This blog been written by a member of the Newground Flood Team.
With towns and cities home to the majority of the UK’s population, demand on drainage systems has increased significantly over the years. Traditional hard engineering schemes, such as improvements to culverts, highway drainage, and sewers, have their place in managing flood risk. However, upgrading these systems is expensive, disruptive, and increasingly unsustainable. With the number of homes at risk of flooding expected to double to around 10 million within the next 30 years, it is critical that we explore alternative approaches to reduce pressure on traditional drainage infrastructure.
When the term natural flood management is mentioned, it often conjures images of rural landscapes: in-stream structures like woody dams, woodland creation, land management techniques and floodplain restoration or storage in upper catchments. But can these principles be applied within towns and cities? And if so, what does urban NFM look like in practice?
A major point of debate around NFM is the definition itself. The word “natural” can be interpreted in multiple ways. Does it refer only to the use of natural materials and features, or does it emphasise managing water through natural processes?
Some experts argue that soft engineering techniques, such as earth bunds or woody dams, qualify as NFM because they use natural materials. Others disagree, noting that constructed features are not fully “natural” when compared to river and floodplain restoration or the reintroduction of native vegetation. Similarly, Sustainable Drainage Systems (SuDS) are sometimes considered a form of urban NFM, but opinions vary.
Perhaps the focus should be less on the materials used and more on the processes. If water is managed in a way that mimics natural systems, slowing runoff, improving infiltration, increasing retention, then it arguably aligns with the principles of natural flood management, whether in a rural or urban setting.
When the term natural flood management (NFM) is used in conversation, consideration will nearly always lean towards more rural based works in the upper catchment involving the likes of in-stream structures such as woody dams, woodland creation, land management techniques as well as floodplain restoration and storage options. But does natural flood management fit the urban landscape? And, if so, what does it look like?
The natural flood management definition and the context in which it is used leads to much debate about what actually classes for, or technically qualifies as NFM. In breaking the term down, it appears to be the ‘natural’ element which causes the most confusion. Does it relate to the use of ‘natural’ materials and features alone, or does it in fact lay more emphasis on water being managed through ‘natural’ processes?
For example, some say that soft engineering is within the remit of natural flood management, because earth bunds or woody dams are using natural materials. Others disagree, because any form of ‘constructed’ engineering is not reflective of the landscape in its natural state, as would be achieved with river and floodplain restoration or the reintroduction of sphagnum moss to the moorlands. Similarly, some consider Sustainable Drainage Systems (SuDS) to be a form of NFM, while others do not. So, does the answer lie more in the destination rather than the journey, the end result? Regardless of whether the objective is achieved through soft engineering or through SuDS, if the water is managed through natural processes, then should it not qualify as natural flood management? After all, it makes allowances for landscape features, whether rural or urban, to be used, restored and more importantly altered to process water in a ‘natural’ way.
In which case, many (but not all) SuDS would technically be natural flood management measures. Not only do they have the same ideologies of controlling and processing water at source, improving infiltration to the land, increasing attenuation, retention and controlling conveyance, but many of them deal with water through natural processes and with natural materials. It is also worth noting that both up-stream, rural based NFM works and urban SuDS also share many other similarities and benefits; in particular biodiversity and conservation, improving water quality, reducing carbon and other pollutants, building resilient ecosystems, improving green spaces and building on community spirit!
For instance, many would not consider a green roof to be a natural flood management tool as it uses some non-natural materials, such as for the insulation layers and waterproof membranes. In reality though, a green roof uses natural materials such as soil, sand, grass, plants and flowers to manage water naturally through the process of infiltration, transpiration and evaporation. The green roof is effectively adapting the urban landscape to restore what would otherwise be the natural foot print of the land if the built environment was not in situ.
Many Sustainable Drainage Systems (SuDS) can be considered urban NFM measures. SuDS share the same core objectives as traditional NFM: controlling water at source, increasing infiltration, managing conveyance and attenuating surface water. They also bring additional benefits, such as enhancing biodiversity, improving water quality, reducing carbon, creating resilient ecosystems, and supporting community wellbeing.
Take green roofs, for example. While they incorporate some non-natural materials, like insulation layers and waterproof membranes, they also use soil, plants and natural processes such as infiltration, transpiration and evaporation to manage water. By effectively reintroducing a “natural footprint” into the urban landscape, green roofs reduce runoff, ease pressure on drainage systems and contribute to urban cooling and biodiversity.
Other urban NFM techniques include:
Historically, urban landscapes and buildings have been designed with little adaptability for natural flood management. Most NFM measures seen today were integrated at the design stage of new developments. However, recent planning policies, increased focus on sustainability and innovation in urban design are changing this.
Modern building developments are increasingly incorporating SuDS and other green infrastructure solutions, while retrofitting existing urban areas is becoming more common. Swales, retention basins, permeable pavements, and urban wetlands are now being used to collect, store and infiltrate water naturally, reducing reliance on traditional drainage systems and helping to replenish groundwater, which accounts for around 30% of the UK’s water supply.
Examples of urban NFM in action can be found across the UK. Sheffield city centre, which has experienced multiple devastating floods, is exploring the use of public parks as temporary flood storage areas following community consultations. Similarly, rain gardens, green roofs, and infiltration basins are being implemented in cities like Manchester, London, and Birmingham as part of urban regeneration projects.
Whether or not you consider SuDS to be a form of urban natural flood management, the principles, objectives and benefits are strikingly similar. By combining traditional flood infrastructure with NFM and SuDS approaches, towns and cities can become more resilient to flood events.
Integrating natural flood management into urban planning is not just a complementary solution, it is increasingly a necessity. Future cities must prioritise sustainable and natural approaches to manage the growing flood risk, protect communities, and enhance biodiversity, green spaces and overall environmental quality.
Utilising a variety of natural and sustainable flood alleviation solutions ensures towns and cities are better prepared for the floods of tomorrow. The integration of NFM and SuDS will play a critical role in creating resilient urban environments that support both people and nature.
To learn more about the different methods of sustainable drainage systems, download our SuDS Booklet here.
