4 minute read
Belford Natural Flood Management Scheme
Belford, Northumberland, England, United Kingdom
The Belford Burn is a small stream that runs through the center of Belford Village against private garden boundaries and walls. Belford village flooded 10 times between 1997 and 2007, with a history of flood events dating back to 1877. The six-square-kilometer catchment is predominantly in rural areas upstream of the village. Traditional flood defenses were not suitable due to high costs, lack of space for infrastructure, and low population. After the flood in 2007, the Environment Agency of England (EA) delivered an alternative catchment-based solution to the problem and commissioned Newcastle University to monitor the catchment, conduct hydraulic modelling, design run-off attenuation features (RAFs), engage with landowners and the community, and appoint specialist contractors to deliver the interventions. Since construction began in 2008, 45 RAFs have been constructed (amounting to 12,000 cubic meters of storage) and only one property has been impacted by flooding. This project resulted in the concept of Catchment Runoff Management Plans, which manage flow pathways directly by storing, slowing, and filtering farmland runoff. The features are multipurpose and address water quality trap sediment, create new habitats, and store and attenuate flood flow. This project was awarded the Robert Stephenson Award from the North East branch of the Institution of Civil Engineers in 2012 for using small features instead of traditional infrastructure for flood protection.
Article cover: Runoff attenuation—leaky dam installed to capture surface flows. (Photo by Alexander Nicholson, Newcastle University)
Producing Efficiencies
Catchment monitoring of rainfall, river level, and river flow began in winter 2007, and the first four RAFs were constructed in September 2008. Once the RAFs were constructed, water level sensors were installed in each of these RAFs to monitor response during storm events. The monitoring network expanded in 2009 with the addition of two more temporary river level gauges, a permanent EA flow gauge, and an EA rain gauge. Monitoring of individual RAFs has shown that they are able to have a significant impact (up to 10 percent reduction) on the flood peak in small-to-medium events.
Using Natural Processes
The EA funded the application of an upland catchment management program with the support of the North East Regional Flood and Coastal Committee. This followed early evidence gathered as part of a research project at Nafferton Farm, where corner-of-field ponds and ditch management were used to mitigate high flows. The approach presented in the proactive study was to install passive intervention on farms to control large volumes of runoff. Belford’s upland catchment management program began in September 2008 and has involved the construction of approximately 45 individual mitigation elements using natural processes in the form of small storage features, ditch management, large woody debris, and soil berms installed across fast runoff pathways. These features offer not only flood protection but additional benefits not provided by traditional flood-protection structures.
Broadening Benefits
The features are multipurpose and address water quality, trapping sediment, creating new habitats, and storing and attenuating flood flow. New woodland planting in the riparian area replaced sycamore trees, which were felled to create the large woody debris dams, with lower-growing native tree species. The trees do not have large canopies and allow more light to enter the woodland, which enables a greater amount of vegetation to develop on the woodland floor. Apart from helping to create greater floodplain roughness during periods of sudden flood, the vegetation provides a richer habitat to small mammals and birds. Habitat for the great crested newt, a European protected species, was restored in one online RAF in particular.
Promoting Collaboration
This project was a partnership between the EA, North East Regional Flood and Coastal Committee, Newcastle University, and local landowners. A PhD study funded by the Engineering and Physical Sciences Research Council through the Flood Risk Management Research Consortium and the EA was initiated to monitor and develop hydraulic tools to measure and simulate the impact of Natural Flood Management (NFM) in the Belford catchment. From a landowner and community engagement perspective, the project has been profoundly successful.
