Why we need to talk about floodplains
This post is by Stewart Clarke, national specialist of freshwater, catchments & estuaries at the National Trust.
Whether it’s floods or drought, water is on the frontline of the climate crisis. This summer’s huge floods in Germany and Belgium, followed days later by those in central China once again prompted debate about managing floods and development in the floodplain. Whilst everyone seems to acknowledge the folly of building on floodplains, it still seems to happen, and we cannot avoid the fact that we already have lots of homes and infrastructure in these high risk places. So, while we must stop this type of development, we must also think carefully about how we use the remaining undeveloped parts of floodplain. In short, we need to think about floodplains in the UK differently.
It’s time for a rethink
We tend to think of floodplains as land that gets flooded when things go wrong but we need to revise our collective understanding because, by doing so, we will manage them very differently.
Most river scientists would recognise the description of the river channel as the ‘dry’ weather channel and the floodplain as the ‘wet’ weather channel. By recognising the floodplain as the space for water during wetter times of year it suddenly doesn’t make sense to use them for anything that might be vulnerable to flooding. Indeed, it then follows that we should ensure they are prioritised to withstand what is likely to become more and more frequent flooding.
Happily, there are plenty of benefits for people that can happily co-exist alongside making space for water.
Most floodplains aren’t fit for purpose
Research shows that over 90 per cent of UK floodplains are ‘not fit for purpose’, occupied as they are, by urban development, arable farming and improved grassland. As well as being liable to flooding, these modified floodplains shift water much faster downstream creating flood issues for communities. By repurposing them to help us deal with the consequences of the climate and nature crises, we can both secure huge benefits for people and wildlife and avoid some of the costs associated with inappropriate use.
Properly recognised, our floodplains could deliver a big chunk of the government’s ambitions around nature, climate and public engagement with nature.
Imagine a broad network of green corridors snaking through our countryside, linking existing natural habitats and reaching into our cities and towns. This is what alternative use of floodplains could deliver. Such a vision is the epitome of the proposed Nature Recovery Network for England and, planned right, it could also help reduce flood risk, store and lock up carbon and create space for people to enjoy nature, all on top of the obvious benefits for nature. If we displace some of the most intensive land use, we can even begin to improve the quality of the rivers themselves.
The National Trust is changing its river landscapes
At the National Trust we have been exploring ways in which land by the river can help to create more nature rich habitats, space for water and tackle climate change. Increasingly, it is this land that floods that prompts conversations about how to adapt to an uncertain future.
As well as changing land use, work will often be needed to ensure water gets onto the floodplain as levels rise and can flow back into the channel as levels fall. This ‘hydrological connectivity’ is critical to the workings of rivers and is the thing we have lost through decades of unsympathetic river management.
In our restoration projects under our Riverlands programme we have removed embankments to allow rivers to reconnect. Frequently, years of channel dredging have left the channel much lower than the floodplain and so, as we are doing on the Scarrow Beck in the Bure in Norfolk, it is also necessary to bring in material to build up the riverbed to reconnect the ‘dry’ and ‘wet’ weather channels.
At Goldrill Beck in the Lake District we are moving the river from its former straightened course into a newly created meander loop; water flowing through this new course is slower and there is more habitat for wildlife in the new channel but, importantly, the levels will allow the floodplain to store water once again.
At Holnicote on Exmoor we’ve gone one stage further and trialled a new technique, pioneered in the US, of full floodplain reconnection (aka Stage Zero restoration), in which the over deepened channel and historic drainage has been filled in. The result of this reconnecting water with the floodplain is many small shallow channels which spread water slowly across a rich wetland environment.
Such dramatic changes are not possible everywhere and floodplains are still some of our most productive land, so it makes sense to look for farming systems that can work with functioning floodplains. Our ancestors knew this well and, once, lowland floodplains were the most valuable farmland of all, delivering a rich hay crop and excellent grazing, fed by nutrient rich floodwater. These ancient floodplain meadows are just one of the habitats we are restoring along the Culm at Killerton in Devon with the support of a Defra Green Recovery grant. We are now working with the Floodplain Meadows Partnership to identify further opportunities across our land to restore this unique habitat.
In short, we have a growing list of projects, but this work has only just begun. With 1.6 million hectares of floodplain in England and Wales, there is plenty of room for this sort of restoration. Our floodplains have room for trees to soak up carbon and slow floodwaters, wildflower rich meadows that can work with modern farming systems and complex wetlands, where reed, scrub and open water ebb and flow with floods and grazing pressure. And there is room for beavers too, should we decide to bring these ecosystem engineers back in force.
Three actions needed
With a fundamental review of how we support farming and new agricultural schemes on the horizon, new flood risk management strategies in England and, finally, political acknowledgement of the urgency around climate change, it’s time to rethink how we use our floodplains. Here are three ways to start:
1. Define floodplains and give them special status
A simple map of floodplains linked to planning, agricultural, biodiversity and water management policies would help to make the right decisions about how we use this critical land. By explicitly recognising floodplains in new agricultural schemes, we could target and encourage restoration of floodplain function.
2. Set new targets for restoration
New targets for nature and habitat restoration should recognise the huge contribution floodplains can make to people, nature and climate. Restoration of the rich mosaic of habitats that characterise natural floodplains could make a significant contribution to overall UK nature recovery.
3. Introduce ways to drive floodplain recovery
The government’s recently launched England Woodland Creation Offer acknowledges the importance of trees and woods in riparian corridors and could help expand the extent of floodplain woodland with the wide range of ecological and societal benefits this could bring. The challenge now is to provide similar incentives for other floodplain habitats across the UK