Conservationists filled in 1.2km of a man-made river channel and allowed the water to spread naturally; the new Somerset wetland is now attracting rare wildlife

A new waterscape has been created on the Holnicote Estate in Somerset (National Trust photos)

Just one year after work completing a river restoration project in south-west England, researchers say the restored landscape has reduced flood peaks downstream, improved water quality and created new habitats for many species.The project took place on the National Trust’s Holnicote Estate in Somerset, where a 1.2-kilometre section of the River Aller was restored using a method called Stage 0 river restoration. The approach reconnects a river with its natural floodplain instead of keeping it confined to a straight, deep channel.Instead of flowing through a single managed channel, the river now spreads naturally across wetlands, ponds and multiple smaller channels.

The restoration has created around seven hectares of wetlands, covering an area larger than ten football pitches.The project was tested almost immediately after completion because England experienced its wettest 18-month period on record. According to researchers, the restored landscape handled the heavy rainfall well by storing more water on the site and slowing the amount flowing downstream.

Restoring natural flow

For many years, rivers across the UK were straightened, deepened and separated from their floodplains to improve drainage and support farming or development. While this helped move water away quickly, it also reduced wetlands and increased flood risks further downstream.Wetlands are among the most important habitats. They store water during heavy rain, release it slowly during dry periods, trap carbon and provide homes for many plants and animals. However, more than 90 per cent of the UK’s wetland habitats have disappeared over the past century, while more than 10 per cent of freshwater and wetland species are now threatened with extinction.The Holnicote project aimed to reverse some of these changes by allowing the river to behave more naturally again. National Trust Project Manager Ben Eardley said in the offician statement trying a new restoration technique was not without challenges.

“Trying any new technique is of course challenging but we need to be bold in order to tackle the climate and nature crisis.” He also said the difficult weather after restoration became an unexpected test of the project.“We had just the worst winter you can imagine post restoration in terms of the number of storms and sheer volume of rain. But despite it being record breaking conditions with high flowing water levels, the site responded really well, increasing the ability to store water within the site and lessening downstream storm flows, demonstrating the value of the restoration in providing resilience to hydrological extremes.“

A pond at Holnicote Estate, Somerset

Water and habitat changes

To understand how the restored landscape was performing, researchers from the Universities of Exeter, Nottingham, Loughborough and Umea University in Sweden monitored groundwater, river channels, water quality and habitats.One major finding was that groundwater levels increased sharply across the site. In some places, water levels rose by more than one metre. Dr Richard Mason from Umea University explained that this allows the floodplain to work like a sponge.“Ground water levels rose dramatically across the site, in some places by over a metre. This allows the site to act as a large sponge or filter in the river catchment, helping to store winter flood water, reducing flood risk downstream and releasing cleaner water more slowly in the drier months to help alleviate drought conditions.”As water now moves through vegetation, ponds and several channels instead of rushing through one straight channel, it also leaves behind more mud and sediment. Dr Mason said this natural filtering process helps improve water quality downstream.“The twists and turns and numerous flow paths that are now present in the floodplain as the water wends its way over the site through thick vegetation, act as a filter to capture sediment eroded from upstream.”He added that the restoration also created different water conditions needed by fish and other aquatic animals. “Put simply, the system has moved from a very tidy area with little for wildlife to a messy complex jumble of waterscapes and diverse habitats that is full to the brim with a huge variety of plants and animals,” he said.

Flood peaks fell, water cleared

Researchers from the University of Exeter used drones and sensors placed in the river to study how water moved through the restored landscape. Dr Alan Puttock and Professor Richard Brazier said the restoration reduced the speed at which floodwater travelled downstream.According to their monitoring, downstream flood peaks were on average 38 per cent lower after restoration. During storms, more water stayed within the floodplain instead of flowing rapidly downstream.The researchers also found that rainfall took longer to produce flood flows, giving the landscape more time to absorb water.They said the findings showed that allowing rivers to reconnect with floodplains could become an important nature-based approach for reducing flood risk.“These results mean that for the first time in the UK, we have seen the potential of allowing rivers to reset themselves to function naturally.”The monitoring also showed that average water turbidity, or cloudiness caused by suspended particles, fell by 41 per cent after restoration. This suggests that more sediment is now being trapped within the wetlands instead of being carried downstream.

A rare black-crowned night heron was spotted at Holnicote Estate (Representational photo)

Wetland habitat expands

Scientists also recorded a major increase in aquatic habitats. The total area of aquatic habitat increased from 0.18 hectares to 3.42 hectares, representing a 1,780 per cent rise.The restored landscape now includes slow-flowing wetlands, ponds, gravel beds and faster-flowing river sections. These different habitats support a wider range of wildlife and make the ecosystem more resilient.Dr Mason said even researchers were surprised by how quickly the site changed. “The speed with which the site developed into a diverse patchwork of habitats has been a real surprise.”He added, “What amazes me is the amount of wetland habitat created; the river has transformed from a pipe into a sponge.”According to Dr Mason, fish now have access to more space for feeding, shelter and movement, while young fish can use connected wetland habitats that have become rare across the UK.

Wildlife returns

National Trust ranger Jack Siviter said wildlife responded quickly after the restoration. “The site has gone bananas in terms of the amount of wildlife and lush vegetation growth that we’ve seen.”Large wetland plants such as Greater Tussock sedge have begun growing across the area. Thousands of wildflowers, including wild carrot, are also providing food for pollinating insects.The site now supports many water-dependent species including water voles, eels, trout, lamprey, grass snakes and waterfowl.Birds including swallows, swifts and sand martins have been feeding across the wetlands, while birds of prey such as red kites, buzzards, kestrels and sparrowhawks have also been using the area.Siviter said insect numbers have increased so much that large groups of swallows sometimes gather to feed.“One of the coolest species we’ve seen is a green sandpiper which is a great indicator species for healthy, lowland wetland habitat,” Siviter said.One species researchers are watching closely is the water vole. Before restoration, only limited signs of water voles were found along the edges of the site. New surveys by Derek Gow Consultancy have now found a dense population in the central wetland, with animals spreading across the restored habitat.In July 2026, the National Trust said a rare black-crowned night heron was spotted at the Holnicote Estate. The bird, considered a scarce visitor to the UK, was seen on estate cameras over three consecutive days, The Guardian reported.