Natural Flood Management (NFM) involves using landscape features and leaky woody dams to temporarily store water in times of heavy rainfall to reduce the brook levels and to slow the flow. Using the natural topography in wet corners of fields, low soil banks are constructed to temporarily hold back water. By encouraging water to spill into fields further upstream we can reduce the peak stream levels and settle out sediment and nutrients before returning the water to the brooks, improving water quality and keeping the soil and nutrients in the fields. This involves the cooperation of many partners, in particular landowners.

The Littlestock Brook, Bruern

NFM was trialled on the Littlestock Brook in the Evenlode catchment during a 5-year project (2016-2021) aiming to reduce flood risk to the small rural community of Milton-under-Wychwood, and enhance the river environment. The Environment Agency collaborated with Wild Oxfordshire, the Evenlode Catchment Partnership (ECP), Bruern Estate and the local community to deliver agricultural land management changes and NFM measures. This included constructing 15 field corner bunds (which temporarily store 30,000m³ of flood water), 27 leaky woody dams, planting 13 ha native broadleaved trees and de-culverting 100m of watercourse.

To reduce diffuse phosphate and sediment entering Littlestock Brook and improve wildlife habitats, the project also created 14 nutrient retention ponds and 1.1 km field margin sediment/nutrient traps, as well as planting 14.4 ha of riparian woodland and constructing a new footpath for recreation. The local community undertook tree planting and bank willow spiling in the parish field. Project interpretation boards will inform and educate visitors, encouraging them to engage by taking photos of the new ponds and landscape features to provide a visual record of their evolution.

The NFM project was selected as the winner of the Climate Resilient Places category in the Flood & Coast Excellence Awards 2021. Watch a summary video of the project below.

As one of the first NFM projects in the Thames basin, it increases our understanding of the effectiveness of working with natural processes for flood risk management in a lowland agricultural landscape. Hydraulic modelling results show that the new measures reduce the severity of flooding to 12 properties for a range of flood events.

A comprehensive monitoring network of water levels, sediment and nutrient fluxes in heavy-rainfall events has generated detailed evidence on the effectiveness of these features for flood risk and wider ecosystem services of water quality, habitat, and carbon. Critical to the project’s success has been integrated delivery through the ECP and local community to address multiple local environmental issues and to empower them to invest in their own catchment-based solutions. The power of positive landowner experiences will be key to widen the application of NFM to a scale which can make our catchments climate resilient places.

Bledington

The NFM scheme created in Bledington controls water flow downstream by holding up water flows upstream. This lowers the risk of flooding as the peak flow of water entering the river is lowered and delayed during rainfall events.

Six attenuation bunds have been installed in the first phases. In addition to intercepting surface water flows from the fields, water in the brook is forced out into swales during heavy rainfall events by leaky woody dams. This water runs down the field and is temporarily held back in storage areas, reducing peak flows downstream at Bledington where properties have been flooded in the past. The water is gradually released back into the brook over a period of one to two days.

Watch drone footage taken by Dave Gasca of retention bunds at Bledington below.