Tag Archives: River restoration

Hackbridge river restoration – the work progresses.

The river has continued to change quickly as our skilled contractors from Cain Bioengineering bring to fruition our plans. Nick, Jimmy, Alex, Will and James (with the occasional visit from Pete) have been working hard to continue the bank formation, backwater creation and island regrading with diggers, faggot bundles, stone, gravel and a lot of hard work.

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The Cain Bioengineering crew hard at work:

This has resulted in a narrowing of the low flow channel and increased flows instream.  The narrowing and meandering river channel brings a lovely diversity of flow to the river which is important to give different habitats for different species of fish, plant and invertebrate life.

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Increased flow diversity brings increased habitats:

As the work progressed the rivers natural gravels were revealed by the increased energy of the water and the working of the bed.  the gravels vary in size from very small to ‘cow skull’ size pieces of flint.  It is amazing to think that many of these gravels have probably not seen the light of day for hundreds of years!

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Natural Wandle gravels:

A causeway has been  built which creates a separation of the river from the backwater pond area.  A bed of stone was laid onto which coir geotextile (appropriate considering how many coconuts we find in the river!) was laid. Gravel was used to weight the coir down and then silt and sediment from the pond area was laid over this and the coir folded and sown shut to create, in essence,  a large sausage like growbag!

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The making of a causeway:

More silt and sediment was then overlaid ready for planting up with marginal plants.

The electricity cables were eventually spiked and cut to prove that they were indeed abandoned and this then allowed work to commence on the removal of the 3rd weir below the footbridge.

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Proving the electricity cables are dead so we can excavate the bed:

The breaker soon made short work of the concrete and brick structure and the river was free of its last obstruction (around Culvers Island that is!). Soil from the island and sediment removed from the backwater pond area was placed onto the new banks ready for our planting events on 6,7 and 8th September.  There is still space to attend if you would like to. Contact Erica Evans at Erica.Evans@wandletrust.org to sign up.

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The third weir bites the dust:

Many passersby have commented on how clean the river now looks as the silt has been shifted and the clean gravels are seen. The increased water flow and movement is important in increasing oxygen levels in the water too. The Heron loves the work and has been seen at all times of day feasting on the thousands of tiny fish in the area.

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The heron enjoys it’s rich feeding grounds:

The Contractor’s work will soon be finished – watch this space for a final update!

Then it is onto the planting and hopefully good growing conditions this autumns!

Hackbridge river restoration project underway!

After months of planning and preparation the weir removal and river restoration project at Hackbridge is finally underway!

Those of you who have crossed the road bridge over the river or walked along the Wandle Trail in the past few weeks will have seen big changes with heavy machinery in the river, the sound of breaking concrete and the sight of a river re-emerging.

Our skilled contractors Cain Bioengineering with site manager Nick and his team of Alex and Jimmy have been working hard to bring to reality our vision for the river.

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Gravel, stakes and hazel faggot bundles at the ready in the compound:

The work started with the removal of the heavily creosoted toeboarding from around the edge of the island.

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Toeboarding removed from the island and an old speaker found in the river!:

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The toeboarding still smelt strongly of creosote after many years in the riverbank:

A new island bank line was then created with hazel faggot bundles secured with chestnut stakes and backed with coir netting in order to extend the island and narrow the river.  Sediment from the channel (of which there was a lot!) was then placed behind the new bank line.  This sediment is a result of the weirs slowing the water flow and causing sediment particles to settle out and smother the natural gravel bed.

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Scraping sediment to place behind the new bank line:

After the creation of a new bank line parts of the island were regraded to create a gradually sloped bank that will be planted up at a later date with plants suitable for the different habitat zones created. The dead trees were retained as they are an important habitat for all sorts of creatures including bats, woodpeckers and invertebrates.

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Regrading the island with the excavator:

With the bed nearest the weir cleared of much of the sediment the weirs were breached and the process of breaking up the old weir structures begun.  The weir was found to be made up of cast iron plates, concrete, brick and lumps of chalk.  The cast iron was recycled and the proceeds will be converted into a pair of waders for our volunteer events!

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Smashing up the old weir:

Once the weirs were breached the water levels dropped upstream and the process of narrowing the channel was started with a combination of more posts and faggot bundles or stone.

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Forming a new bank line to narrow the river:

A sinuous meandering channel is starting to take shape and will allow for a variety of depths and flows with deeper faster flowing outside bends and shallower slower flowing inside bends providing varied habitats.

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Starting to take shape:

There have been many practical challenges along the way with sewer pipes, water mains and electricity cables criss crossing the river to be identified and avoided.  The joys of urban river restoration projects!

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Locating an electricity cable:

Look out for more updates as the work takes shape over the next week!

We will be holding a number of planting events to plant the island with native plant species in early September so please get in touch if you are interested in getting involved.

Pollution alert: Storm flows from Caterham Bourne through Beddington sewage treatment works

Following our recent report that record rainfall this winter has resulted in the reappearance of the Caterham Bourne, we’ve just received this information from the Environment Agency:

Because of the high ground water from the Caterham Bourne, ground water is being pumped into the foul sewer to relieve flooding issues in the Kenley and Purley area.  This is also to protect Sutton and East Surrey’s potable water treatment works at Kenley.

Because of this there has been an increase in water flowing into Beddington Sewage Treatment Works and the Works are running under storm conditions. This means that the water coming from the works is a mixture of final treated sewage and storm water.
This has been going on for a few days now and could last for a while. However, several partner organisations including the EA, Thames Water, local Councils, the Police and Fire Brigade are working to manage the situation as immediately and effectively as possible.

Needless to say, we are taking this situation very seriously, and will post updates here as we receive them.

Update 1 (2.30pm, Monday 24th Feb): the EA have informed us that “free ammonia” NH3 levels are currently very low in the lower river, and no environmental damage has been detected so far.  However, sludge which has been scoured from Beddington’s storm tanks may be getting into the river, and may look like shredded toilet paper or similar.

Update 2 (12pm, Tuesday 25th Feb): There is sewage debris, sludge and fungus being seen all along the river downstream of the effluent channel to at least Penwith Road.  Water is not being pumped to the foul sewer now but the amount of water entering the sewage treatment works is still high and is therefore still operating  under storm conditions.   Dissolved oxygen levels are low but not thought to be a cause for concern yet.

If you’re out on the river and notice offensive smells, unusual quantities of sanitary products, or fish or other wildlife in distress below Beddington STW, please phone them in to the usual EA hotline: 0800 80 70 60. Thank you!

Launching our new South East Rivers Trust website

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As part of expanding our charitable area of benefit to cover several other rivers across south east England, as the South East Rivers Trust, we’ve just launched a new website to represent this area of our activity.

Southeastriverstrust.org will feature details of all our future work on the Hogsmill, Beverley Brook and other rivers.

If you live anywhere in the south eastern area, and would like to get involved in our partnership work on the Beverley Brook, Darent, Dour, Hogsmill, Medway, Mole, Eastern Rother or Stour, please let us know!

The Wandle makes headlines in The Angler

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There’s a great article about the Wandle river restoration story in the latest issue of The Angler, the Angling Trust’s new-look magazine, which has been dropping through members’ letter boxes over the weekend.

The Angling Trust was instrumental in helping the Wandle Trust to negotiate the 5-year Living Wandle project funding for the river’s restoration, after the notorious pollution incident in 2007, and its Fish Legal team are constantly negotiating and fighting court cases on behalf of other rivers and their local residents.

If you’re already a member of the Angling Trust, keep an eye out for the article. And if you’re not a member, but you enjoy fishing the Wandle and other rivers, we highly recommend joining the Trust and supporting one of the great forces for good in the conservation world!

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The Angler - Wandle 2-001

Hogsmill weirs: The two off Old Malden Road (part 2)

That’s another two obstructions ticked off the Hogsmill list with fish passage successfully being restored to this stretch of the river. Since the last blog, when the downstream weir was in the process of being removed, things have moved on dramatically. Before I explain what has been done, first a quick good news story. At the top of the stretch a surface water outfall discharges into the river next to the bridge footing. Every day, large quantities of fat and food matter were entering into the river from this due to a clearly misconnected pipe up the system. You can see the severity of this from the photo, although without scratch and sniff you will have to take our word on the pungent aroma. I reported this to our local Environment Agency Pollution  Officer and in double quick time they had been out to site and identified the source as being the kitchen sinks in the pub over the road. The pub was unaware of the misconnection and has agreed to rectify the issue by connecting the sinks into the foul sewer and not the grey water. Misconnections are a big problem and cause poor water quality in urban rivers. Click here for help to identify if your house is misconnected.

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Misconnected outfall, covered in fat with food accumulated at the bottom

Back to the main works, with the weir gone, the impounded water drained away revealing the river bed that lay beneath the deep, dark and sluggish water for so many decades. What became immediately clear was the impact that excessive historical dredging has had on the river. The true scale of the river at this point was made apparent. The facade of being a large, deep river was lifted and the reality of the stream which the Hogsmill really is at this point in its journey unveiled. A river, no more than a metre wide snaked its way in the bottom of the 10 metre wide channel. Admittedly the chalk fed source of the river 3.5km upstream will be running low at this time of year but the river looked markedly out of place in the over-sized channel.

The true river revealed

The true river revealed

Nine rows of chestnut posts were driven in, crossing the channel in shallow curves at regular(ish) intervals down the 90m stretch of river. In total 700 posts were used as I am sure the guys on site will testify to. The introduction of gravel then commenced. Large flints were hand placed behind the posts to prevent washout and maintain the head across each pool. As the deliveries of gravel came in, quantities of these large flints were irregular and lacking. A decision was made to substitute these for more uniform, larger gabion stones which would assure the longevity of the structures. This was also banked up at the outside edge of each line of posts to prevent the river from eroding the banks.

The gabion stone is stacked behind the posts

The gabion stone is stacked behind the posts

The gravel orders were repeatedly made and delivery after delivery entered the yard. These were loaded onto the tracked dumper and moved to where they were needed in the river before being placed with the excavator. Trip after trip, tonne after tonne, the gravels were moved and introduced. The dredged channel appeared to eat the gravel up without as much as a burp. It rapidly became clear that our 200 tonne allocation was looking decidedly insufficient. Without more gravels the river would be passable, however the habitat would be lacking with wide, deep, sluggish pools similar to that of before. The budget was checked and with a groan it relinquished more funds. By the close of play, 360 tonnes of stone have been introduced and the transformation now complete, although further narrowing and planting would help this stretch further but with budgets as they are this will have to wait.

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Before looking upstream…

and after

and after

The upper line of posts has drowned out the bridge footing, providing a depth of approximately 300mm for fish to pass. From here, each ramp reduces the one metre head over the length of the site in approximately 100-120mm increments. The water now flows through the low flow channel in the form of a beautiful, streaming, passable flow.

Passable streaming flow through the low flow notches

Passable streaming flow through the low flow notches

With the works completed last Friday and with no time to settle in the site was brutally tested by the apocalyptic weather that we experienced at the weekend. With bated breath I pulled up on-site this morning and was pleased to see that it had passed, everything was where it should have been. The river has started to react positively to the works. Deep pools have been scoured out, kicking the gravels up to form shoals and riffles. The varied positioning of the low flow notches in each line of posts are creating a sinuous, meandering channel. Already a mosaic of habitats are being created which will provide the required niches for various inhabitants of the river to occupy. The rubbish strewn, brick filled bed has now been replaced with nice clean gravels. Fish can now freely migrate up and downstream as they choose. A few tweaks will be required to the levels as the river adjusts and settles into its new form but essentially the job is done.

Deep pool and riffle

Deep pool and riffle

Deep pool with root structure habitat and gravel shoal

Deep pool with root structure habitat to the left and gravel shoal downstream

A big thank you to Chris at Woodland Environmental for kindly allowing us to access the river through their site, without this we really would have struggled. Thank you also to Cain Bio-Engineering http://www.cainbioengineering.co.uk/ for helping with the design solution. And a huge thank you to the guys from Aquamaintain (http://aquamaintain.com/), Ben Kavanagh,   John Mudd akaNorthern, Nick Gibbo Gibbs’on’ and Keith. They stoically took on every one of the 700 posts, laughed in the face of each of the 370 tonnes of stone and worst of all had to put up with me for a week on site (it beats being in the office).  They took pride in their work and have carried out a fantastic job with great effect. If you listen carefully enough you can hear the faint sound of fins clapping in gratitude.

Hogsmill weirs: The two off Old Malden Road (part 1)

The Trust is continuing with our mission to improve connectivity for fish passage along the length of the Hogsmill River which flows from Ewell to Kingston.

As a brief recap to the project, the Wandle Trust has received funding from Defra, through the Catchment Restoration Fund, to improve connectivity along the Hogsmill River. This is because fish passage has been identified as being a major contributing factor to the river’s current failing status under the European Union’s Water Framework Directive (WFD). At the start of the project there were 15 obstructions along the 6 mile length of the Hogsmill, resulting in the available habitat, of which much is heavily degraded, being highly fragmented and therefore limiting. This causes bottlenecks at varying life stages, ultimately leading to the survival of the fish species present being compromised and extremely vulnerable.

Following on from the recently completed project in the Hogsmill Local Nature Reserve in the headwaters of the river, where two weirs were removed and the channel renaturalised, we have now moved our focus for the time being to the middle section of the river where two obstructions lie near to the Toby Carvery pub off the Old Malden Lane/Worcester Park Road.

The problem here is twofold. Firstly, as the river flows under a bridge, the concrete footing which is 18m long and 9m wide causes the water to flow incredibly shallow. At the downstream end of this there is a lip with a head drop of approximately 200mm. The combination of these factors  forms an obstruction, especially during low to moderate flow conditions.

The second issue is that 60m further downstream there is a weir very similar to those that we recently removed. The weir is 7.5m wide with a concrete apron and sill with a head drop of 0.7m. This is a complete barrier at all times. The river through this stretch has historically been excessively dredged and as a result is over-wide, deep and with all of the gravels having been removed leaving a barren, lifeless clay bed. The project will also address these habitat issues.

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The upstream bridge footing…

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and the downstream weir

The solution that we have come up with, with design advice from Cain Bio-Engineering http://www.cainbioengineering.co.uk/, is to once again completely remove the downstream weir, including the abutment walls. This alone would not rectify the problem. Firstly, the bridge footing would still be impassable but secondly the fall from the bridge footing to the downstream bed level  is too large. If left to its own devices, erosion would cause the footing to become undercut and a series of large, impassable cascades being formed.

To remedy this, a series of 8-9 rock ramps will be installed to stabilise the bed and drop the river in 100-120mm increments. This will be achieved by driving in untreated chestnut posts to form a curve from one bank to the other. Narrow gaps will be left between each post and large gravel rejects will be placed upstream of these to essentially create a mini step. The posts will be driven deeper to create a discharge point which will be approximately one metre wide. The positioning of the discharge point will vary from one rock ramp to another to help create a sinuous channel through the reach. The positioning of which will be governed by the current topography which will become uncovered as the downstream weir is removed. The top ramp will be positioned to drown out the bridge footing by approximately 150-200mm to allow fish to pass.

Creating a low flow channel will help to build  the river’s resilience to potential climate change. Once the rock ramps are in, gravels will be introduced to narrow the over-wide channel, also creating a low flow channel between each rock ramp. The gravels will additionally provide vital habitat for varying levels through the food chain from plankton to invertebrates to fish.

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The upper line of posts going in with the weir being removed in the background

The weir being broken out

The weir being broken out

The Trust has brought in the help of Aquamaintain (http://aquamaintain.com/), a local contracting firm who specialise in all things fishy and watery. The company is run and site managed by Ben Kavanagh, with Northern John, Nick Gibson and Keith making up the team.

One week into the project, things are going very well. The preliminary tree clearance to gain access has been undertaken, a track way has been cut into the bund along the length of the site to transport materials back and forth, and as I left site this morning, the fun bit, the first half of the weir was being broken out. A big thanks also needs to go to Chris of Woodland Environmental who has kindly agreed to grant us access to get to the river through his land.

Further updates to follow shortly.

You are invited to the Launch of the Living Wandle project on World Rivers Day!

In June we reported the news that the River Wandle had won the lottery! This triumph was a £2 million award from the Heritage Lottery Fund’s Landscape Partnership Scheme involving 25 projects to be delivered by a whole host of organisations on the Wandle.

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The project is going to be ‘launched’ on World Rivers Day – Sunday 29th September 2013 – at Morden Hall Park. All the organisations involved will be there to tell you about the exciting projects that are coming up over the next 4 years.

The Wandle Trust will be leading on 4 projects – A river education programme for schools, a pollution awareness project called ‘River Guardians’, some physical river restoration work which will build on the enhancements already being delivered and a project called ‘Discover the Source of the Wandle’ through which we’ll investigate local features and landscape as well as archived records to look for signs of where the Wandle starts flowing.

Further details on the event, including the event booklet, can be found here.

So come and join us at Morden Hall Park on World Rivers Day and hear about these and other projects (including an invasive species programme, oral history and community theatre projects and the opening up of Merton Priory’s Chapter House). The Wandle Piscators will also be at Merton Abbey Mills that day with a range of activities so why not take a Sunday stroll along the Wandle between Morden Hall Park and Merton Abbey Mills and join thousands of others around the world appreciating their local river on World Rivers Day!