Reintroducing wiggles to river systems

Rivers naturally meander through their valleys as the water seeks the line of least resistance. These bends, twists and turns mean the river channel is long and winding; it can hold more water, there is variety of depth and speed of flow which provides varied habitats for a wide range of plants and animals. The flood plains on either side of a meandering river offer a natural reservoir for excess water when heavy rain produces too much for the river channel to hold, soaking into the soil, absorbed by wet-loving vegetation and trees. The wet meadows hold water until levels decrease and the river returns to flow in its usual channel, slowly fed from the saturated environment around it.

This creates a once highly valued environment, enriched by periodically deposited silts, creating seasonal grazing for livestock, and year round variety of habitats that ensure the health of the river and its landscape. The mixture of fast and slower flowing water provides areas where fish can rest and spawn, promotes good water quality and enables a wide range of creatures and plants to flourish.

In the past focus was more on maximizing the use of wet land for increasingly intensive agriculture. Methods of land drainage, including straightening rivers, were introduced, with the intention of moving water downstream fast. This had the effect of detaching many rivers from their natural flood control mechanisms – the flood plains. As fertile flood plains have been increasingly used for crops, or in more recent years for development, the need to protect them from flooding has become paramount. What is now being realized by many organizations is that the artificial means of controlling flooding – ever higher flood defences, dredging to deepen channels and promote a faster flow to move water downstream – cannot control water levels effectively.

With the erratic and often extreme rainfall related to climate change, trying to move water downstream faster often results in more serious flooding downstream. As well as the flood risks, straightening and deepening river channels can also have a devastating impact on biodiversity; creatures need the variety of habitats provided by bends and wiggles in river courses, and by the seasonally wet land of water meadows.

Our little River Tas is one of only 200 chalk streams in the world - a rare resource. It is one of those rivers which used to meander across its valley and was then straightened, most recently in the 1940s. We may call it ‘little’ and over the last summer it has certainly seemed very tame and unthreatening. The reality, we know, can be very different. The extremely wet weather in December 2020 saw the river become a raging torrent with severe flooding affecting several houses nearby. Since then there has been much discussion about how to stop this happening again. 

Ordinance Survey maps showing past and present course of the River Tas. Environment Agency 

Information from The Environment Agency (EA) in August outlined their plans developed with landowners, Norfolk Rivers and Natural England to reintroduce meanders to a stretch of the River Tas where it flows through the SSSI behind St Peter’s church.

The EA evaluation is that the straightening work shortened the channel, pushed the river closer to housing and deposited the spoil from the new channel on the downhill side of the river. This effectively cut the river off from the lower lying part of its flood plain and means in times of heavy rain it is more liable to flood towards nearby housing until it reaches a level where it can overtop the spoil. The plan is to lower the downhill bank (east side of the river) and reinstate three previous meanders, lengthening the channel by 240m. We should see the work for this start this Autumn.

These Natural Flood Management techniques are expected to provide more effective use of the floodplain away from properties, as well as improving the environment for wildlife and biodiversity. Organizations throughout Britain and Europe are using the rewiggling of rivers to manage flood risks. Hopefully it will prove to be successful on the Tas.

If you have questions about the work on the River Tas please contact the Environment Agency by emailing:

References

Environment Agency Newsletter Forncett St Peter Floodplain re-connection scheme https://forncett.info/activities/forncett-nature-matters/forncett-nature-notes/861-river-tas-floodplain-reconnection-scheme.html

Websites

Thames 21: The importance of wiggles in a river system

The Flood Hub: How restoring rivers natural curves can prevent flooding.

CIWEM: What the river wants.

The National Trust: Riverlands: how we keep our rivers flowing

October 2025