Innovation Project SLD2316
Restoring Floodplain Woodland for Flood Alleviation
Aim
To facilitate the establishment of a significant area (~15 ha) of floodplain woodland in the River Laver catchment to demonstrate and help communicate the benefits of this option for flood alleviation.
Project Description
The Government’s Flood and Coastal Erosion Risk Management Strategy, Making Space for Water, promotes a whole-catchment approach to flood alleviation, drawing on opportunities provided by rural land use and land management practices. Woodland provides a number of options, principal amongst which is the ability of floodplain woodland to slow down flood flows and enhance flood storage. Research work suggests that the greater hydraulic roughness provided by floodplain woodland could make a significant contribution to downstream flood alleviation.
There are increasing opportunities for planting and extending relic areas of floodplain woodland to help reduce downstream flooding, but progress is highly constrained by a lack of information on the magnitude of the forest effect and how this is affected by woodland design and management factors. While most of these issues can be investigated by modelling work, a robust assessment requires a demonstration study.
The existing Multi-objective, Defra/Environment Agency/English Nature/Forestry Commission Pilot Project on the River Laver in North Yorkshire provides an ideal opportunity to establish a demonstration floodplain woodland. Four potential sites have been identified for planting and local landowners are supportive, in principle. However, planting has not been possible due to insufficient financial support to cover the costs involved with this change in land use.
The aim of this project is to facilitate the establishment of a demonstration floodplain woodland at one or more of the identified sites as a novel approach to flood risk management. This will be achieved by the following objectives:
| 1. | Evaluating the impact of planting floodplain woodland on flood flows and flood risk at Ripon. |
| Hydraulic models will be applied to the River Laver and available stream flow and high resolution topographic data used to assess the effect of planting floodplain woodland at each of the four potential sites on flood flows. The results will be assessed in terms of flood risk at Ripon and the sites ranked by their effectiveness at alleviating flooding. | |
| 2. | Investigating the influence of woodland design and management factors on flood flows. |
| The same models will be used in an innovative way to evaluate the effect of varying the design and management of the woodland on flood velocity, depth, storage volume and peak travel time. Factors to be considered include the shape, area, pattern and spacing of tree planting, species choice, woodland structure and establishment methods. The findings will guide the design and management of the planned woodland at the preferred site(s). | |
| 3. | Facilitating an application for Woodland Creation Grant under the English Woodland Grant Scheme. |
| The appropriate landowner(s) will be assisted in making an application to the Forestry Commission for grant aid to establish a floodplain woodland at the preferred site(s). The results of the modelling work will be used to supplement the standard scoring system and support the application for funding. Top-up funding will be provided by the project to cover the full cost of establishing the woodland and better reflect the potential flood alleviation and other benefits. Planting floodplain woodland will provide additional benefits for society and the environment, including improvements to water quality, fisheries, carbon sequestration, nature conservation, recreation, and landscape. | |
| 4. | Assess the impact of planting floodplain woodland on flood depth, velocity, storage and timing. |
| Additional instrumentation will be installed at the selected site(s) to measure the initial effects of the site preparation and planting of the floodplain woodland on flood flows. Monitoring will be maintained by the Forestry Commission beyond the three-year duration of the project to evaluate the longer-term effects on floodplain roughness and flood flows as the woodland becomes fully established and matures. The results will be used to validate and improve existing models, enabling them to be applied with confidence at other UK sites. | |
| 5. | Demonstrate and communicate the benefits of floodplain woodland for flood alleviation. |
The findings from the project will be disseminated via a Forestry Commission Forest Practice Note, Forest Research website and by amendments to the Woodland Creation Grant, Regional Forestry Frameworks, and the Forests & Water Guidelines. Group visits to the demonstration woodland and outreach seminars will help to communicate and explain the benefits of floodplain woodland for flood retention to practitioners, planners and policy informers. The main outcome from the project will be a demonstration of whether floodplain woodland can make a significant contribution to reducing flood risk. A positive result will strengthen the evidence base and support for using floodplain woodland as a sustainable method for downstream flood alleviation. It could also provide significant socio-economic benefits by helping to tackle the increasing threat of flooding faced by many local communities due to climate change, especially where it is not cost effective to construct engineered defences. There is also an opportunity to develop win-win solutions due to the ability of floodplain woodland to benefit water quality and freshwater habitats, which would contribute to meeting ecological and chemical quality targets under the EU Water Framework Directive. Finally, the proposal will help to meet the UK Biodiversity Action Plan Target of creating 2,200 ha of wet woodland in England by 2010. The results, models and guidance derived from the project will support better integration of woodland and agriculture for flood alleviation elsewhere in the UK, as well as in the identification and prioritisation of sites for future action. |
Project Duration
3 years
Project Leader
Dr Thomas Nisbet, Forest Research
Page last modified: 10 January 2007
Page published: 4 January 2007