4 minute read
Marlfield Farm
Earby, Lancashire, United Kingdom
Applying a pilot flood risk management technique on a smaller farm scale. Situated in the foothills of the Pennines, the City of Leeds, United Kingdom, is predicted to be impacted significantly by ongoing climate change between 2039 and 2069. To offset these impacts, a natural flood management (NFM) project was piloted to provide climate resilience using nature-based solutions. Marlfield Farm, in the catchment of the River Aire upstream of Leeds, was identified as a suitable pilot site to test and trial the implementation of NFM on a traditional upland family farm. It enabled the project team to learn lessons and facilitated upscaling of NFM delivery to hundreds of sites across the 700-square-kilometer River Aire catchment. The Environment Agency led the project on behalf of the Leeds City Council, who worked together with the Procter family (the farm owners), Mott MacDonald (the designers), and the River Stewardship Company (the contractors). The objective was to deliver a range of NFM measures to slow the flow of rainwater before it enters a local tributary of the River Aire and to improve habitat for local wildlife. Works have included creating wetlands, forming seasonal habitat ponds using earth bunds to hold surface-water runoff, planting hedges and trees, installing a leaky barrier, and fencing off field corners from grazing to promote vegetation growth. The project was completed in 2019.
Article Cover: The pilot natural flood management (NFM) project was completed at Marlfield Farm in Lancashire in 2019 to help protect the Aire catchment from flooding. (Photo by Mott MacDonald)
Producing Efficiencies
The Marlfield Farm pilot site was used to understand how the Environment Agency, which normally delivers large flood alleviation schemes, could approach NFM on a smaller farm scale, providing operational efficiencies while maintaining a robust procedure to manage environmental, health, and safety risks. Design drawings were produced using a modular approach; a single standard design could be used for multiple NFM features across the site, saving on cost and time. Hydrological analysis was undertaken to estimate the predicted flood risk benefits from the NFM on Marlfield Farm, which helped inform wider hydraulic modeling and monitoring strategies for the whole Leeds NFM project.
Using Natural Processes
The project team consulted with the farmer, whose family has worked the site for generations, to form a plan to enhance natural processes and reconnect fragmented habitats. Features were positioned to intercept overland flows across the site’s main drainage routes and direct runoff to storage features. Marl (clay) was sourced on site to build an earth bund. Existing boundary drystone wall material was repurposed to form a leaky barrier, with a strengthened wall fitted with high-level overflow pipes passing excess flows to other NFM features. Within the woodland where runoff occurred, locally sourced hazel was used to make a woven leaky barrier.
Broadening Benefits
Along with other pilot sites on the Leeds NFM project, Marlfield Farm has been used to show stakeholders and the community a practical example of NFM. The farm owners have led group tours of the site, including an NFM community group in 2022, where they discussed how well the NFM works had established during the three-year period since installation. The team used local contractors during construction wherever possible, reinvesting the project funds into the local economy. Since construction, the farm owners have observed the performance of the NFM works during storm events and noted a range of wildlife using the new habitats.
Promoting Collaboration
Work on the Marlfield Farm pilot site was concurrent with Mott MacDonald leading a partnership for the Construction Industry Research and Information Association Natural Flood Management (CIRIA NFM) Manual. This work collated a wide range of research and engagement to bring together NFM best practices. The CIRIA NFM Manual delivery process was applied to project development; working with others was central, and project initiation started with understanding the catchment. Measures were selected in discussion with the landowners and designed and constructed by the project team. Future monitoring and maintenance of the features will be undertaken by the landowner.
