How can woodlands help reduce flood risk?
Pickering, in North Yorkshire, has a long history of flooding. More recently, floods occurred in 1999, 2000, 2002, and most notably, in 2007, when 85 properties were flooded, causing an estimated £7 million of damage.
Because Pickering Beck flows through a steep sided valley for much of its length, the town is particularly vulnerable to ‘flash flooding’. Some parts of the town have a 10-25% chance of flooding in any given year and the aim of the project was to try and reduce this to a 4% chance or less. Could this be achieved by implementing a range of land management and soft engineering measures?
In 2009, Defra set up a flood management demonstration project in Pickering called ‘Slowing the Flow’, one of 3 pilot projects established following the 2007 Pitt Review into the floods in England. Its aim was to work with nature, storing more water in the landscape and slowing its passage downstream. The partnership project is ongoing (2009-2015) and led by Forest Research, closely supported by Forestry Commission England, the Environment Agency, The North York Moors National Park Authority, Natural England, Durham University, Local Authorities and the local community.
A number of the land management measures being demonstrated involve the targeted use of woodland to help slow the flow, including planting some 42 ha of riparian and farm woodland, constructing 175 ‘large woody debris dams’ in river tributaries, and restoring streamside buffer areas within forest plantations. Other measures include blocking moorland drains, constructing timber ‘minibunds’, establishing ‘no-burn buffer zones and improving soil conditions on farmland to reduce rapid runoff.
The main soft engineering measure involves the construction of a large flood storage ‘bund’ at Newtondale, upstream of Pickering. This should be completed later in 2014 and is designed to hold back some 120,000 cubic metres of floodwater at times of peak flow in Pickering Beck.
Whilst the implemented measures will not prevent all floods, they should reduce the risk of Pickering flooding in any given year to a 4% chance or less. The measures will also deliver a wider range of benefits, including carbon sequestration, habitat creation, reduced diffuse pollution, and training and education. Economic analysis of the woodland measures alone shows a positive Net Present Value (based on 2013 prices) ranging from £0.1-1.9m for the Pickering Beck catchment, with a central estimate of £0.9m. This suggests that from a societal perspective the public benefits outweigh the costs, although the opposite would be the case for private landowners.
The priority is to complete the construction of the flood storage bund by the end of 2014 to secure the improved level of flood protection for Pickering. Thereafter, efforts will focus on extending the land management measures to further reduce the risk of flooding. Monitoring and evaluation will continue to build the evidence base.Add Pingback