Category Archives: River Restoration

Richmond Park restoration: update two years on

It has now been two years since the river restoration work on the Beverley Brook through Richmond Park was completed. This time has allowed the two restored stretches with a cumulative length of 600 metres to adjust and naturalise in response to the changes which were made. The original blogs describing the works can be read in the links below.

http://www.southeastriverstrust.org/delivery-to-the-beverley-brook-in-richmond-park-phase-1/

http://www.southeastriverstrust.org/tree-planting-in-richmond-park/

http://www.southeastriverstrust.org/planting-on-the-beverley-brook/

A key principle behind the restoration was to reinstate natural processes back to the river by providing energy and diversity which in turn would allow it to ‘self-heal’. The river now has the opportunity to scour and erode the bed which consequently creates in-channel features such as pools, riffles and bars which were almost completely lacking before. The uniform sandy bed has been displaced to expose the rich gravels below, providing much improved conditions for invertebrates and fish spawning.

The bed now undulates ranging from ankle deep riffles to waist deep pools. There is now a huge array of flow types and with it a myriad of habitats. For the first time in decades the Beverley Brook is audible as the flows pass over, under and through the Large Woody Material and as it babbles over the riffles.

Large Woody Material narrowing the channel and kicking the flow around

With all this scour and erosion, sediment is being deposited in areas of slack water, such as on the inside of meanders and among the vast quantities of brash that was installed. This is working to such great effect that the brash in many locations is no longer perceivably brash. So much sediment and seeds have been deposited that these now appear to be natural banks which stabilise and help to narrow the channel to the dimensions that the Brook should naturally have. In turn, the vegetation that is establishing collects more silt, and so the channel continues to evolve and diversify.

A brash- berm on the left naturalising with a diverse mix of marginal plant species

The regraded banks and low lying berms are vegetating now that the erected fence keeps the deer and their intensive grazing habits out. Marginal and terrestrial plants are starting to thrive, providing previously absent habitats. The grass really is greener on the other side of the fence.

Follow up macrophyte, invertebrate and fish surveys will take place next summer. By then these communities will have had time to adjust enabling us to make an informed and scientific assessment of the biological impacts of the work. Until we get the results back, anecdotally we have observed significant changes. As previously described, the plant communities are noticeably diverse and extensive. Fish which were previously almost completely absent from the downstream stretch are now abundant with large shoals of dace, chub and stone loach being very apparent.

A picture describes a thousand words so I will keep the blog to a succinct length (for me anyway) with a selection of before and after shots to demonstrate the points raised above. We will keep you posted when we get the results of the follow up surveys.

Before; over-wide, straight, sandy bed and bland with few marginal plants…

and after two years later!!!

Before

Two years on.

Before

Two years on

Before

Two years on

 

A sandy bottom and over-wide channel

Two years on, gravel with marginal plants

An attractive functioning river returns to Richmond Park

River Club Weir Removal

1

No 12 on the Hogsmill obstruction hit list was the River Club weir.

With very shallow flows plunging over its crest, and a drop of 0.7 m between the upstream and downstream water levels, this weir on the Hogsmill near Tolworth was a complete barrier to fish passage under the majority of flow conditions. On each flank, the concrete and stone abutment walls were also structurally failing.

After lengthy discussions, in the course of which no justification for keeping or maintaining this weir could be established, we worked with the Environment Agency and Thames Rivers Trust to undertake a full weir removal.

2

Once we had accessed and prepared the worksite, we began breaking up the main part of the weir using a long reach excavator with a hydraulic breaker attachment. It’s amazing how solid parts of these structures are, but our operator Roo’s patience eventually prevailed!

3

Over 30 tonnes of concrete was removed from the channel and collected by a grab lorry.

4

The stone walls were then broken up, and the new bank profiles were installed using a range of sustainable and biodegradable materials.  Native marginal plants and seed were then added to the new banks, which over time will provide erosion control and great habitat.

5

6

It’s great to see the channel upstream already returning to a more natural state. Within a few days of removing the weir, a resident koi carp had moved from the upstream pool and was enjoying exploring some new habitat. This bodes well for all our native fish species we know are in other parts of the Hogsmill.

7

We had fantastic weather throughout the duration of the project, although we could really do with some rain, as most of the rivers across the South East of the UK are experiencing extreme drought conditions.

A big thanks goes to to our local Environment Agency staff, Thames Rivers Trust, The River Club, two very supportive landowners and Roo Newby for his excavator operating skills.

We’ll now be focusing on the six remaining obstructions to fish passage with our aim of restoring this lovely (previously neglected) river to a more natural and improved ecological state.

Why remove weirs? Some excellent diagrams on how weirs affect river habitat and geomorphology have been produced by the Wild Trout Trust and you can also read our article on how weirs affect fish communities.

Before and After photos

BEFORE AND AFTER 1

The Timelapse Video

Hogsmill reconnected to the Thames with new fish pass in Kingston

The Hogsmill gauging station is an Environment Agency flow monitoring structure, essential for water resources planning and regulation.  It is the furthermost downstream weir in the catchment and poses a significant barrier to fish passage, preventing the recolonisation of fish to the river from the Thames below. Addressing passage at this key site has been discussed for several years but due to the sensitivity and importance in the recorded flow-gauging data, in combination with the unconventional structure it has resulted in a complicated and extensive process to identify and develop a suitable solution. JBA have helped inform the positioning of the upper baffle and through a programme of spot gaugings will update the rating of the gauging station.

OLYMPUS DIGITAL CAMERA

The impassable Hogsmill Kingston gauging station

The selected approach is a variation on the Low Cost Baffle (LCB) Solution as we have used elsewhere, whereby rigid baffles are put on the downstream weir face in a specific geometry and spacing to slow the water, deepen the flow and provide a distinct passage route on the weir face. However, due to the significantly steeper gradient at the site in comparison to that the design was developed for, the Trust and EA have modified the arrangement to help promote the correct hydraulics to enable fish to pass.  The maths aside, in essence this meant that each line of baffles is incrementally taller than the last, starting at 120mm and ending at 288mm at the downstream end.

With this novel approach the Trust and the Environment Agency are keen to establish how efficiently the pass/easement operates, as the principle could be adopted at other similar challenging sites. In order to get a comprehensive assessment, an exciting opportunity arose to work with Durham University who will use the project as part of a wider study looking at fish passage past human made barriers. That’s the good news. The bad news being that in order to be ready for the dace spawning season I was committed to delivering for three weeks through the bleak days of January and February. The summer would have been far too pleasant.

Due to the non-standard design the baffles were manufactured as a bespoke commission carried out by Northwood Forestry & Sawmills, made of oak as opposed to the standard recycled plastic. Once complete, myself and Norm spent the first week of the year huddled in his workshop drilling and bolting the stainless steel angle to each baffle which would enable them to be securely fixed to the concrete weir. All 36 pieces of the jigsaw were complete, coded and stacked in the lockup ready for installation.

049

In the workshop with Norm fixing the stainless steel angle to the baffles

050

Half of the baffles with angle attached and coded ready to go

The baffles would have to wait, as first we needed to help fish of the anguilliform variety, eels, to also be able to successfully navigate past the weir. With the eels having already made the 6000+km epic journey from the Sargasso Sea we were keen to ensure this weir would not be an abrupt dead-end. Although there was an eel pass on the weir, it has been largely ineffective for some time. A new and improved pass was called for, so out with the old and in with the new.

053

Out with the old…

062

and in with the new

With the eel pass installed, preparation to fix the baffles was underway. This primarily revolved around creating a dry working area, not necessarily an easy task when working in a river but with the temporary coffer dam supplied from RN Inspection Services this was achieved with unbelievable effectiveness.

073

The coffer dam installed providing a manageable working area behind

For the next two weeks, Roo and I lugged baffles, drilled holes, spaced, chocked, clamped, injected resin, removed then re-erected the dam and battled the elements. As the jigsaw slotted together the theoretical schematic drawing I was now well familiar with became a reality.

087

The baffles being clamped into position before the stud secured to the concrete with resin

090

Getting into the flow of things

133

Half way!

153

Time to move the dam and install the second half of the baffles

191

Finished! The notch bisecting the baffles to allow a deeper channel for fish to pass

Once complete, the time came to remove the dam and allow the water to flow over and through the baffles. With this action the Hogsmill became re-connected to the Thames once again.

The time lapse of the build conveniently summarises the full 3 weeks into 1 minute video can be seen here:

199

About to ‘pull’ the dam

211

Flow and fish passage returned to the channel

Over the coming year JBA (hydrology experts) will undertake a spot flow-gauging program, to ensure that the weir continues to gauge accurately with the modifications. Meanwhile Angus at Durham University and ourselves will monitor the LCB fish pass/easement aiming to understand its performance for coarse fishes such as chub, dace and roach.

184

One aspect of the monitoring is a camera looking across the upper notch

A BIG thanks to: All those involved in the various teams at the Environment Agency, partners in the project especially those in Hydrometry and Telemetry and Fisheries.  Angus, Martyn and Jeroen at Durham University for bringing their wealth of monitoring experience and expertise to the project. JBA for carrying out the hydraulic assessments associated with the project. Bedelsford School who kindly agreed to us hooking up to their electricity supply to power the monitoring equipment. Rob Waite at the Royal Borough of Kingston for helping us to secure access and parking at the site. The Thames Anglers Conservancy, especially Will, for getting involved and helping to install the eel pass. Norm Fairey for your continued help with all things fishy and manufacturing. And my good mate Roo for the long hours, hard graft, permanently cold hands and near permanent good humour.

 

Improvement Works on the River Dour

By Chris Gardner

In 2015 the South East Rivers Trust was awarded a £31k grant through the Department of Environment Food and Rural Affairs (DEFRA) Catchment Partnership Action Fund (CPAF) to deliver fish passage and habitat improvements on the River Dour in Dover. All these improvements would be designed to increase the health and resilience of the river environment for fish and other species, to meet the requirements of the EU Water Framework Directive.

River Dour an Urban Chalkstream

The River Dour is a short (4 km) little chalkstream that rises in a rural setting but soon flows through the highly urban centre of Dover. This delightful little river boasts a healthy brown trout population, but the habitat is highly degraded due to urbanisation and impounded / fragmented due to a legacy of watermills.

A spotty brown trout

We assessed the urban part of the catchment by walkover survey, looking for potential projects. These were then prioritised on a cost-benefit basis, resulting in four sites where fish and eel passage could be addressed. Two were simple fish and eel passage easements and two were sites for eel passes.

The ruins of the old water mill at Minnis Lane.

Work began in October 2015 with a volunteer event at Minnis Lane near the aptly named village of River. An old watermill ruin at the site presented a complete barrier to fish and eel passage. The main part of the weir was very high and a fish pass here would have been way beyond the budget available. However, a parallel channel had one small step weir and an over wide shallow section of channel upstream that made this route impassable. To make this passable to fish and eels, we fitted a wooden box to the downstream end of the small step weir had a wooden box, to raise the water level up the step so fish could navigate it. We also used faggot bundles as flow deflectors to define a deeper channel through the over wide shallow section. Many thanks to Anita for helping to organise the volunteers and to the volunteers for their hard work! You know who you are!

Fixing in the faggot budles at Minnis Lane

In May 2016, we also fitted two eel passes to Halfords Weir and Lorne Road weirs. These are large weir structures that will require technical fish passes in the future to make them passable to fish, but eel passes were achievable with the budget we had available. The Halfords weir site was quite straightforward – the setup of the weir allowed a simple gravity-fed pass to be fitted. Eel passes allow eels to move over weirs through a piece of conduit which contains brush bristles that provide a crawling medium. Water passes through the pass to provide attraction flow and passes are located at the edge of the weir as studies have shown that eels predominantly use river margins as migration corridors.

Untitled

The Lorne Road site was more complicated, because this eel pass needed to go up and over the weir, so a gravity-fed option wasn’t appropriate. Instead, we designed this pass to be fed with a water pump to provide attraction flow. Many thanks to Malcolm and Mick at the Lorne Road Mill building who allowed us to tap into their power supply! Also many thanks to Paul and Simon for their work building the passes – your help was very much appreciated.

2

We delivered the final aspect of the project later in spring 2016. Morrison’s weir (near Morrison’s supermarket) presented a barrier to juvenile life stages of trout and eel. To improve its pass-ability, the weir was notched in the middle to provide a streaming flow that fish can swim up, instead of a small drop and a thin plunging flow that fish can’t easily negotiate. Bristles were also fitted into the notch so eel could climb up.

3

Wise words from Baton Path Mural

Three Weirs: Part 3

Author: Nick Hale, Project Officer

Read Part 1 and Part 2 first!

And so 3 weirs fell!

Gatehouse, Weir 1

gatehouse-1

New Lodge, Weir 2

new-lodge-2

and Dairyhouse, Weir 3

dairyhouse-3

Watch the video of their removal here:

A total of approximately 250 tonnes of concrete and steel was removed from the river.

Removing the three weirs has unimpounded over 1 km of channel. By reconnecting these previously isolated sections of river, just over 3 km of this part of the Lesser Teise is now fully passable for fish!

Increased flow velocity and diversity has already seen the return of natural processes such as erosion and deposition. The mix of deeper and shallower areas will create a range of habitat niches for invertebrates and fish etc.

Directly upstream of the former weirs, the flows have begun to rework the river bed and gravel berms until its natural gradient is restored (as before the weirs were introduced). A previously drowned-out ‘in channel’ meander sequence has exposed gravel riffles, berms and mid channel bars.

These gravels will be continually reworked in a downstream direction, being replaced by new material from upstream. The well-oxygenated gravel riffles will become ideal spawning habitat for both salmonid and coarse fish like brown trout and chub.

A number fish were identified during the works with species including brown trout, minnow, bullhead, stone loach, gudgeon, dace, roach, perch, pike, brook lamprey and barbel.

This stretch of historically dredged river is typically characterised by steep/vertical banks with little or no marginal habitat. This project has exposed an abundance of berms and marginal features that given time will be transformed into a diverse marginal habitat.

Removing the weirs has eliminated the landowners’ responsibility for the upkeep of the structures and saved costs on the twice a year maintenance visits from the EA to maintain the signage and clear blockages in the channel.

What’s next?

We will be monitoring the river over the next few years to record how the project develops. It will be interesting to see how the higher flows over the winter months rework all the gravels.

In the spring we will sow some native marginal plant seed mix on the lower banks of our structures and take some more photos for the next blog.

A BIG thanks to must go to the landowners, Ian Johnstone and the Kent High Weald Partnership and the Environment Agency for all their help!

The Three Weirs: Part 2

Author: Nick Hale, Project Officer

Read Three Weirs part 1 here.

After many months of planning the project we were finally able to start the fun part and get on the riverbank!

The first job was to take delivery of all the machines and equipment such as the 15m long reach excavator and wheeled dumpers.  Access to the site was quite tricky but having a good delivery driver is always good!

1

Mike our excavator driver was raring to go but first we had to install our sediment control features, marker posts to measure changes in water levels/river bed level and also take a few photos for comparison.

It was great to finally get the breaker attached onto the machine and begin breaking out the concrete. The centre of the channel was broken up first, and then the sides.

2

breaking-out-concrete

The weirs were certainly well built! Sheet piling had been installed at the up/downstream ends of each weir to key it into the riverbed and act as the formwork when casting the concrete. Lots of 6mm steel rebar had been used to provide extra strength, and in some places the concrete was almost 1m thick.

Removal of the sheet pilling was quite a challenge at the first weir, with the downstream section being 1.8m in length.

Mike gradually broke up the weirs into manageable pieces, which were loaded into the wheeled dumpers and transported to the collection site. A local company was contracted to collect the waste material using grab lorries. Each weir was made up of about 80 tonnes of concrete which was about 5 grab lorry loads per weir.

concrete

Chestnut faggots were secured with chestnut posts (both locally sourced) to form the line of the new bank.

A marginal shelf of site-won soil was then encased in coir matting behind the faggots and secured to the banks with oak pegs. We will come back to plant these up in the spring.

10 14

With high spirits and with the weather thankfully on our side, we tracked up the bank to do battle with the next two weirs. Although the construction of each was similar, each site posed its own challenges. However one by one they fell, with all three weirs being removed and banks reinstated in a three week period, reinstating flows and passage for the first time in over half a century.

The benefits of the work were made clear before we had even pulled out of the site. We saw numerous fish passing the previous barrier to explore the stretch upstream.

Look out for our third and final blog on the Three Weirs Project to see some before and after photos and the timelapse video!

The Three Weirs: Part 1

Author: Nick Hale, Project Officer

An Environment Agency assessment of the Teise and Lesser Teise, two tributaries of the Medway in Kent, indicated there is a problem with wild fish stocks in the river.  Generally there is an absence and/or low abundance of key expected species such as brown trout, chub, predatory perch and pike, roach and stone loach.

In fact, the situation is probably even worse than this assessment indicates as a large proportion of the fish caught here are derived from artificial stocking, masking the figures of the wild population.

So what can be done about it?

One major contributing factor to these poor wild fish populations is the presence of barriers to fish migration: weirs. Weirs fragment the available habitat, prevent fish from reaching spawning grounds and change the geomorphology of the river channel as well. (For a reminder about the pros and cons of weirs, our very own Dr Chris Gardner wrote an excellent article recently on how weirs affect fish communities).

The Medway Catchment Partnership have been looking at barriers to fish migration in a bid to address this on a catchment scale. As a start, last year we successfully removed Harper’s Weir, restoring fish passage to a 3.5 km stretch of the River Teise. However, if you travel downstream, you are confronted by more and more weirs.

The Three Weirs Project looked to tackle a set of three weirs on the Lesser Teise, continuing this great work.

Where are the Three Weirs?

The Three Weirs, named Gatehouse (1), New Lodge (2) and Dairyhouse (3) are located on a 1.2 km stretch of the Lesser Teise near Chainhurst, Kent. All three are concrete weirs, likely originally installed in the mid-20th century for the purposes of agricultural land management.

weirs

What ecological benefits will result from removing the weirs?

The presence of a weir creates an impounding effect whereby the upstream water levels are much higher than normal.  This drowns out any natural features within the channel making it more like a canal than a river.

Impounded channel upstream of Dairyhouse Weir.

Impounded channel upstream of Dairyhouse Weir.

Removing the 3 weirs will increase the hydromorphological diversity (flow and river bed structure) of this stretch of river. Natural processes such as sediment transport and gravel mobilisation will return, exposing a range of original channel features like gravel berms and meanders. For example, the removal of Harpers Weir revealed 16 new riffles.

Ecological benefits will be seen both upstream and downstream of the existing weirs with salmonid and coarse fish being able to migrate through this previously unpassable stretch, improving their ability to carry out their full life cycle and ultimately increasing their chances of survival.

Localised improvements in water quality through faster, low flow conditions will reduce the build-up of ammonia and phosphates and increase dissolved oxygen to support a wider range of invertebrates. To capture these changes, an invertebrate survey has been undertaken by Robert Aquilina at specific locations along the proposed works area.  This process will be repeated in September 2017 to record any changes in diversity and abundance of the invertebrate community living within the channel.

In preparation for full removal, the wooden boards that were fixed to the crest of all 3 weirs were removed in 2015 with help of the Environment Agency. This reduced some of the impounding effect and allowed the channel upstream to adjust and stabilise prior to a complete removal of the structures in the future.

The next step now is to remove the weirs, but you’ll have to wait for part 2 to find out all about that!

Eel Passage on the Hogsmill

During the summer a collaborative project between Zoological Society of London (ZSL), Surrey Wildlife Trust Kingston Group and the South East Rivers Trust (SERT) was undertaken to improve elver and eel passage on one of the lower weirs of the Hogsmill, the Clattern Bridge weir.

The European eel is a critically endangered species and needs all the help we can give it.  Pollution, overfishing, global warming, disease and habitat loss have all contributed to the demise of this charismatic species. The eel has a fascinating and mysterious life cycle in which it starts life in the Sargasso sea as a larvae, migrates across the oceans via currents to European rivers, metamorphosing a couple of times on the way to become glass eels and then elvers.

Once in rivers, such as the Thames and the Hogsmill, they migrate upstream to find habitat in which to grow and develop into yellow eels. After 5-20 years of life in rivers like as the Hogsmill they metamorphose again into silver eels and travel back to the Sargasso Sea to complete their life cycle.  Weirs and habitat loss in our rivers are factors that cause issues for eels and stop their upstream migration to suitable habitat.

This project involved installing plastic tiles covered in regularly spaced plastic protrusions onto the weir face.  The weir at Clattern Bridge is smooth and has shallow fast water flowing over it.  The tiles allow eels to wriggle up the weir and into the river upstream enabling them to carry on their migration. Eels are not very good swimmers compared to other fish and prefer to ‘wriggle’ so increasing friction in this way is ideal for them!

Below is a great video of eels using a similar design on the Wandle:

Armed with a couple of battery drills, some long drill bits and various stainless steel fixings we attached a continuous line of tiles to the weir surface.

eels1

It was a lovely sunny day and perfect for a day in the river!

eel2

A big thanks to the Kingston local branch of SWT who provided funding for materials, drill bits and fixings and to ZSL for supplying manpower and eel tiles.

Elvers migrate upstream between April-September and so we are hoping they will appreciate our efforts when they arrive in 2017!

Author: Tim Longstaff

clattern-bridge-23-september-2016-3

Working on the Eden

In August 2016 we were contracted by Kent Wildlife Trust to install a backwater on the River Eden near Penshurst in Kent.

The river Eden is in the upper reaches of the Medway catchment and joins with the Upper Medway approximately 1 km downstream from Penshurst.

What is a backwater and why is it needed?

A backwater is an aquatic habitat connected to the main channel, sometimes only during higher water levels. Backwaters can be formed naturally as a river migrates across its floodplain, cutting off meanders.

Backwater habitats can be used on rivers that have been straightened or resectioned to increase the diversity of flow, habitat and ecology.

In this case we were asked to install a backwater that would provide two important functions for the river depending on the flow. In high flows, the backwater would become a refuge of slack water for adult fish to rest in until the normal flows return. In normal flows, the shallower water left in the backwater will warm up quicker than the main channel and act as a nursery area promoting the growth of young fish fry.

willows

Photo provided by Kent Wildlife Trust of project area last Winter 2015

What we did

The project got off to a quick start with local tree surgeon Ivan Carson, from Penshurst Tree Surgery, making short work of the 3 cricket bat willows.

These willows were coppiced to near ground level to allow more sunlight to reach the backwater – helping to raise water temperature during normal flows. A bonus benefit of this tree removal is a reduction in the amount of leaf litter entering the backwater, reducing future maintenance.

With a tight schedule, work on the backwater commenced. First the old fence was removed and the topsoil was stripped back.

Our expert excavator, Jimmy, started shaping the backwater entrance. All the spoil we removed was tracked to the far end of the landowner’s orchard to improve their existing track.

Everything seemed to be going smoothly until Jimmy’s bucket hit something solid! This turned out to be a huge tree trunk of approx 1 m diameter running parallel to the river, across the backwater entrance.

digger-and-trunk

trunk

With no idea how long the trunk might be, we decided to remove the central section. Most of it was actually below water level, which meant our saw wasn’t quite up to the job. Fortunately, Ivan kindly lent us one of his and the obstacle was overcome by our very own Toby.

The silver lining of this small delay was that we didn’t need to install any large woody as cover for fish.  We even spotted a Perch of approx. 1.5 lbs sunning itself in the shallows until it was spooked, and darted underneath one of the remaining stumps – woody cover in action!

Whilst Jimmy was finishing off the backwater, Toby and Alex started to install the new fencing around the backwater. This fencing will exclude cattle from the backwater, preventing over-grazing and reducing bank erosion.

fencing

With the backwater construction complete, it was time to add the plants. Marginal plant plugs were added around the backwater, and wild flower seed was scattered on the ground to provide some ground cover before winter.

clearing-up

The landowner seemed really happy with the final result – especially once he saw all the marginal plants.

The project took 6 days to complete and we look forward to seeing how the backwater matures overtime.  Lots of fish fry were spotted on our most recent site visit which suggests we did a good job!

dsc_0011

Water quality improvements are on par at Richmond Park

Shortly I will post another blog updating you on how the river improvement works in Richmond Park are settling in one year after they were completed. Although the river habitat works have been completed (for now!) work has by no means ended. In addition to improving the habitat, our attention is also focused on addressing the poor water quality entering into the Brook.

Upstream of the Richmond Park golf course, rain water pours off the surrounding urban catchment and notably down the incredibly busy and often choked A3 at Roehampton Hill. It then flows down the gulley pots, into a surface water drain before this opens out into a ditch which flows across Richmond Park Golf Course before discharging into the Beverley Brook. Such road runoff is known to cause detrimental effects to the aquatic environment, not only from the significant quantities of sediment carried in it, but additionally from the contaminants bound to it. These include Poly Aromatic Hydrocarbons (PAHs), hydrocarbons and heavy metals. Our aim was to therefore capture the sediment and the contaminants before they reach the Brook. This was achieved with a two pronged attack.

img_2820

Oil from the A3 covering the surface of the pond in the golf course. Thick black sediment covers the bed

First of all, mid-fairway at the upstream end of the golf course we opened the ditch out to create an on-line pond, known to us as a silt trap but to golfers as a feature water hazard. With help from Rob McInnes, the pond’s size was calculated so that all coarse sediment down to 0.1mm would drop out as a consequence of lowering the velocity of the flow. A shallow marginal ledge was incorporated along the length of the pond, which has been planted with a mix of wetland plant species to promote deposition, whilst providing species and habitat diversity. By emptying the pond regularly, the silt is removed from the system and the effectiveness of the trap is maintained.

imag1125

Starting to open the ditch out

img_3254

A few months after completion, the pond is trapping plenty of silt (and plenty of golf balls)

The second measure took place a few hundred metres further down the ditch where an existing online pond, in the shape of a ring doughnut, provided an excellent opportunity to be modified to create a wetland. The plan was to re-jig it so that the doughnut became a U-shape. This prevents short-circuiting, therefore increasing retention times, reducing velocities and again promoting a depositional environment.

img_1947

The pond before works start

The pond was too deep to plant straight into, so we needed to find spoil to fill it in. What better way to produce the spoil than dig a second wetland immediately upstream of the first, which will increase the treatment capacity further.

imag1167

Re configuring and filling in of the pond

Six thousand plants consisting of over 20 species were planted in the wetlands. The dense structure created by the plants results in even finer sediments being captured than in the silt trap upstream.

img_3226

The wetlands newly planted with 6000 plugs and fenced off

img_3260

August and the plants have established

Furthermore, this has now created a fantastic wetland habitat full of dragonflies, damselflies and frogs to name a few. Both the silt trap and wetlands have been fenced off and have bird twine strung over them to prevent the large population of geese from nobbling the plants before they had the chance to establish. The total area of both is approximately 800 metres square.

A simple water level control structure was created at the outlet of each wetland. As sediment accumulates and reduces the depth of water over time, another drop board can be put in, allowing the water depth to be increased, therefore reducing maintenance requirements and prolonging the life of the wetland.

The effectiveness of the installed measures is currently being monitored, however a coincidental site visit during a pollution event helped to anecdotally demonstrate the effectiveness. Run-off from a presumed building site was bringing significant quantities of sand rich water into the ditch. After the silt trap, the turbidity of water flowing out was visually improved. Walking further down the ditch network, after flowing through both wetlands, we were incredibly impressed to see that the water flowing out and into the river was clear to the eye. Although this was always the theory behind why we created these features, to see it work first hand to such a great effect was brilliant and hugely satisfying. With contaminants generally being bound to sediment, this clearly demonstrates not only a reduction of sediment input to the river but indirectly of contaminants too.

silt-trap

Thick sandy water flowing into the sediment trap

downstream-of-wetlands

Water in the ditch downstream of the sediment trap and both wetlands

outfall-into-river

Significantly improved water clarity entering into the Beverley Brook

Job done!! (for now anyway). I am now working up the next phase of water quality improvements. Updates will follow shortly.

As always, the success of this project is down to the valuable contribution of many people and organisations.

Big thanks to the ongoing project partners; the Environment Agency, Defra, The Royal Parks and Friends of Richmond Park. Thanks to Jon Dummett and Gary Stewart at Glendale Golf Course for surprisingly being so willing in allowing us to dig up their course and for their continued support since. Thanks to Rob McInnes at RM Wetlands & Environment Ltd for guiding the designs, Ben and the guys at Aquamaintain for braving the cold February days delivering the work and again for planting it up. Thanks to Thames Water for providing the flow meter which was installed in the ditch network to inform the design and finally, to Layla at Queen Mary University for monitoring the work.

Restoring the Hogsmill with Volunteers

A lot of our projects recently have been large scale – removing weirs, installing fish easement solutions and reprofiling large sections of river. But now it was time for the real professionals to step in…

Volunteers

For one week in March, Toby and I were in chest waders in the Hogsmill in Ewell. Over 5 days, we were joined by volunteers from the Lower Mole Project and other local volunteers from the Hogsmill Pollution Patrol and the Wandle – all trying river restoration first hand.

The River Hogsmill is a chalk stream in south London where we’ve been working to increase habitat connectivity over the last few years. Toby has been busy removing weirs where possible, or installing rock ramps to make them passable to fish.

In Ewell, Toby removed 3 small weirs to open up fish passage throughout this 1.6 km stretch. What was missing was fish habitat.

So what did we do?

The Hogsmill through the Open Space is artificially straightened and canalised with wooden toeboarding. There is little habitat variation in channel with slow moving water and a silty bed.

Straight Channel

On the first day, a team of volunteers got stuck in pulling out the large railway sleepers serving as toe boarding. Over the next four days, a total of 48 sleepers were removed – the first step in naturalising the bank for 1km through the park.

Sleepers

Meanwhile, carefully-selected trees were felled to increase light reaching the river. With this material, we started to create brash berms to narrow the channel and increase flow.

A holding log was placed at the downstream end of the berm and secured in place with posts and wires. Then brash from the surrounding areas was added to build up a berm.

Holding Log

This was all secured in place with chestnut posts and wire across the brash after some technical “squishing”…

Squishing

Over the next four days, the volunteers created a further 8 berms. You can see from the photos that the river began to respond instantly. Flows were increased where the channel was narrowed and scoured pools started to form.

On the last day we moved our attention further downstream to the site of a weir removal in 2014. Here a small weir and concrete abutment walls were reduced, but due to the close proximity of the path had to leave a semi-engineered bank.

To enhance this, pre-planted coir rolls were fixed along the bank to soften this edge and create a more natural marginal habitat.

Coir Rolls

To install these though was no simple task. They were secured in place with chestnut stakes and wire thread round the posts and through the mesh of the bank line. Believe me, that was a skill in itself…

Wiring Coir Rolls

Here are some photos of what we all achieved..

Finished!

Big thanks to everyone who came along!! We’d also like to thank Epsom & Ewell Borough Council and the Lower Mole Project.

Rustling up some Riffles

Our Project Officer Rosie has been out on the River Teise undertaking her first weir removal.

Why was this weir an issue?

Harpers Weir formed an impassable barrier to fish passage on the Teise, a tributary of the River Medway in Kent.

Harpers Weir

Weirs such as this impede the movement of fish upstream and downstream, preventing access to other habitats required for a healthy lifecycle.

They also impound the river upstream, slowing the flow of water and resulting in the deposition of silt on the channel bed. In the case of Harpers Weir, this impoundment was observed for several hundred metres upstream.

Impoundment

For all these reasons, we’ve been very keen to remove the weir and restore fish passage to this section.

In 2015, Rosie started the process by removing the wooden boards on top of the weir, reducing the height to see how the river would respond. You can read this blog here, but in summary it was looking good!

Then, in February this year, Rosie and our contractors Amenity Water Management arrived on site to start the full weir removal.

The concrete weir and flanks were broken up using a hydraulic breaker attachment, before being removed with an excavator. The concrete underneath the footbridge immediately upstream was also removed to let the river bed naturally re-grade back upstream (the footings would otherwise create a new barrier after weir removal).

Diggers on Site

Once the weir and bridge footings were removed, the banks where the weir once stood were regraded, using the excavator with a bucket attachment.  The toe of the banks was stabilised using coir geotextile to line the banks secured with wooden pegs, which in turn were held in place with faggots and pinned with untreated chestnut posts secured with high tensile fencing wire.

After Weir Removal

Once this weir was removed, the upstream impoundment disappeared, and a total of 16 new riffles emerged, with pools between them – all great habitat for many species of bugs, fish and water birds!

You can watch the whole project in our time-lapse footage below!

This project was funded through Defra’s Catchment Partnership Action Fund awarded to the Medway Catchment Partnership, focusing on the River Teise within the Medway Management Catchment.

Calling Hogsmill Volunteers!

Thursday 17th, Friday 18th & Saturday 19th March
10am – 4pm
Hogsmill Open Nature Reserve

This March, the South East Rivers Trust are delivering some restoration works on the Hogsmill through the Hogsmill Open Nature Reserve, and we are looking for volunteers to join us.

What will we be doing? 

We are going to be implementing some restoration through a 1 km stretch of the Hogsmill, such as installing Large Woody Material, bank softening and channel narrowing. These techniques will help increase flow diversity in the river, creating habitats for invertebrates, fish and other wildlife.

Make sure you sign up!
For each day, we are looking for a maximum of 15 volunteers to join us. So if you are interested in joining one or all days, please email Polly as soon as you can to book your place at volunteering@southeastriverstrust.org.

Once your place is confirmed, we will send round more details nearer the time on where to meet us, timings and what you need to bring.

IMG_1356

Tree Planting in Richmond Park

I am sure you have all been following the progress in Richmond Park with our Beverley Brook Restoration Project. Well now that the main channels works have been completed, we were ready to move on to the next stage: tree planting.

Tree Planting

Adding the right number of trees along the channel is crucial to restoring the habitat. Trees provide excellent cover for fish from predation, the shade they create helps to keep the river cool in the summer months, they provide habitat for birds and insects and the seeds as a food source. However too much shade can prevent marginal, emergent and submerged plant growth, so a balance has to be struck.

On a sunny February morning we were joined by seven volunteers from Friends of Richmond Park to plant nearly 200 trees along the two restored sections on the Beverley Brook.

To ensure we got it right, Toby (Senior Projects Officer at SERT) had worked closely with Royal Parks’ Julia (Head of Ecology) to map out where each species should be planted and how many.

More Trees

Tree species planted included several types of willow (white, grey, osier and goat) as well as alder, black poplar, blackthorn, hawthorn, hazel, birch and elm. All trees were given a protection from grazing and from high flows to give them the best chance at establishing. Given the flashy nature of the Beverley Brook, those trees planted closer to the channel were given some extra protection from strong flows with a large stake providing cover.

More trees

Next on the agenda for this project is to add plants to the marginal habitats in April. Watch this space and come and get involved!

Big thank you to our volunteers from Friends of Richmond Park: Brian, Ian, Janet, Jed, Mike, Roger and Simon.

Lovely gravels

Restoration to the Beverley Brook in Richmond Park (Phase 1)

The write up of the introduction to the project can be viewed here.

I have now returned from being out at Richmond Park delivering the first phase of restoration to the Beverley Brook in Richmond Park. It has been a while and lots has happened which I am keen to share. I suggest you make a cuppa, take a seat and get comfy.

The Beverley Brook possesses incredibly flashy characteristics due to the urban nature of the river with a significant proportion of the catchment being coated in hard, impermeable paving. With the plan to be on-site for seven weeks through the British autumn undertaking a significant amount of in-channel works to 600 m of river, we were firmly in the hands of the weather once again.

The aim of the project is to enhance the heavily degraded, uniform and generally inhospitable channel so that it would be more inviting to the native fauna and flora that should be present and abundant.

A sorry state at the start of the project

A sorry state at the start of the project

Before the works started we undertook a range of monitoring to capture the baseline condition of the river. These will be vital and incredibly interesting to refer to in the years to come to demonstrate the effectiveness of the project. The monitoring included a two day fish survey undertaken by the Environment Agency, habitat mapping, aquatic invertebrate and plant surveys, sediment analysis and novelly for us, a drone recorded aerial video and photography of the site with some exciting low fly-over manoeuvres.

Drone in Action

Drone action

The work then commenced. With the help from the Aquamaintain guys once again and with Trevor behind the controls of the long reach excavator, we set about spicing up the bland channel. The key to this was variety. A variety of flow types, a variety of channel widths, depths and bank profiles. By adding diversity, a mosaic of habits would be created, providing for  a range of species throughout their life stages.

When discussions about the project first started with the Royal Parks a year or so ago, I could not believe my ears when they announced that there was no shortage of trees and rootwads we could source from the Park to use in the river. With this rare offer, I was like a kid in a sweet shop. With the help of Mick Baker, the Park’s go to forester, dozens and dozens of oak trees were felled (I must add this is as part of the Park’s management regime), the root balls dug up and all carried down to the river by the mighty forwarder (tractor).

Rootwads and LWM ready to be used

Rootwads and LWM ready to be used

Some of the LWM stockpile seen from the air

Some of the LWM stockpile seen from the air

Mick bringing down another load of oak tree tops

Mick bringing down another load of oak tree tops

The wood was introduced to the river in a variety of methods to perform a number of tasks. In places, masses of the tree tops and smaller limbs were stacked up against the bank extending between a third to half way across the channel. These were compacted with the huge force of the excavator and then secured with posts and fencing wire. This technique reduces the channel width to give the river more energy whilst providing complex habitat both above and below the water line. Furthermore, the dense network of branches creates slack water, encouraging silt to drop out whilst also capturing leaves and seeds. Overtime, these structures will consolidate and vegetate to form a new bank. By alternating the bank these are constructed on, a meandering sequence is created in conjunction with the next method, backfilled faggots.

Tree tops and brash in the foreground before being compressed and secured

Tree tops and brash in the foreground before being compressed and secured

Faggots (brash bundles) are fixed to the bed with posts and wire to create the new bank line, again reducing the channel width in places from 7 metres down to 2.5. The steep banks are then regraded and the spoil placed behind the faggots to produce low lying berms which in time will become wetlands when marginal plants establish.

Faggots with incorporated LWM being used to narrow the over-wide channel

Faggots with incorporated LWM being used to narrow the over-wide channel before being backfilled with the regraded banks

Protruding out of the tree tops and faggot berms, larger tree trunks, rootwads and multi-limbs (Large Woody Material, LWM) where fixed into place, extending out across the channel.

Rootwads providing complex cover

Rootwads providing complex cover with a backfilled faggot berm behind

Doing so is a great way to not only provide complex cover but is also a way to reinstate energy back to the river. As water rushes over, under and past the structures, the bed is scoured, creating deeper holes and throwing up the cleaned gravels into shoals and bars. This is a truly rewarding aspect of the work, identifying where and how to place the wood. Even under low flows, the impact can be felt immediately with the gravels being kicked up around your feet. A day later, the bed downstream is glowing with gravels as opposed to the previous uniform blanket covering of sand. And again, after higher flows, features are carved out and created.

LWM immediatley forming holes, shoals and riffles

LWM immediatley forming holes, shoals and riffles

The banks were also naturalised as we progressed downstream. The steep gradient was reduced where possible to provide transitional areas between the terrestrial and aquatic habitats. Intermittently, hugely over-engineered concrete headwalls with tiny two inch blocked land drains poking out scared the bank. Being redundant, these were removed with a total of 20 tonnes of concrete being mucked-away from site.

Another concrete headwall being removed

Another concrete headwall being removed

Significant regrading of the perched banks to form a wide wetland area on an inside meander, soon to be planted

Significant regrading of the perched banks to form a wide wetland area on an inside meander, soon to be planted

A key aspect of the project is to restrict deer access to the channel. To do this the entire 600m length which is divided into two sections was fenced off. However, to prevent them accessing the stretches by simply walking up the channel, we had to construct river gates at the ends of the sections. In a river as deeply incised and flashy as the Beverley Brook is here, this took some doing. We ordered in several chunky telegraph poles. Some were cut and notched to form half jointed A-frames. These were positioned in deep holes high up on the banks. Mounted onto these, the excavator lifted 12 metre telegraph poles to span the channel. From these using stainless steel eye bolts and chains, oak gates from wood sourced and milled in the Park and manufactured by our good friend, Norm Fairey were hung. The principle being that the river gates prevent deer passing but importantly not causing a debris build up.

A section of the 600m of fencing which has been erected

A section of the 600m of fencing which has been erected

The moment of truth, the telegraph pole spans the 12m gap before the braces are removed from the A-frames and the holes are filled with concrete

The moment of truth, the telegraph pole spans the 12m gap before the braces are removed from the A-frames and the holes are filled with concrete

Jack standing back and admiring one of the three telegraph pole river gates completed

Jack standing back and admiring one of the three telegraph pole river gates completed

A conveniently placed bridge provides the structure for the fourth set of gates

A conveniently placed bridge provides the structure for the fourth set of gates

The last task was to create a deer and dog access point. These access points prevent the banks being eroded (poached) with the subsequent input of sediment to the channel. The banks were regraded to a shallower angle and first armoured with 20 tonnes of gabion stone and then covered with compacted scalpings.

Access point in the foreground with the most downstream river gates behind marking the end of the restored section or river

Access point in the foreground with the most downstream river gates behind marking the end of the restored section or river

As I mentioned at the beginning, we were needing the autumn weather to be kind to us. Who could believe it? Throughout the first three and a half weeks we barely had a drop, allowing great progress with the in-channel works and with ground conditions holding up well. After that, we did lose a couple of days due to rain and the spatey flows but I considered we had been lucky and gratefully accepted it.

The New Year has provided the first heavy flows. I managed to get down to the river yesterday and waded the length inspecting how things are bedding in.  I am pleased to say that the restoration has certainly been successful in the aim of providing variety. With more energy, the river at last has active functioning processes.

Before, blandness!

Before, blandness!

And after, variety is the spice of life!

And after, variety is the spice of life!

The Large Woody Material is scouring holes with loose gravel riffles forming downstream. The bed on outside of the meanders is deepening with large deposits of sediment forming shallow berms on the inside. The tree tops are accumulating sediment and consolidating quickly. The water’s surface is rippled and broken making the river audible once again. Even whilst doing the work, each morning a walk up the river demonstrated the immediate effectiveness with dace and chub taking up residence in new lies and pools where before there were none. I am thoroughly looking forward to seeing how the river adjusts and naturalises over the coming weeks, months and years.

So moving on, next month we start addressing diffuse urban pollution entering into the Brook from the A3 by digging a sediment trap and creating two wetlands. We are also having our first of several planting days. This one introducing trees to the river banks to provide shade and Large Woody Material in the future. We will keep you posted.

There are so many people to thank. The funders; The Friends of Richmond Park, The Royal Parks, the Environment Agency and the Beverley Brook Catchment Partnership. And those that helped out;  Simon, Julia and Adam at The Royal Parks, the guys at Aquamaintain; Ben, Dave, Jack, Zac, Lloyd and Roo. Trevor from Land & Water  in the machine, Norm Fairey, Curling Fencing Contractors, Mick Baker, Andy Birnie, Colin Hampton, Luke and his drone, the list goes on. Thank you all.

 

Fish Passage on the Cuckmere

We have been working in partnership with the Cuckmere and Pevensey Levels Partnership to deliver a fish passage project at Sessingham Weir on the Cuckmere.

The weir currently causes an impassable barrier to fish, preventing them from accessing all the habitat required for a healthy lifecycle. This in turn can make fish less resilient to other pressures such as pollution and climate change.

Many fish species thought of as being non-migratory will in fact, given the opportunity, make substantial movements within a river system, particularly to find good spawning habitat. In unobstructed rivers, species such as roach may move 10’s of kilometers. By making the weir passable to fish, we will reconnect approximately 6.2 km of valuable habitat upstream and downstream.

Unfortunately due to the presence of a water pipe running underneath the weir it cannot be fully removed. In September we permanently lowered the weir blade and have already seen some fantastic habitat improvements such as increased flow diversity.

Before and After at Sessingham Weir

We are now planning to remove the redundant weir gate and are designing a solution to make the weir passable to fish.

Action on the River Teise!

We’ve started our project on the River Teise to make a weir passable for fish migration.

Weirs were introduced years ago to help control the flow of water, allowing our ancestors to operate mills. Nowadays many remain in rivers despite no longer being required.

Weirs are a barrier to fish passage and leave the habitat fragmented with fish populations isolated. In the event of pollution or other presures like climate change, these isolated populations are at greater risk with nowhere to escape to.

Although being a barrier to fish migration is a significant problem, weirs also interrupt the natural flow of rivers, resulting in a degradation of habitat. Upstream of weirs, water is slowed down which causes silt to drop out and accumulate in the channel.

This image from the Wild Trout Trust explains the effects of weirs on fish habitat:

WTT Weir

Funded through Defra’s Catchment Partnership Action Fund, we’ve started works on a weir on the River Teise – where Olly and Rosie carefully removed a number of boards from the top of the weir.

Weir Board Removal

After removing the boards, the impounded water levels upstream dropped noticeably, revealing many natural features of the river which had been drowned out when the weir was put in place.

Before

Before

AfterAfter

New Habitats

Some of the diverse new habitat revealed by lower water levels above the weir

The next phase of the project is to remove the impoundment and enable full fish passage and habitat restoration, so watch this space!

Delivery on the Dour

Last month, we ventured all the way to Dover to start delivery of our River Dour Restoration Project.

The Dour is a short river, roughly 4 km in length, which runs into the sea at Dover Harbour.

We were addressing fish passage at a weir near Kearsney Abbey at Minnis Lane. Here the Dour runs through a ruined building, causing blockages to fish passage with the presence of several small weirs. The river itself has started to create its own bypass channel and our aim was to enhance this channel to allow fish passage upstream of the site.

Minnis Lane Site

Installing Brash BundlesTo do this, we installed brash deflectors to concentrate the flow of water to a narrower section, ensuring there was enough flow for fish to swim up without becoming stranded.

We were joined by 6 local volunteers on the day to help us install 12 brash deflectors in the stream.

Each deflector was secured in place with hazel posts and wire to ensure they stayed in place in higher flows.

By placing the deflectors so that they’re pointing upstream, we directed the flow of water into the middle of the channel, creating a deeper section for fish and eels to swim up.

We will be back to finish the site off soon and see how our deflectors are working.

Many thanks to our volunteers who helped on the day: Bethany, Katharine, Lilian, Ray, Simon and Tom. And a big thank you to the local Scout Club for letting us park our van in their carpark.

So before….

Before 1Before..

Before 2

After!

After 1

After..

After 2

The Catchment Based Approach in action: Natural flood risk management in Stroud

When it comes to protecting communities from the worst impacts of natural disasters like the recent floods in Cumbria, York and Manchester, it’s easy to feel a little helpless in the face of global-scale influences like El Nino and the possible effects of climate change.

But as one of the warmest and wettest Decembers on record spills over into a grey and soggy January, and flood risk management continues to dominate the national conversation, here’s a fascinating case study that shows how local communities can use the Catchment Based Approach to make a real difference in their local area.

This video from Stroud District Council shows how residents are working with landowners further up the Frome catchment to slow the flow of heavy rainfall down these steep valleys, using natural materials to hold flood water back in the hills and preventing it from hitting vulnerable urban pinch-points all at once.

It’s a lot less expensive than many other heavy-engineering-and-dredging solutions to flood defence. And, as part of a community and catchment approach, it looks much more likely to succeed and be sustainable in the long term too…

Welcome to Chris: Our Catchment Manager

ChrisWe are pleased to welcome a new member of Staff to the South East Rivers Trust: Chris Gardner, our new Catchment Manager.

Chris has joined us with 17 years of experience as a fisheries scientist in both the public and private sectors. He has also led on a number of peer reviewed papers on fish migrations ranging from coarse fish in large lowland rivers to salmonids (trout and salmon) in chalk streams like the Wandle.

Chris will be helping us deliver the Catchment Based Approach across our area in the south east, working closely with our partners to deliver ecological benefits to our rivers and their catchments.

“I’m really looking forward to working in the third sector, delivering real improvements on the ground and monitoring the success of river rehabilitation by demonstrating the ecological response to such interventions.”

So welcome Chris!