RSA Insurance, an Intact company, and The Wildlife Trusts commissioned Stantec to write Assessing the multiple benefits of Natural Flood Management. 

*Natural flood management includes: 

• Planting trees, hedgerows, woodland: to capture rainwater before it hits the ground, slow overland flow, and increase water storage below ground 

• Bringing back beavers: their activities store water in the landscape through building dams, digging channels and more 

• Creating ponds and wetlands: to collect water, and hold it in wet periods  

• Restoring peat bogs: which can hold vast amounts of water  

• Regenerating soils and wilder grasslands: improving soil structure allows rainfall to penetrate the surface, and rough, tussocky grasslands are more effective at storing water than intensively managed grasslands  

• Constructing leaky dams or log diverters: to release water slowly and to move waters out onto flood plains rather than build up in a river  

• Restoring rivers: re-engineering or modifying a river’s course to restore its natural meandering shape or to improve its ecological health mitigates high flow events  

• Sustainable Drainage Schemes: measures to increase water infiltration in urban areas such as de-paving, ponds or vegetated ditches (bio-swales) 

Evidence collated by Environment Agency: Working with natural processes to reduce flood risk 2024 - GOV.UK  

For more information about the case studies examined in the report see: 

• The Sherbourne Valley Project | Warwickshire Wildlife Trust 

• Limb Brook: Nature-based Solutions Demonstrator - Sheffield & Rotherham Wildlife Trust 

• River Otter Beaver Trial | Devon Wildlife Trust 

• Gloucester and Cheltenham Waterscapes | Gloucestershire Wildlife Trust 

Stantec  

The research was undertaken by Stantec – a global leader in sustainable engineering, architecture, and environmental consulting. The project involved the review of a number of Wildlife Trusts projects, using limited data to examine a range of additional environmental and social benefits from natural flood management schemes beyond mitigating the impacts of flooding. 

Natural Flood Management funding 

Public funding for NFM remains a small proportion of overall flood risk mitigation. The largest current public fund in England is the Environment Agency’s £25m Natural Flood Management Programme, which is less than 1% of the total flood and coastal erosion risk management budget for the next 12-month period. Whilst a blended financial approach to NFM can be highly successful in meeting project objectives (especially for multiple beneficiaries for flood risk mitigation, or multiple benefits), current private investment in NFM is very limited. A number of barriers / challenges exist for investors engaging with NFM projects, including a lack of certainty in any market. Unless these are removed, and confidence is increased, perhaps through increased public funding, private investment will remain limited. 

Leaky dams and retention ponds, Upper Sherbourne, Warwickshire  

Leaky dams are made from wood (logs or trees) that are cut into short, manageable lengths and placed at right angles across a ditch or stream. They are held in place to secure them. The wood is stacked just above the natural water level so that during normal conditions the water continues to flow underneath. In high level rainfall events the water level in the ditch or stream rises and the water gets caught behind the wood. As there are tiny gaps between the wood that is stacked, the water leaks through. Hence a leaky dam as the structure slows the flow without completely preventing it. Hundreds of leaky dams are installed on ditches and streams across a landscape and the cumulative effects of slowing the flow of water result in a reduction in the 'peak flow' of the river downstream. The peak flow is the top height the water level reaches and reducing the peak flow even by a couple of centimetres can be the difference between flooding that causes damage or not. 

The Natural Flood Management project involves working with landowners to identify the right solution in the right place. Sometimes the better option (or as an additional feature) is to create a retention pool. Retention pools are shallow bowls cut into the soil in key locations that act as water storage areas during high rainfall events. The rain lands on the grounds and either flows over the top or through the soils and a retention pool can intercept it as it moves downhill. Retention pools are created using diggers to scrape out the soil in a field. The soil scraped out is often put on the low side of the retention pool to create an additional lip (increasing the height and the volume of the feature and allowing it to hold more water). Retention pools drain slowly over time, releasing the water after the main extreme weather has passed and helping to reduce the peak flow further downstream. In dry spells the retention pool can become vegetated and blend into the landscape, not being obvious at all. They 'activate' when high rainfall events occur. These features can be incorporated into grass fields where livestock graze and the farmer can continue to manage the land in the way they did before. 

The Wildlife Trusts 

The Wildlife Trusts are making the world wilder and helping to ensure that nature is part of everyone’s lives. We are a grassroots movement of 46 charities with more than 910,000 members and 39,000 volunteers. No matter where you are in Britain, there is a Wildlife Trust inspiring people and saving, protecting and standing up for the natural world. With the support of our members, we care for and restore over 2,600 special places for nature on land and run marine conservation projects and collect vital data on the state of our seas. Every Wildlife Trust works within its local community to inspire people to create a wilder future – from advising thousands of landowners on how to manage their land to benefit wildlife, to connecting hundreds of thousands of school children with nature every year.

RSA Insurance, an Intact company 

RSA Insurance is a multinational insurance group. We are one of the world’s oldest general insurers. We provide peace of mind to individuals and protect small businesses and large organisations from uncertainty. We use our capabilities to anticipate and improve outcomes for customers by our direct channel, our broker relationships or partner organisations. We have established businesses in the UK, Ireland and continental Europe. In 2021, the former RSA Group Plc came under new ownership and is now a wholly owned subsidiary of Intact Financial Corporation (IFC). IFC has invested heavily in building resilient communities since its inception in 2009, funding over a hundred climate resilience projects from coast-to-coast in Canada.