River Restoration Archives - South East Rivers Trust

What’s in a river? We’re using eDNA to find out

Posted on 8 April 202424 April 2024 by Ian Lamont

Dr Lewis Campbell, one of our Catchment Managers, reports how we have introduced a modern method of assessing what’s in rivers to our armoury.

Traditionally, a variety of methods have been used to evaluate biodiversity and to understand whether or not a specific species is in a particular place in the countryside. When it comes to fish, for example, these survey methods might involve the use of nets or electrofishing equipment. For mammals, methods can involve field surveys looking for footprints, droppings, burrows and dens, or installing hidden cameras that are automatically triggered with movement. When studying birds, ecologists might spend time in the field searching for visual signs or identifying different species by their calls.

Trout — Our work seeks to help trout recolonise the Hogsmill. Picture via Canva

For smaller creatures, such as amphibians, reptiles and even invertebrates, various types of traps can be deployed so that the animals can be collected and counted before being released again.

One thing that this diverse set of methods all have in common is that they require a large amount of time to be spent on site. More recently, conservationists have begun to use environmental DNA, or eDNA for short, as a tool to understand species distribution. As animals go about their daily lives, they are continually shedding cells into their environment. These cells might come from their hair, skin, saliva, or even their waste, but they all contain the genetic material (DNA) belonging to that animal within their nucleus. This is environmental DNA.

Rivers could be compared to a soup containing cells and DNA from all of the organisms that live in or near by the water.

Simply by collecting a water sample, we can gain a snapshot of all the animals that were in the local vicinity at the time. We pass river water through an extremely fine grade filter, then generate and analyse the genetic sequences that the sample contains. A single water filter sample can reveal the presence of hundreds of different species from right across the animal kingdom.

eDNA is quite a modern technique. The first example to detect species in a freshwater environment was in 2008, when French researchers used the technology to detect invasive American bullfrog. Since then, technology and its potential applications have improved and expanded rapidly.

Preparing to take a sample to find out the DNA of the Hogsmill

The analysis portion of this work requires numerous pieces of cutting edge technology and very powerful computers, but collecting a water filter sample is very straightforward and quick. This means that it is possible to comprehensively survey the biodiversity at a location much more efficiently than is possible using many traditional methods.

The only major drawback of eDNA surveys is that they can currently only provide information on whether a species was or was not in a given location but not how many were there. For example, using eDNA you could say “I did detect salmon in my river” but not “there were 50 salmon in my river”.

This means that it is a particularly powerful first pass tool for determining presence or absence of a species, which would then by followed up with more targeted traditional surveys. Therefore, eDNA will never replace the valuable work of professional ecologists, but is certainly a very important emerging tool in the conservationist’s arsenal.

At the South East Rivers Trust we are beginning to use eDNA to understand the biodiversity in our rivers before, during, and after our restoration work. This is critical to developing an understanding of whether or not the projects that we undertake are having the desired positive outcomes for the wildlife that call our rivers home.

An important example of this type of baselining is our WET Hogsmill. This is funded by Natural England and aims to kick start the recovery of several species of concern in the River Hogsmill in South West London.

These species – water vole, European eel, and brown and sea trout – are imperiled across our river network, but all of them historically called the Hogsmill home.

Our WET Hogsmill project will enhance the river to make it more accessible and more useable for these species, aiding their recolonisation of the river. Environmental DNA is a great tool for us to demonstrate where these species are living along the river. The aim is that over time this will document increases in the numbers of places where specific species are found along the river.

So far we have undertaken a baseline eDNA survey at several points along the Hogsmill, from near its source, to its confluence with the Thames at Kingston. We collected water samples that were used to detect a wide variety of vertebrate species. We found mammals including red fox, grey squirrels, and wood mice. We detected fish including barbel, chubb, stickleback, and many others. We also found birds including the majestic kingfisher, grey heron, magpie, moorhen, coots, and parakeets.

Importantly, we also detected the presence of eel, water vole and brown trout at locations on the Hogsmill, so we know those species are present and we hope that our work will help them to become better established on the river.

The initial survey’s results can be found on our Storymap and we will continue to monitor the river with annual eDNA surveys – so watch this space!

Glorious gravel boosts the Blackwater

Posted on 21 March 202426 March 2024 by Ian Lamont

Assistant Project Officer Luke Beckett reports on a week-long series of events with volunteers in mid-March, putting gravel into a stretch of a River Loddon tributary to improve conditions for river wildlife.

River Blackwater gravel installation — Some of the gravel was transported by dinghy © South East Rivers Trust

Anglers and conservation enthusiasts were among more than a dozen volunteers who joined us for the exhausting but rewarding task of installing more than 19 tonnes of gravel into the River Blackwater. In joining us earlier this month, they added a vital resource to help nature thrive into a 200 metre stretch of the river in Aldershot.

The newly seeded gravel, which is the final part of our Blackwater Valley river restoration work, will provide improved habitat for macroinvertebrates such as beetles, dragonflies and mayflies. It will also help aquatic plants thrive, as well as increasing spawning habitat for fish.

The River Blackwater at Ivy Road has historically suffered from bank and riverbed modifications. This section of the River Loddon catchment has been widened and deepened, leaving a uniform channel with little variation in water depth.

The channel has lacked flow energy and habitat diversity and subsequently, silt and fine sediments had built up, smothering the riverbed. Moreover, the site is just downstream of the Aldershot sewage treatment plant, which regularly discharges sewage effluent into the channel.

Since 2021, the South East Rivers Trust has worked with support from the Environment Agency and the Blackwater Valley Countryside Partnership, plus local volunteers, to improve this stretch of river.

Installing gravel at River Blackwater — Will the pile of gravel ever go down? © South East Rivers Trust

The in-channel deflectors and berms previously installed have helped to narrow the channel and increase water flow velocity, as well as habitat complexity. The increased velocity has already cleared much of the fine sediments and silt.

The newly-seeded land-based gravel will move around with the natural ebb and flow of the river, settling to form natural river features, such as bars, riffles and deeper pools.

This clean gravel and variety of river habitats is essential for river life: the River Blackwater supports a number of fish species – such as chubb, roach, perch, dace, gudgeon and rudd – all of which should benefit from this improved spawning habitat.

Gravel seeding is not the most glamorous of tasks. This site delivery was no different and was made difficult by the lack of access routes.

Raking gravel into the River Blackwater © South East Rivers Trust

Large vehicle access to the river was not possible, which meant a lot of moving wheelbarrows loaded with heavy gravel from our drop off location to the channel itself.

The distance was at least 75 metres and up to 200 metres to push the gravel to the correct places, making this tough physical work. Wader wearing volunteers also had to rake the gravel once in the riverbed, sometimes having taken it to an appropriate location in a dinghy.

It was slow going at times, leaving us questioning whether the gravel pile was even going down! But, after four days, including a lot of rain, not enough sunshine and many teas, coffees and biscuits, the gravel pile was finally gone and the last wheelbarrow and boat load were emptied.

The team took a moment to look over their hard work from Ivy Bridge, where a few curious fish were already checking out the new riverbed, before the heavens opened once again!

This brings our river restoration work at Ivy Road Recreational Ground to a close, but we look forward to returning over the coming months and years to see how the channel responds.

Gravel and brash berms — The final scene: Gravel on the left is complimented by previously installed brash berms on the right © South East Rivers Trust

4 reasons to start your career in restoring rivers

Posted on 19 December 202319 December 2023 by Polly

“There is nothing better and more rewarding than seeing wildlife spring back to life on a river, especially when you have been involved in all aspects of the project, from conception through to design, delivery and monitoring. Seeing the direct impact you have had for the environment – makes this a very special job.” Toby Hull, Head of Restoring Rivers and Catchments

We’re currently recruiting to our Restoring Rivers and Catchments Team. It can be hard to picture yourself in a new role from just a job description, so we have curated the top reasons to start your career with us and help bring rivers back to life.

1. Job satisfaction and pride in your work

“If you love the outdoors and rivers, and are concerned by the issues facing them, working for SERT will help you achieve a real sense of job satisfaction. Being able to scope new projects, obtain funding, develop and design the project and then go out deliver the physical works is hugely satisfying and rewarding – and rare to be able to do all of that.” Harry Clark, Project Officer.

In many jobs, it can sometimes be difficult to see the direct impact your work has had. But at SERT you can see this in spades. Working as a Project Officer, or Senior Project Officer, you manage projects from conception to completion. You help identify what needs to happen, develop, and design the works, obtain permissions and funding, and then physically make the change on the ground. There is no greater sense of pride than seeing a stretch of river come back to life thanks to a project you designed and delivered.

“It’s an extremely friendly working environment with open-minded people. There is such a wide range of expertise across colleagues and that makes for great learning opportunities.” Caroline Ritchie, Project Officer.

2. A varied and unique role

Project Officer, Caroline, securing baffles to facilitate fish passage.

Working in the RRC Team is like no other career. There is a huge variety and scope in the type of projects you might be working on any given week. We break out concrete to naturalise riverbeds and banks. We create and enhance habitat by introducing wood and gravel back into rivers. We remove river barriers such as old concrete weirs to open up fish migration routes and to let rivers flow freely once again. We build wetlands and install ‘end of pipe’ solutions to improve water quality. We install leaky woody structures and build sustainable urban drainage solutions (SuDS) to help reduce flood risk. We love making meaningful and physical changes to the environment.

So what does a typical week look like for one of our Restoration Officers? You might start the week with the RRC Team meeting to catch up with colleagues on projects and a project meeting with external partners such as the local water company, Environment Agency or local council. On Tuesday, you’d head out to the river for a walkover with a local landowner, identifying opportunities to restore a stretch of river. Wednesday you could be installing large woody material in a chalk stream with an enthusiastic and friendly group of volunteers. Perhaps on Thursday you’re designing a wetland to clean up pollution before it enters a chalk stream. Finally, Friday you might pull together a proposal for a project, finalising the outline design and sending it off to a prospective funder.

As SERT works across the South East of England, our RRC Team have projects to improve rivers in a variety of different places and habitats ranging from working in highly urbanised sections of river, to public parks, through to small villages and across private farmland where you can really embrace the peace and quiet, working to improve wetlands, backwaters and chalk streams.

“We have a brilliant team with a wealth of experience and expertise in the river restoration sector.” Luke Beckett, Assistant Project Officer.

3. A wide range of training and a whole career pathway

Brasted Lower Weir being removed — The RRC Team tackle breaking up a weir.

Joining the RRC Team at SERT, you are provided with formal training, in-house experts and projects to build your skills and experience, which combined helps you to progress your career at SERT.

Practical training for countryside management often includes outdoor first aid, brushcutting, chainsaw, and basic tree felling certificates. Desk-based training has covered wetland design, CDM, contract writing, site safety and softer skills such as funding and project management. And not to mention river surveying techniques such as River Morph, Sniffer assessments for fish passage and Redd surveys. As an organisation, SERT’s action is led by sound scientific understanding and best practice. Projects at SERT span across multiple teams, you get to learn on the job from the years of experience in the RRC Team, as well as the varied skills and knowledge from the other teams at SERT.

If the knowledge from just SERT isn’t enough, we are part of The Rivers Trust movement – a network of 65 other rivers trust across England, Wales and all Ireland – the fastest growing environmental movement of today. We network at conferences, as partner on projects and share best practice in our day to day work to ensure we are all learning as one.

Our Project Officer, Harry Clark, joined the Trust as an Assistant Project Officer. Since then he has worked on a range of projects and been trained in many aspects from the use of chainsaws to underground cable avoidance. Harry spent time out in the field installing natural flood management measures, supported large-scale restoration work for our Acacia Hall River Restoration and was then supported in developing and leading his own projects. He’s learnt a wide range of skills and developed a sound understanding of managing rivers and their catchment while working with us which has led to his promotion.

We are one of the largest trusts and offer good career progression through a variety of roles within our trust. Or if you wanted to move to a different region, your skills would be directly transferable to another rivers trust so you’re in safe hands with us.

“It is rewarding and fulfilling. To work alongside passionate, genuinely interested individuals who, like you, are in it for the love of the job, environment and reward it offers.” Luke Beckett, Assistant Project Officer.

4. We’re a fun and friendly team

The RRC Team posing for the Acacia Hall Restoration Project.

We know everyone says we’re a fun and friendly team, but we really are. We’re all in our roles because we care about the environment and want to make positive change. We’re passionate, supportive, creative and our core driver is that we make the right difference for nature.

A bonus? We love our puns!. So don’t hold bass, there is no trout about it – read our job adverts and if you’re interested in these eely fintastic roles (which we think you will be) let minnow.

Check out our vacancies now!

Could you help us this Giving Tuesday?

Posted on 31 October 202327 November 2023 by Ian Lamont

Think of us on #GivingTuesday – 28th November

Giving Tuesday was created in 2012 and has now grown into an international movement that is embedded on the social calendar annually, with the simple idea of doing good.

What better way is there to do that than make a donation on Giving Tuesday (28^th November 2023) or instead of a physical present this festive season, to help protect rivers – our very lifeblood?

While there are many great causes, one that underpins our very existence – water – is hard to ignore.

Much of our drinking water is abstracted from rivers, supplementing what is stored in reservoirs to supply the needs of our homes and businesses.

However, in the South East we live in an area that is classed as water-stressed. This means that we are already facing a water shortage because of a growing population and climate change, which brings with it erratic weather patterns, from sudden storms from which we can’t capture all the water to drought.

All this puts huge pressure on the wildlife that thrives in rivers. Your rivers. Rivers that have been straightened, boxed in by concrete or boarding along the edges thwarting animal movement between water and land, or restricted by weirs and other barriers – all in the name of convenience for people at various times in our history.

But this has left our rivers unable to function as they should, to allow fish to migrate (some as far as the sea) to better habitats, to allow flowers to flourish to attract pollinators, or to give creatures that move between water and land the chance to do so.

The very habitats that support the wildlife that supports our existence needs help – and we’re on a mission to make that happen.

However, we can’t install fish passes or ‘rewiggle’ rivers to make them places where aquatic life can truly thrive without funding.

By the end of November, many people are already making decisions about gifts for the festive season. Many of you might be tempted by offers on Black Friday weekend (23^rd to 27^th November). But many of you might be thinking that a gift to nature might be better for your recipients for Christmas-time festivities this year – a year in which we have made inroads in many areas.

Some highlights from this year include:

encouraging people in the Medway to take a first step to caring for their local river by addressing their reliance on single-use plastic – 70 people signed up to become official Medway River Guardians with many of them becoming River Champions.
working with landowners in the Beult to install nature-based solutions to retain back water in the landscape for the benefit of wildlife and people. We’re now building up similar work on the Darent
creating new fish passes, from a baffle weir to improving the wish stream so fish can access better habitats
training citizen scientists to map out invasive non-native species on the Wandle and continued our volunteering events at Morden Hall Park
starting to create a new wetland at Chamber Mead on the Hogsmill
introducing rivers to dozens of schools and hundreds of children through our education programmes
Hosting Loddon Rivers Week and contributing sessions to London Rivers Week
Setting up a project to reintroduce water voles, eels and trout to the Hogsmill
Advising the UK’s largest greenhouse salad crop grower on water resilience

We couldn’t do it without funding.

Please consider making a one off donation to the South East Rivers Trust this Giving Tuesday, or signing up to make a regular donation. Visit our donate page for details.

A backwater to boost the Teise

Posted on 30 October 20237 March 2024 by Ian Lamont

Anglers have already reported seeing small fish using a new backwater on the River Teise in Kent just days after it was created by the South East Rivers Trust.

Taking just over a week to construct in September, the backwater has created a refuge for aquatic life taking cover from high flows or pollution incidents emanating from the main river.

A natural depression had formed in the landscape

A natural depression in the landscape, which might actually have been the original course of the river, proved the perfect place to construct this new backwater, near Goudhurst.

The depression was dug out to a size of 20×8 metres by our contractors FGS Pilcher. They used two diggers and four dumpers to create the full depth of the wetland.

The deepest section was created where it would be fed by the river and then a slope was built to the far end. This will prevent fish becoming trapped and ensure that the backwater will always hold water, even during low flow conditions.

It is always a bonus when materials can be reused. We placed root plates and large pieces of timber within the backwater to provide additional habitat. The complex root plates provide great cover for juvenile fish, while the large pieces of timber may be used by amphibians accessing or exiting the backwater, or as a perch for birds.

We also have plans for other large pieces of timber generated during the construction works. We will be returning to the site to introduce some of these big bits of wood into the river, to help increase habitat diversity within the Teise itself.

We have recently planted some of the backwater edges with ferns and other flora sourced from the riverbank nearby. These have been supplemented with a natural pond/wetland seed mix to attract insects and birds when they grow next spring. These will help the backwater become a haven for dragonflies and damselflies.

The work, supported by the Environment Agency, is part of our mission in the Teise Habitat Improvement project to improve this sub-catchment of the River Medway.

In recent years we have removed four concrete weirs to allow fish to reach different habitats and added woody materials such as deflectors to improve river habitat.

We have also worked closely with the Teise Angling and Conversation Society to improve the course of a heavily modified and dredged river and improve the habitats for brown trout, rainbow trout and grayling which frequent the watercourse.

Working wonders in Wandle Fortnight

Posted on 28 September 20232 October 2023 by Ian Lamont

Dozens of volunteers made a huge difference to the River Wandle during Wandle Fortnight (11^th-24^th September), carrying out restoration or learning to record invasive species across the catchment.

Firstly, about 40 volunteers in total worked across five days at Morden Hall Park, continuing our on-going work along this section of the Wandle at the National Trust site.

In a separate event, we also trained more than 20 people how to spot invasive non-native species (INNS) so they could go out during the Fortnight and record their presence using an App, to inform our catchment work.

These two events were intrinsically linked: when we take volunteers to continue our Morden Hall Park work twice a year in autumn and spring, the first task is to remove floating pennywort. This invasive plant is regularly seen across other parts of the Wandle and was one of the top types of INNS our volunteers were trained to record.

We also took the opportunity of Wandle Fortnight to schedule an event to talk to residents about a weir lowering project.

The problems with pennywort

Removing floating pennywort at Morden Hall Park in September 2023 as part of Wandle Fortnight

Like many invasive species, the pennywort might look colourful, but this fast-growing plant crowds out native plants, takes oxygen from fish and insects and cuts out light, inhibiting aquatic wildlife. At Morden Hall, the removed pennywort is composted by the National Trust. It can form a big mat, meaning volunteers drag this a short distance to a boat or suitable exit place for it to be lifted out of the water.

If pennywort is left to decay in the river, the bottom of slow moving sections as useful river channel for wildlife, depleting oxygen levels as it breaks down. This further serves to prevent many invertebrates and other species from completing their life cycles, reducing biodiversity.

Once we removed the pennywort, volunteers then turned their efforts to installing four more deflectors – large pieces of wood – and creating three more berms along the banks at Morden Hall, completing the current round of work, funded by the Environment Agency, we have been doing there since 2020.

Watch volunteers work on a berm

Manoeuvring the deflectors and putting stakes in to keep them in place is tough physical work, but the benefits are huge as we change a once-straight river into a meandering channel where the flow is much more varied. These large tree chunks, cut down as part of woodlands management by the National Trust, help to clean gravels and create pools behind them, providing areas where fish can spawn and thrive.

Planting a berm at Morden Hall Park on the River Wandle — Volunteers planting a berm at Morden Hall Park on the River Wandle

The berms, which are built as an extension of the sides of the river, are made of brash. Volunteers planted them with sedge species that work best in shady areas. These plants were mostly relocated from the wetlands and help to filter out pollutants and excess nutrients while providing habitats for invertebrates. Golden flag iris was one plant inserted into these berms. Volunteers, many of whom have returned after previous sessions, could see the vegetation from previous efforts providing nourishment for nature.

Project officer Harry Clarke said: “The twice-yearly efforts by volunteers at Morden Hall Park are really starting to bear fruit and be visible. Now we can see moor hens, herons and ducks regularly making the most of the benefits of a narrower river channel and much more vegetation along the banks.”

The flow of the river now has a much more meandering course as a result of our work over the past few years – and our video shows the results.

Training volunteers to help us map invasive plants

Our INNS training session at Sutton Ecology Centre was attended by 22 people, who learned about various plant species that do harm to our rivers. Newly educated, they were empowered to carry out surveys on walks alongside rivers, starting in Wandle Fortnight. They have until the end of October to record them on an . The data these citizen scientists collect will help us – as catchment partnership hosts for the Wandle – form plans to tackle INNS on the entire river network in the future.

While floating pennywort, Giant Hogsweed and Himalayan Balsam might be best known and the most common invasive fauna on our rivers, volunteers were also trained to look out for Japanese knotweed, parrots feather, New Zealand pygmy weed and giant rhubarb.

Japanese knotweed, introduced to the UK in the mid-1800s, is known to be along the river at Poulter’s Park. Emerging in March, it can grow at 5-10cm a day and easily displace native vegetation. Dying back in winter, it leaves bare soil which, if washed out, can spread downstream. Where large stands of the plant persist on river banks there is an increased sediment input into the river. In slow moving waters this silt will accumulate and smother the riverbed, rendering the habitat unsuitable for fish spawning.

We asked volunteers to survey for giant rhubarb (gunnera tinctoria) for the first time, because it has been found in other parts of the UK. Giant rhubarb is an ornamental plant originally found in Chile and Argentina which thrives in streams or roadsides, liking damp conditions.

This plant’s wide leaf span and large dense stands can have a dramatic impact on the local biodiversity by excluding light. On rivers it causes erosion to banks, exposing them to fast running water after die-back in winter. Identified as a non-native invasive species, it is illegal to knowingly allow it to spread outside a property.

Parrots feather’s rapid growth means it quickly outcompetes native vegetation, forming mats and blocking sunlight and depleting oxygen levels for river wildlife. Left to spread in the wild we’re likely to see an increasing area of land lost to grazing as well as significant impacts on our biodiversity and road-side drains.

Similarly, New Zealand pigmy weed likes garden ponds. It also harms the growth of native vegetation in rivers forming a dense mat and reducing food, shelter and refuge for aquatic species.

Rachael Edwards, Volunteer Officer for SERT, said: “The efforts of volunteers as they walk along riverbanks looking for these species will really have a big impact on the action plan we, as hosts of the Wandle catchment partnership, can put together to tackle INNS for many years to come. We will then be able to focus our efforts on problem areas and know where, for example, to focus our efforts for our popular ‘balsam bashes’.”

Explaining the Goat Bridge weir project

One of our last events in Wandle Fortnight was to talk to residents about a project to lower the weir at Goat Bridge and make changes to the river channel, improving a section at Mitcham for wildlife.

Explaining the Goat Bridge weir and restoration project to residents — Explaining the Goat Bridge weir project to residents

Nearly 30 people attended our community event where partners from Thames Water, the London Borough of Sutton, the Environment Agency and engineering consultancy Mott MacDonald explained the project at a nearby community centre and by conducting tours of the area.

The key reason for lowering the weir and installing rock ramps and bed check weirs is to make this part of the Wandle passable for fish. At present it is totally impassible.

Currently, the weir leaves about a 500m section of the River Wande with conditions akin to a lake, as opposed to a flowing river.

Work on the project is scheduled to begin later this autumn.

Full details about the project and its benefits to the river can be found on our dedicated web page.

Our video shows how the weir at Goat Bridge creates a barrier to fish passage.

Natural England funds will bring back water voles, eels and trout to the Hogsmill

Posted on 21 September 2023 by Ian Lamont

The South East Rivers Trust (SERT) has been awarded £393,000 as part of Natural England’s Species Recovery Programme, which aims to support targeted action to recover the UK’s most endangered species.

On 14th September, 2023, Natural England chose SERT to host the scheme’s launch at the Hogsmill Stepping Stones in Ewell, Surrey, where the fortunes of water voles, eels and trout will be boosted by the project.

A total of 63 projects across the country have been awarded a share of £14.5 million by Natural England to help recover 150 species nationwide. Following a competitive application round, the money will be used by environmental charities, wildlife organisations, local authorities and charities to deliver the Nature Recovery Network.

Launch of the WET Hogs project — Citizen Zoo demonstrate a water vole realise box at the launch of the Natural Species Recovery Programme

The funding supports propagation, captive rearing, translocations, research and solution-trialling to find the best approaches to enable endangered wildlife to survive and flourish.

Some of the UK’s most iconic river wildlife has been in severe decline for decades, but now thanks to a generous grant awarded to SERT by Natural England, outcomes for rare and endangered wildlife and their habitat are about to improve on the Hogsmill river in South West London.

The WET Hogsmill project led by the South East Rivers Trust, will improve the habitat of the Hogsmill river, a chalk stream in South West London. There are only around 220 chalk streams worldwide meaning that this is an exceedingly rare and special habitat. The project will reintroduce Water Voles onto the river and create new habitats for both European Eel and Brown/Sea Trout. The project will run until Spring 2025.

Water quality testing on the Hogsmill at the Natural Species recovery programme launch

Co-CEO of SERT, Dr Bella Davies said “We are thrilled to have been successful in our application to Natural England’s Species Recovery Grant to support the recovery of water voles, eels and native wild trout which have become near extinct on the Hogsmill river in South West London. The Hogsmill is a rare urban chalk stream meaning that it’s important for nature and an important resource for people too.

“Our project will restore river habitat and create backwaters where fish can take refuge from pollution by creating wetlands to improve water quality which will help reintroduce Water Voles which were once prevalent on the river. We are excited to see this much needed work begin on the ground to bring Water Vole, European Eel and Brown/Sea Trout back to the Hogsmill.”

The Hogsmill river is the first tributary of the non-tidal river Thames and a chalk stream making it a UK Biodiversity Action Plan Priority habitat. Despite its rarity and importance, the Hogsmill has suffered a wide range of pressures leading to decline and loss of habitats and species over the last century and beyond.

Water Vole numbers have declined sharply since the end of the 20th Century making them currently the UK’s fastest declining mammal with a 97% decrease in population. Once ubiquitous and found in their millions, they are now considered to be on the brink of extinction. Water Voles were once prolific on the Hogsmill but became locally extinct in 2017.

Partnering with Citizen Zoo, a conservation charity, SERT will release 150 Water Voles across two sites on the Hogsmill, supplementing 101 Water Voles previously released by Citizen Zoo in 2022. This will help to increase the genetic diversity of the population.

European Eel are also critically endangered with levels declining by 90-98% from historic figures. Eels migrate up rivers during their life span and recent surveys on the upper Hogsmill recorded just one eel in 2016 and three in 2022. The WET Hogsmill project will support the creation of a large wetland and backwater while also creating a more complex instream habitat which is favoured by European Eel.

Trout have been extinct on the Hogsmill since the 1900s, owing to 19 predominantly obsolete weirs barring their passage, and preventing them from reaching critical spawning grounds in the river’s headwaters. Over the past decade SERT has made 18 of these weirs passable for fish and other species by either removing them or installing technical fish passes or easements. In 2024 the final remaining weir will be made passable for multiple fish species including Brown/Sea Trout and European Eel. By spring 2025 these fish will once again be able to access and migrate throughout the whole river for the first time in over 200 years.

SERT will provide a wide range of complementary community education and engagement activities for members of the public, schools and local businesses. Planned activities include installation of an interactive nature trail, indoor and outdoor education sessions, and community talks to help local people and businesses understand how they can help protect rivers and wildlife.

There will also be several opportunities to volunteer. Those interested to learn more about the project and volunteering activities can sign up to our newsletter or bookmark our events calendar for more information.

Watch our Co-CEO Dr Bella Davies explain how the project will help species in the Hogsmill.

Making a Wish come true for fish

Posted on 21 September 2023 by Ian Lamont

Luke Beckett, one of our assistant project officers, reports on our latest river restoration work on the Blackwater Restoration Project. This has improved the ability of fish to move along the river, opening up a 4.5km stretch known as the Wish Stream tributary, where it meets the River Blackwater, in the north Hampshire stretch of the River Loddon.

Helping fish move between river sections

Concrete shelf in the way — A concrete shelf, just visible below the water, made it difficult for fish to pass when the water flow is low

This was my first fish passage improvement since joining the South East Rivers Trust, so it was particularly fulfilling to deliver this work, which will help fish pass between the two watercourses and access good spawning habitat.

The River Blackwater, a tributary of the River Loddon which stretches across parts of Hampshire, Berkshire and Surrey, has long suffered from ‘poor’ fish classification status and only recently gained ‘good’ status. We aim to maintain or even exceed this status in the future and one way to contribute towards this is by improving the ability for fish to move easily between different sections.

The Wish Stream is an important semi-rural tributary of the River Blackwater, which supports a population of brown trout (Salmo trutta) and offers good spawning habitat in its lower reaches. Subsequently, improving connectivity between the Wish Stream and the River Blackwater is important for ensuring resilient fish populations in the catchment.

At the confluence of the two watercourses, we identified a concrete shelf which poses an obstruction to fish and eel movement, particularly during low-flow conditions.

Sloping notch and coping stones

Coping stones added to the river — The coping stones were added to the river, above the concrete shelf

The concrete shelf reduced the water depth, making it too shallow for fish to pass over. It also created a small weir between the Wish Stream and the River Blackwater during low-flow conditions, preventing fish moving up into the tributary. The smooth concrete also made it difficult for European eels to move along the river. This critically endangered species requires rougher substrates and slower flowing water to migrate along rivers.

Wish Stream brush and notch — An eel brush (right) and notch improve fish passage on the Wish Stream

To make this confluence more fish friendly, we created a sloping notch/ramp down the front of the concrete, allowing water to flow more naturally. The concrete was particularly hard – too hard for our machines and so we had to return with a hydraulic breaker to finish the notch.

In addition to this, we installed coping stones along the edge of the concrete to increase water depth over the shelf, enabling fish species to swim through. Finally, we improved the climbing substrate for European eels by adding an eel brush over the crest of the coping stones and safely down onto the concrete bed and vegetation upstream.

This passage improvement work was a relatively simple and straightforward delivery project. Most of it was completed in just over a day, although we had to wait until conditions were right to complete the final notch, and we were able to use coping stones which were left over from a previous project.

Great for brown trout and eels

The work enables fish, such as brown trout and European eels, to access important habitat for spawning and juvenile recruitment along the Wish Stream, which is roughly a 4.5km stretch of waterway.

It also allows mature individuals to disperse down into the River Blackwater and mix with other populations. With improved access to these habitats, fish numbers will hopefully increase and provide a greater prey source for other species such as kingfishers and herons.

Such improvement works show that sometimes it doesn’t take much to connect habitat and improve conditions for a range of species. I am looking forward to returning over the coming months to see these benefits. We hope this enhanced connectivity will strengthen fish populations in the catchment long into the future and I hope this is my first of many fish passage improvement deliveries.

How weirs affect rivers

Posted on 4 July 2023 by Ian Lamont

In the first of two blogs, Dr Chris Gardner, head of our Science and Partnerships team, outlines some of the problems caused by weirs on habitats and fish. This has a particular focus on the River Darent in Kent, where we have recently carried out several pieces of work as we try to help fish species move along the whole river catchment.

Restoring rivers to help wildlife

The term “river restoration” describes a set of activities that help improve the environmental health of a river or stream. These activities aim to restore the natural state and functionality of the river system to promote improved fish populations, biodiversity, recreation, flood management and development.

Restoration tends to focus on increasing habitat quality and diversity. A popular first step to achieving this is to overcome barriers such as weirs, increasing the access animals have to the existing range of habitats available in the catchment.

Over the centuries, we have adapted rivers for our own use, modifying them to facilitate land use for agriculture and development, navigation, water supply, power generation and other priorities.

Fish and other aquatic organisms evolved in rivers long before humans had this influence, and so they have not adapted to the modifications we have made, such as concrete banks, deep dredged sections, straight uniform channels and weirs, all of which block their passage.

Weirs impact rivers in three main ways

Habitat fragmentation

This is frequently caused by human activities which disrupt the continuity of habitats used by wildlife and is a land conservation issue as well as an aquatic one. Habitats which were once continuous become divided into separate fragments, restricting the movements of organisms (for example fish) and separating them from habitats, natural resources and other fish required for their survival or the completion of their life-cycle.

Fragmented habitats are also less resilient, preventing re-colonisation after pollution incidents and lowering genetic variability because of the restricted, effective population size, potentially placing populations at an evolutionary disadvantage.

River habitat

This is degraded in quality because an enclosed – or “impounded” – area is created upstream. In other words, river-like habitats become lake-like – stiller, with less water flow than a natural river should be. This drowns out natural features such as riffles (a shallow place in a river where water flows quickly past rocks) causing the loss of important spawning and nursery habitats for river fishes, thus lowering the numbers of fish and breeding success.

Rivers are naturally dynamic with erosion and deposition occurring in balance, creating a highly varied mosaic of temporal micro-habitats for all life-stages of fishes.

An impounded, or enclosed, section of river — An impounded area of river above a large sluice/weir on the River Medway. The river becomes still, affecting vegetation and animals

Weirs stop this natural tendency for change, creating a uniform, static environment. Upstream, an over deep river channel, similar to a lowland river, is formed in the impounded area, which might be inappropriate for the fish community (for instance, barbel habitat may become bream habitat). Impoundments also alter the temperature regime, oxygen content and cause sediment build up (siltation) in the upstream impounded area.

Sediment transport

Natural processes, such as moving sediment along a river, are prevented by weirs and instead the sediment stays in one place, covering the riverbed. This inhibits the riverbed’s function as a feeding and breeding ground. In a natural river, sediment (for example gravel) is shaped and sorted by water flow patterns. This creates a large diversity of ever-changing habitat types that support a rich diversity of wildlife.

Weirs stop natural processes and impact river channels in two main ways:

1. Upstream – Sediment transport is interrupted by the weir. Instead, it accumulates upstream. The lack of energy in the impounded area causes the sediment to not be shaped and sorted by the water flow and therefore creates a uniform habitat that supports less diversity of wildlife.
2. Downstream – Sediment transport is interrupted by the weir, reducing the supply of sediment (for example gravel) to the downstream reach, which is vital for creating habitat features for wildlife. This lack of sediment from upstream leads to increased erosion of riverbanks and riverbed, leading to “channel incision”. This is when the river begins at one height and cuts downward (incises) through its bed while leaving its floodplain behind [higher up] throughout its course.

Incised channels have knock-on impacts for:

Free flowing with riffles — A section of free-flowing River Darent at Shoreham. Shallow gravel riffles supporting abundant growth of Water Crowfoot, ideal spawning and nursey habitat for native brown trout.

Ecology:

The incised channel only connects to its floodplain in extreme flood events, when higher than normal water velocity is maintained in-channel during small to medium flood events. Aquatic wildlife, such as juvenile fishes, may become swept downstream during high flow events. The steep banks also cause a lack of marginal transitional habitats which provide a refuge for wildlife in flood conditions.

Flooding downstream:

Flood risk may increase downstream, again caused because the incised channel cannot connect to its floodplain other than during extreme flood events. The problem is simply shifted downstream.

Addressing the impacts of weirs

Removal of the weir should always be the considered as the preferred option, which solves all the issues described above. However, total removal is often not possible because of the way the landscape has developed since the weir was built.

Other factors that need to be considered include the wishes of landowners and river users, such as anglers, who might value the weir and its effect on the river.

The next best option might be a partial removal (lowering of the weir) and/or the implementation of a fish passage, which solves part of one problem (reducing the impounded reach) and all of another (connecting the upstream and downstream habitats). Fish passage solutions include natural bypass channels (which are preferred as they create additional habitat) rock ramps and baffles, as installed in 2023 by SERT at the Quester weir.

Essentially, any “solution” needs to provide fish with free movement and suit a range of fish sizes and flow speeds and depths that might be experienced at various times of the year.

Natural bypass around a weir — A natural bypass channel around an impassable weir on the River Darent, at Sundridge, Kent.

It also need to be delivered with usually tight budgets available.

Modelling, using an existing locally specific Environment Agency flood model is used to satisfy these needs and ensures no increase in flood risk for any nearby residential properties.

This approach is best practice and gives all interested parties the confidence to implement solutions with the simplest, and most cost effective design.

In the past few years, we have carried out several projects to improve passage for fish along the River Darent. This started with the removal of a large weir as part of the Acacia Hall River Restoration, completed in 2021. We have more recently installed an eel pass at the Questor weir in March 2022 and, in spring 2023, we constructed a fish pass using staggered baffles on the same estate.

What have The Sea Trout ever done for us?

Posted on 26 January 202321 March 2023 by Ian Lamont

To paraphrase Monty Python’s Life of Brian, what have sea trout ever done for us? They haven’t built any aqueducts, roads or made any wine…. but scientific research has demonstrated just how important they are in maintaining freshwater resident brown trout populations.

Enabling migratory sea trout to return to their spawning areas is just one reason freshwater conservationists work to improve fish passage and the ecological connectivity of rivers.

The South East Rivers Trust’s head of Science and Partnerships, Dr Chris Gardner, illustrates below an example of the trout to underline the importance of overcoming barriers to fish migration.

Beginning of the end for balsam bashing?

Posted on 17 October 202219 October 2022 by Ian Lamont

The battle to remove Himalayan Balsam from riverbanks by hand has become a staple activity of river conservation management. This invasive non-native species returns annually – and spreads profusely.

However, a biological method of tackling it could eventually rid our rivers of it completely. Nicky Scott, our Volunteer and Engagement Officer, reports the initial results of a trial on the River Hogsmill.

Connecting the dots: Understanding what landscape recovery schemes could look like

Posted on 28 May 20224 July 2022 by Ian Lamont

Bringing landowners together through a series of workshops and site visits has opened inspiring conversations about what the future of nature-based solutions at catchment scale could look like.

Kathi Bauer, our Natural Capital Co-ordinator, writes an update on the South East Rivers Trust’s work on a national trial, funded by DEFRA, for the new agricultural subsidies programme – Environmental Land Management Schemes (ELMS).

Making a difference during Loddon Rivers Week

Posted on 5 October 202114 February 2022 by Ian Lamont

Almost a year to the day that the South East Rivers Trust constructed a backwater on the River Loddon in Charvil Meadows, we were back to do further enhancements as part of Loddon Rivers Week 2021.

This was just one of a series of river work that took place during this celebration of the River Loddon and its tributaries, between 18th-26th September. The work to co-ordinate the week was funded by the Environment Agency.

During the week, volunteers planted native plants to stabilise the banks of the previously constructed backwater, put in gravel to a chalk stream, tackled invasive species and enjoyed learning about bats.

Several partners were involved in the week, including Hampshire and Isle of Wight Wildlife Trust, the Loddon Fisheries and Conservation Consultative, Blackwater Valley Countryside Partnership, Hampshire County Council and Dinton Pastures County Park.

Nature based solutions to man-made problems

Posted on 5 May 202112 October 2023 by Samantha Hughes

There is no doubt that we are going through a massive and positive paradigm shift. It is finally hitting home that human activities thoroughly depend on the health of the natural environment and the sustainability of the many services it provides. The natural environment has rapidly moved from the periphery to the very centre of conversations, with action on fundamental issues from our own well-being to agriculture and the economy.

Humans are an increasingly urban species, although a major consequence of the COVID-19 pandemic is how we have come to realise the importance on being in contact with Nature, and how Nature can provide us with many solutions to the problems we create.

One of those problems is road runoff. Most of us are highly dependent upon cars or other vehicles and the massive road network carved into our catchments, to get us or the goods we buy from one place to another.

Grand opening of Acacia

Posted on 14 April 202114 February 2022 by Samantha Hughes

The Central Park/ Acacia Hall River Restoration Project took a massive step forward at the end of March, writes Sam Hughes.

On Thursday 25^th March 2021, after months of delay because of the pandemic, the (rather ugly but essential) cofferdams were removed from the upstream and downstream ends of the project area, and flow was returned to the restored western channel of the Darent that runs through Central Park then past the redeveloped Acacia Hall.

I can’t tell you how excited the SERT team is about this, after more than three years of hard and very muddy work!

SERT on tour – delivering a fish passage project on the River Ock

Posted on 7 November 20203 February 2022 by Ian Lamont

In September 2020, we successfully installed two fish passes on a weir on the River Ock in Abingdon. The River Ock is a small tributary of the Thames and owes its name to the pre-Saxon word “Ock” meaning young salmon. Salmon were a common sight on the Ock and a staple part of local diets in the middle ages. So why are these migratory majesties no longer present on the river?

Aside from other more global issues, barriers to migration such as the weir at Abingdon would present challenges to upstream migration of all fish species, not just salmon. The weir results in fragmented habitat which in turn can create bottlenecks at varying life stages. As a result, the survival and success of fish is compromised. It was therefore in the river’s best interest to implement fish passage on this weir.

The weir is a standard crump gauging weir, used by the Environment Agency’s Hydrometry and Telemetry’s team to monitor flows in order to help predict downstream flooding and manage abstraction licenses. It is 5.7m long and split into two channels. The left hand channel (as you look downstream) feeds the River Ock and the right hand channel feeds the Sandford Brook. The design of the weir, coupled with the fact that it was a gauging station, added several complexities.

Eat, Sleep, Restore, Repeat

Posted on 18 April 202014 February 2022 by Ian Lamont

Our volunteers were incredibly busy back in February 2020, carrying out River Restoration on the Beverley Brook and Wandle.

At the start of 2020, a new group of volunteer River Restorers came together to learn about natural river processes and how heavily modified waterbodies (such as the Beverley Brook) have been altered over time. These changes stop the natural processes which would usually shape a healthy river ecosystem, leaving us with a degraded river that has few, good habitats for wildlife.

Early in 2019, we carried out a large-scale restoration project along 1.3 km of the Beverley Brook through Wimbledon Common. Our River Restorer volunteers came on board to help us extend the work upstream – this time using people power alone!

We worked together to plan and design the work, ready to deliver as a team in mid-February.

Acacia Hall – River Darent Restoration

Posted on 18 April 202014 February 2022 by Samantha Hughes

Having completed most of the river works on the River Darent in Central Park, Dartford in January 2020, we now have a bit of time to tell you what we got up to!

The River Darent splits immediately upstream of Dartford Central Park.

The western channel meanders through the park and past Acacia Hall weir before disappearing under an old ballroom building and the A226 before continuing through Dartford Town Centre. The eastern channel acts as flood relief channel and, prior to the restoration project, took the majority of low to medium flows.