5 minute read
Littlestock Brook
Milton-under-Wychwood, Oxfordshire, United Kingdom
Reducing flood risk by using natural flood management measures. The village of Milton-under-Wychwood was flooded in 2007 during a flood event that affected large parts of southern England, with subsequent floods occurring in 2011. The Littlestock Brook project was initiated by the Environment Agency in 2016 after identifying the potential to reduce flood risk by deploying more natural flood management measures rather than using conventional “hard engineering.” To understand how a small, rural community could manage its flood risk, a partnership project was created with Wild Oxfordshire, Milton Parish Council, Bruern Estate, and West Oxfordshire District Council. The project was initiated and funded by the Environment Agency, which also oversaw its delivery. Wild Oxfordshire, as hosts of the Evenlode Catchment Partnership (ECP), managed the delivery of the project with support from HR Wallingford, UK Center for Ecology and Hydrology, Windrush AEC, and Whitehorse contractors. In a catchment upstream of the village, the Environment Agency and ECP developed natural flood management measures, including leaky dams, low earth bunds, tree planting, and sediment traps. Through detailed hydraulic modeling and extracting flood depths, it was possible to assess the effectiveness of the measures in reducing flood risk and undertake a cost-benefit analysis for the reduction in flood damages to properties affected by historic flooding. Phase 1 of the project was completed in 2019 and proved effective in December 2020 when the measures reduced flooding during a heavy rainfall event.
Article Cover: The Littlestock Brook as it flows through the Bruern Estate. (Photo by HR Wallingford)
Producing Efficiencies
The project was supported by a detailed 2D hydraulic model that identified areas where flows could be intercepted and measures implemented. It also demonstrated the efficacy of some existing measures and tested options for water retention and the design of outlet structures, with modeling for a range of rainfall extremes. The materials used in the low earth bunds were sourced from the site, minimizing transportation costs and disruption to the local community. The study revealed that optimal design of the low earth bunds in combination with leaky dams was critical, as significant water retention was required for flood risk reduction.
Using Natural Processes
The watercourses upstream of Milton-underWychwood have been modified over the years to increase agricultural production and allow for construction of a water mill. This has enlarged the channel unnaturally and “perched” it above the natural valley. The project has used natural processes to provide flood mitigation, including leaky dams to reduce the in-channel bankfull flow to a more natural one and allow more water to flow out onto the natural floodplains. The project also incorporated long-term land management with features like the planting of trees in the catchment intended to intercept rainfall and slow overland flows, thus reducing flood flows in the watercourses.
Broadening Benefits
The project is very much owned by the local community. The principal landowner, the Bruern Estate, was supportive from the outset, willing to donate land and effort. Community groups were involved with tree planting activities, and the ECP facilitated many project updates to the local residents. The project introduced nutrient retention ponds as well as field margin sediment and nutrient traps to limit diffuse phosphate and sediment in Littlestock Brook, planted around 14 hectares of riparian woodland to bolster wildlife habitat, and built a footpath to promote recreation. The newly created low earth bunds were planted with wildflower meadows, encouraging insect communities to thrive.
Promoting Collaboration
The project was initiated by the Environment Agency working with the local parish council and delivered in partnership with Wild Oxfordshire. Other key stakeholders included the West Oxfordshire District Council; Thames Regional Flood and Coastal Committee, who provided £230,000 of funding; and numerous research organizations interested in expanding the NFM evidence base. The community was actively involved and encouraged to document the new landscape features, and the project includes public access and information boards. The majority of the measures are located within the Bruern Estate, who worked with the project to develop solutions that met flood risk reduction, water quality, and habitat creation requirements without detriment to the estate’s agricultural work.
