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Working with nature to reduce flooding

The recent spate of floods in the UK has intensified the discussion about how we prevent future flood damage. At times the debate has centred around traditional hard-engineering methods versus nature-based solutions, with the engineering proponents often highlighting the lack of evidence for alternative approaches.

The idea that conserving or restoring natural habitats and landscapes to alleviate floods is nothing new though. For example, in the middle of the 19th century, several European countries enshrined forest protection laws specifically to reduce the impact of future flood events. To paraphrase the early 20th century philosopher George Santayana, ‘those who cannot learn from history are doomed to repeat it’. So, are we finally beginning to appreciate what nature can do for us?

Well, perhaps we are, because the UK recently took a huge step forward to a renewed understanding of the role that natural flood management can have in protecting vulnerable communities.

Willow planted for bank stability (credit: Peter Leeson)
Willow planted for bank stability (credit: Peter Leeson)

Working with Natural Processes project

The Environment Agency recently published the outputs of its impressive Working with Natural Processes (WWNP) project which examines how we can use natural techniques to reduce floods and coastal erosion in urban and rural areas. WWNP brings together a huge amount of useful information into one easily accessible location and with just a few clicks you can quickly explore the full breadth of the work.

WWNP has created several useful products, all freely available online, including:

  • An extensive evidence directory
  • Guidelines on how to adopt natural flood management
  • 65 case studies of natural flood management from around the UK
  • Maps that identify potential areas to reconnect floodplains or to plant woodlands
  • A handy collection of one page summaries.

The evidence review crucially ascribes scientific confidence (low, medium or high) to the effectiveness of each process discussed, something that is particularly important with so much at stake. Another important part of the project is the discussion of the additional multiple benefits each process can provide, for example, planting floodplain woodlands can also improve water quality, create important habitats for wildlife and provide climate regulation.

Woodland stopping debris from going down stream (credit: Peter Leeson)
Woodland stopping debris from going down stream (credit: Peter Leeson)

The role of trees in reducing flooding

Of particular interest to us is the role of trees. Planting trees can help reduce flooding in two main ways: intercepting overland water flow by obstructing and physically slowing the rate of water running into rivers, and increasing the rate of water infiltration into the soil, which reduces the volume entering river systems.

WWNP delves deeper into how trees and woodlands can alleviate floods by also examining where they are effective. Three different types of woodland (floodplain, riparian and cross-slope) as well as larger-scale catchment woodlands (the total area of all woodlands in the landscape) are discussed. Each of these woodlands has a slightly different role in a landscape so it’s important to understand their strengths and weaknesses.

Importance of collaboration

There is one point to celebrate here that’s sometimes forgotten: this project brought together partners from several government, NGO and research organisations around the UK (including the Woodland Trust) and it is worth highlighting the benefits these collaborative approaches can have. The major environmental issues of today are more effectively confronted when we work in partnership with others to share data, experiences, skills and knowledge. But it’s not just research; much of the ongoing practical work the Woodland Trust does in this area would be immensely more difficult without the co-operation of other organisations, communities and individuals.  

Newlands Beck flooded  (credit: Peter Leeson)
Newlands Beck flooded (credit: Peter Leeson)

Informed decision making

The scientific approach the WWNP adopted is one of its great strengths, but the report highlights that natural flood management is not always the answer. There are gaps in our knowledge which the report spends a great deal of time discussing, so we should be fully cognisant of what natural processes can and can’t do. Natural flood management may be a cheaper and more effective solution in some circumstances; in others, hard engineering will be more appropriate. In many situations, both approaches will complement each other, often working together in several locations throughout a catchment. Understanding the limitations of each approach will enable us to provide a more effective flood alleviation scheme.

The trick for anyone concerned with planning flood alleviation schemes then is to take a wider catchment-based approach in order to maximise all available natural flood management opportunities. Some approaches may take time to be effective but it’s also worth remembering most of these approaches will provide multiple benefits too. In a country where competition for land use is so intense, this is perhaps the ultimate strength of working with natural processes.

Access the documents