Volunteers will have the chance to help revitalise wetlands in Riverside Gardens, Bromley, for river wildlife thanks to a grant from the Mayor of London.
The Riverside Gardens Wetland Restoration project will be managed by the South East Rivers Trust (SERT) in partnership with the London Borough of Bromley and local community groups.
It aims to improve water quality and habitat in the headwaters of the River Cray, the prime chalk river of outer, south east Greater London which rises in Orpington.
Announced on Wednesday (13th March), the Bromley project is one of 21 that will receive a grant from the Rewild London Fund.
This is aimed at making the capital more resilient to climate change by improving 40 Sites of Importance for Nature Conservation (SINCs).
Currently, this stretch of the river suffers from high sediment input which is detrimental to chalk streams and its wildlife, and the wetland is choked with scrub. The project, supported by the Mayor of London in partnership with the London Wildlife Trust, will reprofile the inlet channel and the online wetland and add a new sediment trap to prevent sediment being released downstream. This will increase the water quality and flow to support aquatic vegetation, fish and river invertebrates.
Part of the site for the Riverside Gardens project in Bromley
Volunteers will have the chance to plant up the reprofiled wetland, using a selection of native wetland plants.
Petra Sovic Davies, Senior Catchment Manager at SERT, said: “We are delighted to receive funding to help us restore the Riverside Gardens Wetland, especially as it will allow us to involve the local community. It is so vital that residents are involved in being given the chance to look after their local natural space. A thriving wetland not only acts as a magnet for wildlife but also provides a wonderful open space that people can enjoy and where they can learn about the natural world.”
The Mayor of London, Sadiq Khan said: “This new rewilding funding will support the restoration of some amazing spaces in the capital, enabling Londoners to benefit from nature on their doorstep and help us to combat the impacts of climate change.
“I believe that all Londoners should be able to enjoy green spaces and that access to nature is a social justice issue. So I’m doing all I can to ensure that Londoners can enjoy wildlife wherever they are in the city.”
Pollution in the Hogsmill River, by Toby Hull of the South East Rivers Trust
Brace yourselves: 0% of England’s rivers are in good overall health. A truly shocking fact for a habitat that’s so vital to all of us.
This and other alarming statistics come from the Rivers Trust’s 2024 State Of Our Rivers Report, which has been launched today (Monday 26th February).
Combining data, insightful maps, and illuminating case studies, the report dives into the data and evidence, offering us an insight into just how our rivers in the UK and Ireland are doing.
The data is clear:
No single stretch of river in England is in good overall health
Just 15% of English river stretches reach good ecological health standards
Toxic chemicals that remain in our ecosystems for decades pollute every stretch of English rivers
Healthy rivers can be a powerful ally in mitigating the effects of climate change, being able to protect communities from flood and drought, the report emphasises. They support a wealth of biodiversity. They also benefit our physical and mental well-being and are a fantastic way for us to reconnect with nature.
However, these vital ecosystems are plagued by sewage, chemical, nutrient and plastic pollution. They have been heavily modified, so they don’t function as naturally as they should.
All this means that our aquatic wildlife, from plants to fish, is having to work harder to survive – and that rivers can be unpleasant places to visit or to use for recreation.
So, what can you do? Here’s five actions you can take
1 Write to your MP to demand meaningful action
Demand better for your river
If you are shocked by the state of our rivers, write to your MP to demand change.
Tell them that restoring rivers is climate action, supports wildlife and protects communities.
The report allows you to search for your local stretch of river and use its stats and maps on sewage, barriers in rivers and chemicals to arm yourself with facts before contacting your MP.
You can contact your MP via the Rivers Trust’s portal – and add your own words to the template.
Ask your elected representative what they are doing about river health. We want you to demand better Government action for our rivers, through better water quality monitoring, investment in infrastructure for sewage treatment and better funding for Nature-based Solutions.
To help you when you write, we have compiled a State Of Our Rivers Catchment Crib Sheet with a basic comparison of Water Framework Directive ratings for our catchments between 2019 and 2022.
We would also encourage you to speak up for some of our recent work (below) and show how it is making a real difference to rivers.
For example:
Volunteers plant up berms at Morden Hall Park in September 2023
Nature-based solutions such as leaky woody dams are holding water longer in the landscape of the Beult area of the River Medway. This increases biodiversity and helps nature thrive, as well as slows water flow into the main river, where it is abstracted for human use. As those who went on our Nature-based Safari concluded: We need to make more of this happen on a wider scale.
Deflectors and planted berms extending parts of the bank have re-wiggled a straight section of the River Wandle in Morden Hall Park (pictured). This works wonders for wildlife, varying the flow of the water and giving fish and invertebrates places of refuge and areas to breed.
New wetlands constructed at Chamber Mead have brought fresh hope to the Hogsmill. They divert pollution which will help protect 5km of precious chalk stream.
Our Holistic Water for Horticulture project works with growers towards a 2030 target that 50% of the UK’s fresh food is sourced from areas with sustainable water management. The south east is an area already classed as water-stressed and this is an issue that affects our food security.
We’re also working to put rivers at the heart of landowner thinking as part of the Darent Landscape Recovery Project, a Government-funded pilot.
2 Shout out for your local river on social media
Join the fight for healthy rivers
What’s your local stretch of river? How do you use it and how does it affect your mood? Perhaps you visit it for pleasure with your dog on a daily walk, or use it for recreation such as rowing, canoeing or swimming.
However you care about your local river and interact with it, we want you to tell us online. Once you have found out about the condition of your local river via the State of Our Rivers report, make a noise about it!
Report what you see – for good or bad – whether that’s young fish thriving and wildlife flourishing, or plastic pollution and sewage outfall spills.
Use the hashtag #StateofOurRivers and find us on X (formerly Twitter), Facebook and Instagram. Why not tag the elected representative you have emailed, too? You can also tag @TheRiversTrust on all channels.
3 Sign up to be an Everyday River Hero
Whether you are a seasoned, long-term river user or you’ve been caught up in the increasing wave of publicity around sewage and other river issues, we want you to become an Everyday River Hero.
It might be hard to believe given our wet winter, but the south east of England actually receives less annual rainfall than the south of France. We face a real threat of not being able to meet supply by 2050, because of a growing population and climate change.
Launched in January, our 10-week email programme will tell you why rivers are essential for our daily lives and how to care for and protect wildlife, when you are exploring the great outdoors or at home. How – and how much – water you use in your bathroom and kitchen, as well as your garden can be as vital for rivers and the wildlife that thrives in them as the flea treatments you use on your dogs.
We always get a huge thrill when we can involve volunteers directly in work to help rivers thrive. There is nothing like enabling communities to take action for the stretch of water they love.
Help install gravel on the River Blackwater in Aldershot. Join us to improve this stretch of the River Loddon for fish and invertebrates on any of four days, from March 12th to 15th.
Sign up for Outfall Safari training on the Beverley Brook, on 20th. Join us and the Zoological Society of London to learn to spot and report misconnected plumbing that is polluting rivers. The results will help trace appliances such as washing machines that have been connected to the wrong pipes when they were installed.
To book, visit our events page – and bookmark it for subsequent volunteering opportunities during 2024.
5 Book our education sessions for your school or youth group
A school education session
Educating our youngest citizens is a core part of our work on the Beverley Brook, Hogsmill and Wandle rivers, where we hold sessions for Key Stage 1 and 2, in schools and along rivers. Our sessions are available for youth groups, too, so inspire them to cherish their local waterway by booking a session.
We also run school sessions on the River Mole, under the Our River Our Water programme.
If you are a parent or teacher, read our education page for full details and encourage your school community to get in touch!
As one teacher said about our curriculum linked sessions: “They fit exactly with what we have been learning and the children enjoyed all the activities.”
A new online tool has been launched this week to help tackle road runoff pollution in London’s rivers by highlighting the best places to install nature-based solutions such as wetlands.
The development of the first-of-its-kind tool by Thames21 builds on years of research by the environmental charity and its partners Middlesex University and the South East Rivers Trust, which contributed with mapping, scoping and reporting.
Pollution from our roads adds to a number of problems for our rivers coming from sewer overflows, litter and misconnected drains. However it is often the Cinderella of pollution topics, because it receives far less public attention than sewage or agricultural causes.
Research from the Rivers Trust shows that the UK’s 1,600 rivers are affected by a cocktail of chemicals that are speeding up aquatic nature-loss, affecting insects, birds and mammals.
Road runoff goes straight to rivers
Road runoff can contain residue from oil spills, as well as tyre and brake wear from vehicles. These build up during dry weather and are then washed into rivers and streams when it rains.
The new tool will help decision makers prioritise the right water quality improvements:
in greenspaces that lie between the road and the river
at road locations in Outer London where surface water drains to the rivers; and
on London’s main strategic road network (includes Transport for London’s roads and some sections of National Highways’ and local authority roads)
Thames21 started its initial road runoff project identifying key polluting roads in 2019, with funding from the Mayor of London, Transport for London, and the Environment Agency. The British Geological Survey built the online decision support tool ‘Road Pollution Solutions’ and provided some additional support through the UKRI NERC-funded CAMELLIA project.
The South East Rivers Trust contributed research on sites in South London, including Surbiton, using its GIS mapping technology and catchment-based approach, identifying places where solutions such as wetlands could be built to counter the pollutants. By providing a natural barrier and filter using nature-based solutions, some of this road runoff pollution can be captured and prevented from entering rivers in the first place.
Users of the tool can search different boroughs, pinpoint particular areas and see just how polluting they are. This will help to prioritise where solutions could be put in place as mitigation. The tool shows the location of rivers, sewage outfalls and areas that drain into waterways.
An example of how the road runoff solutions user guide works
Modelling has shown that 2,415 road sections covering a total of 451.43km of London’s roads assessed pose a high risk of causing road runoff and are therefore a priority. Roads where heavy goods vehicles regularly apply their brakes are often the worst affected.
Community groups can also easily see pollution hotspots and help to suggest solutions by working for example with the authorities or through catchment partnerships.
The tool – which extends to all outer London boroughs – allows uses to access data by boroughs or river catchment and includes the Wandle, Beverley Brook, Hogsmill, Upper Darent, Lower Cray and Upper Cray.
Working in partnership, authorities responsible for these roads could intervene by providing nature-based solutions in these areas to help make runoff cleaner, and improve water quality in local rivers and watercourses.
Find out how the tool works by reading the user guide.
The South East Rivers Trust regularly works towards removing weirs or installing fish passes. In the second of a series of blogs about the problems weirs cause to rivers, Dr Chris Gardner, Head of Science and Partnerships, writes about two big issues. These are the movements of fish (which he tracked for his PhD) and drought resilience. Here, he addresses some myths about both aspects.
‘Migratory’ fish? All fish migrate
It is often thought that weirs and other barriers that restrict the movement of fish only affects ‘migratory’ species such as salmon, sea/brown trout and eels, as their migrations are relatively easy to observe and are well known.
A proportion of brown trout will migrate to sea and return as sea trout if their migratory pathway is unimpeded. Returning sea trout are very important in maintaining brown trout populations.
However, all fish migrate to some extent, and all fish have life stage specific habitat requirements affected by habitat degradation. Coarse (or freshwater) species such as barbel, chub and dace are affected by habitat fragmentation and degradation caused by weirs.
Higher water velocities on riffles encourages plants such as water crowfoot to grow. Plant growth on riffles makes it difficult for predatory fish to hunt. This also provides an abundant food supply of invertebrates and overhead cover that hides fish from predatory birds and animals.
Riffles are great places for baby trout and young salmon to live, they are also the preferred habitat for juvenile barbel. However, riffles hidden under lake-like habitats upstream of a weir lack the characteristics that make them great juvenile barbel habitats. And if there are low numbers of small barbel then there will be fewer numbers of big barbel and eventually no barbel at all.
Here, the trout and salmon fraternity are ahead of the game. The economic value of salmon (commercial and recreational) and the large declines in salmon populations since the 1980s have caused scientists and anglers alike to research and understand what the habitat requirements are for all life stages of these fish.
They have used this information to minimise potential population bottlenecks or limiting factors because of available habitat. There are many things impacting our fish populations, but in-river habitat is the one thing that is relatively easy to address and benefits all wildlife. Organisations such as the Wild Trout Trust have been encouraging progressive thinking and educating game anglers in fisheries management and river restoration.
Research shows why fish need to access the whole river
Coarse fish migrate and need to move around a river system to locate specialised habitats required at certain times and during certain conditions. Fish are streamlined, live in a near weightless and frictionless environment and need to constantly swim just to maintain a static position in the river. Hence, fish have great potential to be highly mobile.
Modern tracking studies using implanted radio or acoustic tags have revealed these migrations. For example, in 2010 Dr Karen Twine, of the Environment Agency, radio tracked 20 adult barbel (6-15lb) in an 8.2km reach (between two impassable weirs) of the Great Ouse for 18 months. She demonstrated that the barbel utilised most of the river length available to them and made seasonal movements to spawning and over wintering habitats.
Barbel migrate and use different habitats at different times of year and at different stages in their lives
Similarly, in 1993 Dr Martyn Lucas, of Durham University, radio tracked 31 adult barbel (2-6lb) over 15 months in a 7.2km reach of the River Nidd, a tributary of the Yorkshire Ouse, with open access to the Ouse.
Again, these fish were highly mobile, ranging over sections of river from 2-20km in length. Their movements were associated with seasonal shifts in habitat, upstream spawning migrations and their downstream migrations to ‘over wintering’ habitats in the lower reaches and main River Ouse.
Basically, fish will move as far as they are able to fully exploit the best available habitat/resources: the more limited the resources, the further they will travel.
Other studies on less fragmented rivers with more limited essential habitats have shown that fish have the potential to move over very long distances.
Study shows the benefits of free passage
During my PhD in 2006, I tracked the movements of 80+ adult common bream (4-7lb) over four years in a long 40km reach of the Lower River Witham, a very uniform fenland river in Lincolnshire.
Returning a tagged common bream to the River Witham during my PhD, to demonstrate how mobile fish can be in open, barrier free habitats
My bream were tightly shoaled and relatively immobile in a deep tributary off the main river at the upstream extent of the reach during the winter, moving short distances of, on average, less than 5km a month up and downstream.
In the spring, they became highly mobile moving on average 30-40km a month, utilising the entire length of the river available, with one individual moving more than 120km in a single month!
At this time, they were visiting shallow tributaries off the main river, before using these for spawning in late May/early June. Once they had spawned, they spread out and spent the rest of the summer in the main river foraging, again moving on average 20-30km a month up and downstream. In the autumn, they moved back upstream to the deep tributary for the winter. This same yearly pattern was observed throughout the study.
These studies demonstrate that adult fish use different habitats at different times of the year and require free passage between them.
Habitat requirements are different for adult and juvenile fish. So, during a fish’s life it will have many different habitat requirements. These requirements will be more crucial for juvenile fishes because of their vulnerability to predators and therefore their need to find safe cover.
If any single habitat type is lacking, limiting or inaccessible, there will be consequences for individual survival and therefore the population as a whole. Weirs often restrict populations to those reaches that have sufficient habitats to enable life-cycle completion.
The “weirs” thing about drought resilience …
A common misconception is that weirs delay river discharge and therefore make the river more resilient to drought. Weirs do hold back a quantity of water in the upstream section, which is “impounded” – leaving the river more like a still canal or pond. However, a weir just stores water in the upstream area – and once the river is full, river flows over the weir at the same rate it enters the impoundment.
Imagine an impounded section of river as being like a kettle being filled from a tap. Once full, the kettle overflows at exactly the same rate as the tap runs and the water bill ticks up exactly the same.
A river in Kent that dried up in the summer of 2022
In the event of drought, rivers tend to dry from their upstream end first. Impoundments upstream of weirs can and do provide refuge areas for fish in such an event. However, these areas are likely to be heavily silted because of the lack of flow, and will quickly deoxygenate because of biological processes in the silt, leading to fish deaths.
Fish will move downstream naturally in response to a drying river using the river’s flow to navigate.
However, if the fish encounter an impoundment upstream of a weir, and there is no flow going over the weir (because of the drought), there will be no flow cues to navigate by and the fish will simply be unable to move any further and become trapped where they will die as the water in the impoundment deoxygenates.
If no weirs exist fish will move downstream, seeking out deeper, fresher water in the river’s lower reaches. Once the drought has broken, they will then move back upstream.
So, perhaps counterintuitively, weirs actually reduce a river’s resilience to drought.
In conclusion, the impacts caused by weirs are problems for freshwater fish as well as salmon and trout: the principles might not be as well understood or as popular, but they are real. If our rivers are to fulfil their ecological potential, we need to address this and other factors that are limiting fish populations.
River lovers are being urged to sign an open letter calling on all political parties to adopt a five-point plan for wildlife in their manifestos for the next General Election, likely to take place in 2024.
The Rivers Trust movement has joined an 80-strong coalition of partners to support the Nature 2030 Campaign. It is led by the Wildlife and Countryside Link and supported by celebrities including television personalities Steve Backshall and Chris Packham.
Research shows that the UK has become one of the most nature-depleted countries in the world, with more than one in seven native wildlife species facing extinction.
The campaign outlines that in 2022 sewage was discharged for more than 2.4 million hours across England, Scotland and Wales, accounting for more than 389,000 sewage spills. Commitments were set in 2021 to protect 30% of land and sea for nature by 2030, but there’s a long way to go to meet these targets. With only seven years to go, just 3% of land and 4% of sea have this protection. We need stronger environmental leadership and the Nature 2030 campaign demands it.
Thousands of people have already signed the letter, which was launched at Westminster in July.
As one of the largest regional rivers trusts, the South East Rivers Trust (SERT) is urging supporters to back the campaign, which has five key asks for political parties:
Double the wildlife-friendly farming budget to £6bn for ambitious farm improvements and large-scale nature restoration
Make polluters pay for nature restoration by requiring big businesses to deliver environmental improvement plans and funding to counter damage
Create green jobs on a large scale, including setting up a National Nature Service delivering wide-scale habitat restoration
Increase protection and funding for wildlife sites by creating a Public Nature Estate to fulfil the promise to protect 30% of the land and sea for nature by 2030
Set up a new law guaranteeing a right to a healthy environment, establishing a human right to clean air and water plus access to nature, plus building nature into decision making
Hester Liakos, co-CEO of SERT, said: “Rivers are at the heart of the battle to restore nature. Our work with local communities, farmers and landowners demonstrates the positive difference that nature based solutions and natural flood management can make in improving the health and biodiversity of rivers. But to make this difference on the scale that nature truly needs requires more funding and greater commitment and leadership from Government – so we’re asking our supporters to sign this open letter to demand action from all political leaders.”
Tessa Wardley, Director of Communications and Advocacy at the Rivers Trust, said: “The public are rightfully outraged by the state of our rivers and we need political parties to make firm commitments towards their recovery, which are then backed up by action. Delivering the Nature 2030 policies would significantly improve the health of our rivers, which are absolutely core to tackling the biodiversity, climate and wellbeing crises we face as a nation and planet.”
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
Tanners Weir at Sundridge on the River Darent, which is totally impassable by fish, fragmenting the habitat available for them to utilise
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 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:
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.
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:
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
The Brasted Lower Weir being removed by drill
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.
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.
The South East Rivers Trust (SERT) installed a “baffle” fish pass on the weir at the Questor industrial estate in Dartford in late April. Project officer Jack Hogan reports.
Over the past few years, we have been working to improve the lives of fish which need to move up and down the River Darent in Kent.
This began in 2021 when we completed our Acacia Hall River Restoration project in Central Park, Dartford. That project removed a large weir – a barrier to fish moving up and down the waterway – and transformed 600 metres of a silty backwater into a flowing natural river, improving both the ecology and beauty of the park.
The Acacia weir removal also opened up the way for migratory fish to undertake their journeys upstream – and salmon have already been spotted up the river beyond the project.
Our latest efforts have been at a weir a little way upstream from Central Park. Known as the “Questor weir”, it was an impassable obstacle for fish. It is long, wide, and gently sloping. This means that, for most of the time, the water that passed down it was just a skinny, shallow sheet in which no fish could have swum.
To help the fish overcome this, we designed, and have now installed, what is known as a baffle fish pass.
A baffle is defined as a device which regulates flow or passage. In this case, essentially it holds back water, becalming it and making it easier for fish to navigate. In doing so, the baffles increase the depth of water on the weir along each line of the section of river.
This results in a series of steps, or a series of rectangular ‘pools’. Breaks in the line of each baffle – known as notches – allow fish to pass between these areas of calmer water, from one ‘pool’ to another. The shapes of the baffles are also designed to reduce turbulence in the water, which helps ease the way upstream for even small fish.
Weir modifications
The concrete structure of the weir also had to be modified to allow the fish pass to function properly. At the downstream end, modifications had to be made to the bed of the weir in order for the final three rows of baffles to the installed.
Modifying the weir’s bed to slot the lower baffles into place
At the upstream end, the crest of the weir was also notched. This was done to ensure clear passage through the old steel and concrete crest, and to ensure that enough water flows down through the fish pass. A fish pass without water would be like a ladder without rungs!
What we have installed will be used to pass both up and downstream by everything from baby eels – or elvers – to larger fish such as salmon: and the weir, or rather the newly installed baffles, can serve as their ladder to the next step up the catchment. This work builds on the eel pass that we installed on the Darent in March 2022 and we are currently looking at future projects to further improve fish passage on this river.
SERT is developing other projects on sites all along the Darent which will, step by step, restore and reconnect fragmented habitats across the whole river catchment. Some sections of the river have become “impounded”, meaning they become stand-alone water bodies that are hemmed in by man-made objects such as weirs or dams.
Our video below shows how the flow of this section of river has been dramatically transformed from a rushing, single sheet of water into one that will help the survival of migratory fish.
We would like to thank WL West Sawmill in Petworth, who hand-picked some magnificent pieces of oak from which they cut our beautiful custom baffles for the lower end of the design. The rest of the baffles, made of recycled plastic, were donated by the Environment Agency.
Special thanks must also go to Chris at JLL for facilitating the work. Without cooperation from landowners and managers we couldn’t do good work for nature such as this.
We are also very grateful to everyone at Questor – in particular, the people at Daikin and Kent Powder Coating. They offered us forklift support on demand, saving our backs, and secure overnight storage for our equipment, proving that successful river restoration work always is a collaborative effort by many different groups.
Every five years, water companies in England are required to produce a Water Resources Management Plan (WRMP), which outlines how they intend to meet the expected water demands not just in the next five years but over the next 50 in their respective service areas.
These plans take into account increasing population, climate change and growing risks of drought – while also protecting and enhancing the local environment.
An important part of the WRMP plans is customer feedback on topics which concern them most. They are currently in draft form and out for public consultation.
Do you see drains – known as outfalls – spilling pollution into rivers when out on riverside walks? Do you know why this happens and would you like to help sort out the problem?
Our rivers should be healthy spaces for wildlife, but need protecting from many forms of pollution. One of them is household plumbing that is misconnected, meaning that foul water goes straight into the waterways through drains that should be connected to the sewage system.
This spring, river lovers along the Wandle and the Cray and Shuttle are being given the chance to train as citizen scientists to help rectify the problem in the latest roll out of the Outfall Safari programme.
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.
The South East Rivers Trust has launched a Chalk Streams Review, to ensure that all rivers and streams which qualify across our catchments are identified and mapped. Dr Chris Gardner, our Head of Science and Partnerships, sets out the plan and how the public can help.
The Central Park/ Acacia Hall River Restoration Project took a massive step forward at the end of March, writes Sam Hughes.
On Thursday 25th 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!
Raw sewage is entering UK rivers on a horrifyingly regular basis, damaging our river ecosystems and putting public health at risk. In 2019 alone, untreated sewage poured into England’s rivers for an astounding 1.5 million hours, over the course of 200,000 separate incidents.
What’s really shocking is that, much of the time, this practice is completely legal.
Across the UK is a network of Combined Sewer Overflows (CSOs). These are essentially Victorian-era relief valves on the sewage treatment infrastructure. If sewage piping, or even a sewage treatment works, is becoming overwhelmed with sewage and rainwater, it is diverted and discharged into a nearby watercourse instead of backing up into homes.
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.
The Riverside Gardens Wetland Restoration project will be managed by the South East Rivers Trust (SERT) in partnership with the London Borough of Bromley and local community groups.
