director, led the landscape design and assessment work on the project from planning through to site supervision.
This culturally-relevant solution integrates the vital stormwater management into a creative, environmentally sensitive, climate-resilient design – enhancing the local landscape and biodiversity, while functioning as a delightful performance venue and community recreation space, now being fully enjoyed by all.
