The Natural Flood Management Approach
Natural flood management can be described as:
“a suite of techniques that aim to work with natural, hydrological and morphological processes to manage the sources and pathways of flood waters. At the same time natural flood management can improve the quality of our natural and urban environments and provide many additional benefits for water quality, ecology, climate change, and recreation” (Scottish Environment Protection Agency, 2012).
A large range of NFM techniques exist. Evidence varies about the likely impact of each technique. For the majority of techniques the certainty with which the impact can be predicted is low and the impact is likely to vary with location conditions (soil, slope, land use intensity etc). Some examples are given below:
- Conifer and broadleaf woodland planting: There is consensus that the effects of forestation diminish with both catchment size and event magnitude, but the location within catchment is significant;
- Reducing grazing pressure on pasture: This technique aims to improve soil condition and water infiltration. Research shows that there may be a reduction of 13% or more in run off;
- Creation / restoration of non-floodplain wetlands: It is often thought that wetlands act as a sponge, but this is not borne out by the evidence. Research provides conflicting messages about the effect of wetlands on reducing flooding. Each wetland is unique and effects can be both positive and negative;
- Blocking Upland drains: There is general agreement in the literature that upland drains can lower moisture conditions but could also improve connectivity to watercourses;
- Floodplain reconnection: This can increase the travel time of water through the catchment and there is general consensus that it reduces flows, but there is disagreement on the magnitude of the impact;
- Creation of constructed farm wetlands or ponds: These features increase storage in the catchment. Research shows they require careful design and may still have uncertain impacts depending on local conditions;
- Improved management of lochs and reservoirs: The literature shows that changing the management of lochs and reservoirs can reduce flood flows.
- Reach restoration: This can help in moving water past receptors, and the research shows that local effects can be significant, with a low degree of uncertainty.
- Use of SUDS (sustainable urban drainage systems): Research shows that well designed and maintained systems are known to be effective with a low degree of uncertainty.
For more information contact: Wendy Kenyon