Appropriately located and designed new woodland can help reduce flood risk and/or diffuse water pollution. The ability of trees to deliver water benefits depends on the location of the new woodland as follows:
- Wider catchment woodland - planting here can help reduce fertiliser and pesticide usage; protect sensitive soils from disturbance and erosion; increase infiltration and reduce water runoff; and intercept sediment and chemical pollutants in run-off, reducing the delivery of pollutants to watercourses.
- Riparian woodland - planting along watercourses can create a buffer between rivers and the adjacent land, intercepting and removing nutrient pollutants and sediment in run-off; providing a barrier to pesticide spray drift; protecting river banks from disturbance and erosion; slowing flood flows; and providing shade to reduce thermal stress to fish and other aquatic life.
- Floodplain woodland - planting here can act as a partial barrier to a river when in flood. This helps to slow flood flows and encourages the deposition of sediment and the retention of pollutants on the floodplain.
- Cross-slope woodland – planting of smaller areas (typically belts) of woodland (all types) across hill slopes. Cross-slope woodlands can intercept pollutants and reduce rapid runoff from higher land. They can also encourage infiltration and increase the soil’s water storage capacity.
In some circumstances, woodland creation can have a negative impact on water resources and/or water quality. In some parts of England, the high water use of conifers and short rotation energy crops can threaten local water supplies and river flows, while the ability of woodland canopies to ‘scavenge’ acid pollutants from the atmosphere can exacerbate surface water acidification. In others reduced river flows can be detrimental to water-dependent protected sites.
Where the scale and type of woodland planting suggests these might be an issue, you should seek advice from available data published online, the Environment Agency, local water company and/or Natural England and use the advice received to inform the woodland creation proposal.