The Environment Agency (EA) is trialling the Thames basin’s first natural flood management scheme, in conjunction with the Evenlode Catchment Partnership.
The five-year demonstration project was designed in 2016 and a report on the chosen measures was published in May.
The scheme will help meet Water Framework Directive (WFD) quality and habitat creation objectives, but its main aim is to determine whether multiple small-scale natural flood management measures can make a material difference to the extent and frequency of floods.
Work will be based around the river Evenlode, a headwater tributary in the Thames basin set in a flood-prone clay catchment.
The area has a legacy of land drainage and river channel straightening which means the channels have become too wide and deep, and disconnected from their floodplains.
The EA plans to reconnect the river with the floodplain and create four new wetlands. Other measures include water retention ponds, bunds and scrapes in grassland areas, leaky dams and woodland planting.
Action on water quality is needed too. In 2016, only one water body in the catchment achieved good ecological status, with ten failing for phosphate because of sewage effluent and diffuse rural pollution. Seven water bodies were deemed to have failing fish populations because of poor habitat.
In total, the project is estimated to cost £480,000 although this figure is likely to increase as it evolves. Some £200,000 will fund a catchment project officer and £280,000 will be spent on modelling, measures and monitoring.
The Thames regional flood and coastal committee local levy aims to raise £230,000 to meet the total over a five-year period. Another £150,000 will come from WFD grant-in-aid, £20,000 from flood and coastal risk management grant-in-aid, £5,000 from the parish council, £25,000 from the Cotswold Rivers Trust and £50,000 from local landowners.
The measures themselves are designed to be self-sustaining with minimal upkeep done via existing agricultural and environmental management. The maintenance and ownership of new structures will remain with the landowner but the partnership, which includes the parish council and landowners, says it will monitor the condition of the assets.
Despite good progress there remain a number of challenges. According to the partnership, the lack of “clear mechanisms to encourage farmers” to implement" natural flood management measures is one, alongside any penalties a landowner might incur by making land changes while they are taking part in an existing agri-environment scheme.
The report sets out further difficulties in demonstrating the benefits of such projects within the current flood and coastal risk management economic appraisal guidance and “negotiating and agreeing the ownership, liability and maintenance” of natural flood management interventions.
The “huge demand of time in building landowner and community partnerships” to deliver projects with integrated outcomes is also cited as problematic.
Results from the Evenlode project will be monitored and assessed by a number of organisations including the EA, the Centre for Ecology and Hydrology, Thames Water, the catchment partnership and the wider community.
The scheme is due to be completed in 2020.