Tag Archives: Hogsmill

Riding for Rivers, London to Brighton Cycle Ride

Last Sunday, Nick and I rode 54 miles in the name of rivers, completing the London to Brighton cycle ride. This blog is our way of saying thank you to all of those who supported and sponsored us along the way.

(If you’re worried you missed the opportunity to sponsor us, you still can, so never fear! The links are below)

http://www.doitforcharity.com/NickHale

http://www.doitforcharity.com/THull

So why on earth did we agree to cycle 54 miles?

Well, to be honest it was a mix of thinking “Ride4Rivers” was a catchy slogan, and being asked to do it when we under the influence in the pub. Before we knew it, our cycling jerseys had arrived in the post and we were beginning a countdown to Sunday 17th September.

What was Ride4Rivers?

The Ride4Rivers team was organised by the Rivers Trust, inviting local trusts and volunteers to raise money and awareness for their local river by joining the London to Brighton cycle ride. In the team were myself and Nick, other rivers trust staff and volunteers, and riders from Five Rivers and the Angling Trust among others. All the money raised by the Ride4Rivers team will go back to the Trusts and help further work to protect and enhance our river ecosystem. So how could we say no really?

The BIG Day

The Ride4Rivers team gathered early in the Sunday morning at Clapham Common with over 4000 other riders.

The team respectfully giving space and attention to the fuel for most to get started, coffee

Within a few miles we came to Hackbridge where the route offered a perfect photo opportunity overlooking the site where we removed four weirs and undertook significant restoration work back in 2014 on the Wandle – with Nick working for us as the contractor at the time!

The river was looking splendid, but there wasn’t time to stop for long, and shortly after we were passing the source of the Wandle at Carshalton Ponds.

A quick pit stop to admire the Hackbridge restoration work

The flat ground of London soon turned to numerous steep climbs as we ascended the North Downs. Fortunately however physics was on our side as what goes up must come down. Soon we had gravity helping us as we descended into the Weald. The atmosphere among all was great as we pushed on mile after mile. Our stomachs began to grumble but the organisers had this covered by laying on an absolute feast at Mile 29, the only thing being they made us work for it by locating the lunch at the top of a steep hill.

Feeling energised if somewhat seized up, progress after lunch began well but then… psssss, Nick got a puncture on his rear tyre. Now I mentioned that neither of us are cyclists, it would appear that since being children our memory of how to replace an inner tube was a little hazy. Sometime later (and with a little help it must be said) we were back on the road.

Sad face

A noise continued to be emitted from my bike that had developed since lunch.  Some 12 miles later as we approached the infamous Ditchling Beacon the noise finally got to me and I figured I should have a little investigate. It appeared that I had been riding with my brake partly on since lunch. Well I didn’t want to make it too easy! Again with our bike maintenance knowledge lacking after a little more unsuccessful fumbling the only thing for it was to disconnect the rear brake.

Ditchling Beacon soon loomed over us and the climb was on, one mile of uphill struggle lay ahead but we were not going to be defeated and soon we summited to spectacular panoramic views with the sun coming out on cue.  More unsuccessful fumbling to reinstate my brake, meant a bit of a hairy descent down to Brighton but who cared, from here it was all downhill to the finish line, the end was near and the prospect of a pint alluring.

Ditchling Beacon summited

We both need to say a massive thank you to all of you who so kindly donated to Ride4Rivers – your backing was so valuable to encourage us along, not to mention the benefit it will bring in helping us to enhance, restore and protect our rivers. Thank you so much! Nick and I also need to thank Steve Wright, Luke and Sam for lending us bikes so that we were able to take part – otherwise it would have been a long walk.

A well earned beer

If you wanted to sponsor, but missed out then our fundraising pages are remaining open for another couple of months so please do give what you can in support of our local rivers.

http://www.doitforcharity.com/NickHale

http://www.doitforcharity.com/THull

 

Knowing your rudd from your roach

Our lucky Pollution Patrol volunteers were treated to a FIN-tastic day with our local Environment Agency team, learning all about fish.

It may come as a surprise to some people, but the Hogsmill, Wandle and Beverley Brook all contain a variety of different fish species. Common species across all three rivers include chub, dace, roach, barbel, stickleback and European eels.

But how do you tell the different between these species? For some, it is easier than others. The European eel is quite distinctive compared to the others for example. But as to the rest, it’s a bit more difficult.

Tom Cousins, a local EA Fisheries Officer, started the day for us with a presentation on the different fish species and the key identifying features.

The diagram below shows the external morphology of an average fish, and the features that help us distinguish one species from another.

For example: Roach and Rudd

These two fish are quite similar in appearance, both large-bodied with reddish fins. So how can we tell them apart? The answer is by looking at the mouth.

The roach is a bottom feeder, and its mouth points downwards, with the upper lip over-hanging the bottom lip – whereas a rudd feeds from the surface, and therefore the bottom lip overhangs the top lip.

The presentation from the Environment Agency is available below for you to download, with many more tricks and tips for ID.

Fish ID Presentation

As part of the training day, we also got to witness the Environment Agency’s electrofishing survey at Morden Hall Park on the River Wandle in South London.

It was amazing to learn about the fish in the classroom, and then come outside and see some in the flesh. Each fish caught was measured, and scale samples from some were taken in order to age the fish.

Once they had been recorded and had recovered, they were returned safely back to the Wandle. 

Many thanks to Morden Hall Park for hosting us and to the Environment Agency for running the event!

Hogsmill Newsletter: May Edition

The latest edition of the Hogsmill Newsletter is now available to download. It summarises the results of River Monitoring Initiative (RMI) sampling together with other pollution monitoring and activities and events along the river.

Hogsmill Newsletter May 2017

If you have any comments or suggestions about the newsletter please contact:  Peter Short: rpetershort@hotmail.com

River Club Weir Removal

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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.

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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!

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

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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.

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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.

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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

Keep up to date with the Hogsmill

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There is a new newsletter for anyone interested in or involved with the health of the Hogsmill. It summarises the results of River Monitoring Initiative (RMI) sampling together with other pollution monitoring and activities and events along the river.

Hogsmill Newsletter March 2017

If you have any comments or suggestions about the newsletter please contact:  Peter Short: rpetershort@hotmail.com

Volunteers Join Forces for the Hogsmill

The Hogsmill river doesn’t know how lucky it is!

Last week, 30 volunteers joined SERT and ZSL at London Zoo for the 2017 Hogsmill Forum.

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The Forum is an opportunity for us and ZSL to say thank you to all the volunteers who help us with our projects on the Hogsmill – Pollution Patrol and the Riverfly Monitoring Initiative.

It is also a chance to share wider plans for the river with the local community,  discussing ideas and actions for the coming year; all of which feed in to the Hogsmill Catchment Partnership which SERT host.

If you are interested in either project, get in touch – volunteering@southeastriverstrust.org

And why not have a read of these presentations which our speakers delivered through the course of the day?

Presentations:

Many thanks to ZSL for hosting us, and for letting us have a look around the zoo after the meeting!

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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.

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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.

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

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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.

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Out with the old…

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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.

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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.

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

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Getting into the flow of things

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Half way!

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

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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:

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About to ‘pull’ the dam

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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.

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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.

 

Get ready for London Rivers Week 2017

Get your diaries out and calendars open, the dates for London Rivers Week 2017 have been confirmed!

LRW logo finalLondon Rivers Week 2016 brought together many partners across London, delivering a total of 35 public events to get everyone involved with their local river. This year, we want to make it even bigger and better.

London Rivers Week 2017 will start on Monday 26th June and run through to Sunday 2nd July. During this week, organisations across London will put on a variety of river themed events including cleanups, guided walks, information talks, citizen science taster sessions and more.

To find out more about London River Week, check out the Thames 21 website page where all the events will be listed: http://www.thames21.org.uk/londonriversweek/

Until then, keep your eyes peeled for more details on what is to come!

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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!

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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

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The Hogsmill: A Work of Art

You may remember that earlier this year we were lucky enough to spend a week in the Hogsmill with the Lower Mole Partnership. It was a chilly week in March but all our volunteers were enthusiastic and we managed to restore 500m of river through the Hogsmill Local Nature Reserve. With wood from the local area we created 9 brash berms, narrowing the river to increase local flow diversity. We pulled out 48 railway sleepers to reconnect the river to a natural bank, and in more difficult places we naturalised the bank with pre-planted coir rolls. A busy week to say the least.

hogsmill-merge

What we weren’t aware of was that Peter, from the Lower Mole Partnership, turned our week in the river into a work of art. Check it out…

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It was such a great week and we hope to be back again – with another painting!

Outfall Safari on the Hogsmill

ZSL and the Hogsmill Partnership are looking for volunteers to help us map polluted outfalls on the Hogsmill this October.

While walking the Hogsmill you may have noticed all the different pipes that can be found along the river bank. These pipes are usually part of our surface water infrastructure, transporting clean water from our roads and roofs into the river. However in some cases, these pipes or outfalls can be polluting the Hogsmill as they have been misconnected.

Polluted Outfall

Misconnections are a BIG issue for urban rivers and the Hogsmill Catchment Partnership have been working hard to start addressing this on the Hogsmill River.

A misconnection is when a toilet or washing machine has been connected to the surface water drain heading straight to the river, instead of the sewer system. You can read more about misconnections at on the Connect Right website.

Connect Right

This October, ZSL are running an Outfall Safari to map all these pipes heading into the Hogsmill, and assessing their condition to check for misconnections.

Volunteers will receive training on how to recognise signs of pollution at these outfalls and record the pipes on a new smartphone app. This survey data will greatly improve our understanding of the river system and help to target sources of pollution.

Interested?

If you would like to join the team, you can sign up on EventBrite to register your interest. Once you’ve registered, more information will be sent to you about where and when the training sessions will take place.

Sign Me Up!

For more information contact by email: Joe.Pecorelli@ZSL.org, or phone: 07974 725 557
Outfall BannerPlease register your interest to help at: hogsmilloutfalls.eventbrite.co.uk

You’ll need to read this before your training session: 2016-Pre-training-information-for-Hogsmill-Outfall-Safari-Volunteers..pdf

New London Partnership Project to tackle Urban Pollution

We have teamed up with Thames 21 on a new project to tackle urban pollution across London’s rivers.

Many improvements in the quality of urban rivers have been made in recent years, but lots of serious water quality issues remain. One of the biggest issues is ‘urban runoff’, where a toxic mixture of contaminants derived from urban areas drain straight into rivers.

With surface water drains often running straight into rivers, these contaminants are washed directly and unfiltered into urban rivers when it rains. During these ‘first flush’ events, river water often changes from being clear and colourless to being an opaque grey-black colour, and water analysis shows that a complex mixture of hydrocarbons, fine particles, nutrients, microorganisms and heavy metals are the cause.

First Flush samples from the River Wandle

First Flush samples from the River Wandle

In urban areas the contaminants causing rivers to run grey-black in colour may have a greater impact, but the locations at which they enter a river are often unknown, and they are relatively costly to survey, with samples needing to be processed by a lab.

Our project with Thames 21 is testing a low-cost sampling method that can be used by volunteers to identify complex urban contamination. In particular, it aims to investigate Surface Water Outfalls (SWOs) which discharge contaminated urban runoff into London’s tributaries of the River Thames.

The method being developed is based on evidence from data collected on the River Wandle, and urban sites in Wigan in NW England, which show that Total Suspended Solids (TSS) are strongly correlated with several important heavy metals and E. coli (a bacterium which can indicate faecal matter) and can therefore be used as a low-cost proxy to identify problematic concentrations of these contaminants.

The next step in this project is for us and Thames 21 to create Pollutant Profiles for our rivers to see if they match this correlation. You can follow progress on the project on our Twitter feed @SE_Rivers_Trust with #TSS!

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.

The 2016 Hogsmill Forum

The Hogsmill River may have its problems, but it is one of the lucky urban rivers to have huge community support and many enthusiastic volunteers.

We run our Pollution Patrol on the Hogsmill, tracking down polluted outfalls and misconnections. While ZSL run the Riverfly Monitoring Initiative which uses the kick sampling of invertebrates to check for organic pollution.

So to thank everyone for their hard work, both projects combined for a joint Hogsmill Forum – kindly hosted by ZSL at London Zoo.

Hogs Forum

The event was a huge success with some really interesting discussions on the priorities for the Hogsmill going forward. Below you can download PDFs of the presentations.

Presentations:

 

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.

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Happy Anniversary to the Hogsmill Pollution Patrol

Pollution on the HogsmillWith the start of 2016 comes the One Year Anniversary of our Hogsmill Pollution Patrol scheme – and what an amazing job it has done so far!

Throughout 2015, our trained volunteers have been monitoring 15 outfalls on the Hogsmill for signs of pollution such as misconnected appliances and sewage discharge.

Together they have submitted 470 reports of pollution to us. Working with the Environment Agency and Thames Water, we have been able to start investigating these issues and begin work towards rectifying them to improve water quality on the Hogsmill River.

To read the latest update of our work, please download our Newsletter below.

Pollution Newsletter December 2015

If you see pollution on your river, call the Environment Agency hotline on:

0800 80 70 60

Pollution

Polluted Outfalls and Riverfly Monitoring

Last week I was lucky enough to visit the Hogsmill River twice with some of our dedicated Pollution Patrol volunteers.

The Team!

From left to right: Geoff, Me (Polly), Steph, Peter, Bill and Jan

Our Pollution Assessment Volunteers (PAVs) work hard to track down and monitor polluted outfalls on the river, sending reports to the Environment Agency for action.

On Wednesday we were joined at a particularly bad outfall by our local Environment Agency Officer Steph to take some samples.

Sewage Fungus

Sewage fungus at the outfall

Steph sampled for ammonia, which is used as an indicator of raw sewage entering the river, and for oxygen available to river invertebrates and fish. Oxygen is a good indicator of how polluted an outfall is, as bacteria use up oxygen to break down organic pollutants, which reduces oxygen available to other species which can sometimes result in fish kills.

Sampling for Oxygen

For this week, both readings were fine.

This is one of many outfalls we’ve been looking at. You can find Steph’s updated report here.

Hogsmill Report July 2015

On Friday I was invited along to the monthly Riverfly Monitoring session at the same outfall with the same dedicated team. Every month they get together at this location and take a kick sample of invertebrates as an indicator of how healthy the area is.

Riverfly Monitoring

Some invertebrates such as caddis flies are very sensitive to pollution and are therefore an excellent indicator of water quality. If this is something you might be interested in, check out the website here!

Thank you to all our volunteers working on the Pollution Patrol scheme – we are making progress!

What have we been up to?

We have had a busy start to 2015 – maybe it is time for you to catch up with what we have been up to?

River Restoration ~ Luke has been busy transforming the Ravensbury Park Back Channel on the River Wandle for both the local community and wildlife. Read all about his progress here.

Pollution Control ~ Olly has been working hard trialling new methods to mitigate against urban diffuse pollution. We have trialled Siltex in Carshalton Ponds and installed Mycofilters at problematic outfalls.

Looking Forward ~ We’ve got restoration projects this year on the Hogsmill and Beverley Brook so keep your eyes peeled for more updates!

First Class Degree in Fish Passage at Kingston Uni

When working in channel you really are dependent on dry weather conditions. This is especially so on the Hogsmill which acts like a spate river, with large flashy flows shortly after rain events.  I have been incredibly fortunate with the weather for a long run of things. Unfortunately, things had to change and change they did. I return from site after a wet and challenging month.

The Hogsmill splits just upstream of the Knights Park Campus at Kingston. There is a large head weir on the main channel and on the side channel, two lower head weirs at either end of a sloping 24m concrete spillway. Both channels were completely impassable to fish, with the exception of eels on the main weir thanks to the eel pass installed by the Zoological Society London (ZSL) and monitored by the University.

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The upstream weir flowing onto the sloping concrete spillway

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The downstream weir with shallow plunging flows

Addressing passage on the main weir would be both feasibly and financially unviable. Instead attention was focused on the side channel. The water flowed over both the side channel weirs in shallow, plunging flows and over the spillway it was fast and shallow. Kingston University kindly agreed to the Trust carrying out the work as continued partnership working following on from the habitat works carried out earlier on the year at the Campus.

The chosen solution was two-fold. A rock ramp would be built at the downstream weir to step the river down in the form of a passable channel. On the concrete spillway four lines of rock would be fixed to the bed. Varying sized gaps (notches) are left in each line so that water is retained in the channel even under low flow conditions and a variety of pass conditions are provided. These rock lines serve to back the water up, increasing depth and slowing velocities. This backing up then effectively ‘drowns out’ the top weir which would also be ‘notched’ to reduce the height.

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Notching the upper weir

Roo Newby from Aquamaintain was brought in to give a hand, whilst gracing me with his northern charm and banter. The first job was to create a dry working area. A cofferdam was set up at the top of the channel to direct all of the flow down the main channel.

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The cofferdam in place, in theory providing a dry working area

The next job, which took the best part of three weeks, was to place all of the 20t of stone into position in order to create the desired flow conditions. With incredibly limited machinery access to the channel, the chore of moving it all fell to Roo and I. We grunted and moaned our way through it, placing, moving and repositioning each stone several times before finally fixing them. By the end of the job we have grown muscles on our ears.

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The boulders placed into position on the spillway

Key stones on the spillway were fixed into position by drilling through them and into the bed. The hole in the bed was then cleaned and a section of steel rebar fixed with resin. The stone was then lifted and fitted snugly back onto the bar.

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Using resin to fix the rebar into the holes

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The line of rebar to secure the upper line of boulders of the rock ramp

The key stones and all other non-load bearing stones, were concreted into position. The key stones in the rock ramp were secured using multiple techniques. At the downstream end of the ramp, chestnut stakes were driven into the bed to stabilise the lower line. The second line relies on mass and by being keyed in by the rip rap rock on either side. The third line was concreted onto the existing weir apron. The upper line of stone sits on the weir sill and was secured by the resin and rebar technique.

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Roo ‘mucking in’ the third line of boulders in the rock ramp

The job was hampered by mizzly conditions to start followed by heavy rain. Roo and I then both succumbed to river lurgy, no doubt caused by the sewage in the river as a consequence of combined sewage outfalls flowing after the rain, in combination with the massive misconnected drains issue present throughout the catchment. The heavens continued to open with annoyingly frequent regularity resulting in several days having to be abandoned due to a flooded working area. The rain built up to a crescendo with apocalyptic volumes falling last Sunday, giving the work a true baptism of fire with the cement barely having time to dry. But it stood up to the battering.

With the exception of the upstream weir, the rest of the work would now be passable for elvers (young eel) and eels. To assist them past the upper weir, a ramp of concreted in stones was installed to provide climbing media for them to get up and over. They can now continue onto the next stretch of river. During the work, four elvers were found in the channel. This pleasingly and clearly demonstrates that the past work of installing eel passes on the weirs downstream is working.

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Eel passage through the rock ramp…

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and over the upper weir

Both weirs have been drowned out with average depths of 300mm through the rock ramp and up the length of the spillway. A diversity of flows throughout the work provides passable notches and importantly vital resting pools. Perturbation boulders break up the most intense flows, adding complexity as well as potential habitat.

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The lower weir before the work

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The rock ramp in place

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The rock ramp working under moderate flows

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Looking up the spillway at the upper weir

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and after where the upper weir has been drowned out (note the complexity of flows and slack resting pools

Before the work was even completed, we saw two fish using the rock ramp, giving real confidence that the design was working and demonstrating their real desire to push their boundaries. With the University stretch being the most prolific for fish in the whole river, the door has just been opened for them to begin to repopulate upstream.

Thanks to Kingston University, specifically Sivi Sivanesan for allowing and assisting us with this project. A BIG thanks for all the hard, back breaking work from Roo from Aquamaintain and to Jack for his days on site.

Of rock-ramps and fish

And the fish easement work on the Hogsmill continues. This time our work is focused on the river around the Thames Water Sewage Treatment works situated in Berrylands, Surbiton, specifically the stretch from the railway bridge down towards Kingston Cemetery.

The over-widened channel here reduces water depth which, along with three small weirs and a lot of concrete-lined channel in between, effectively prevents fish from moving upstream.

So these weirs will have to go. Or will they? Toby’s work connecting reaches of the Hogsmill to free fish movement has shown an alternative – slow the flow and over they go! Building rock ramps and pool passes drown out these structures enabling fish to navigate their way over them.

Illustration of a typical rock-ramp (Source: Thorncraft and Harris, 2000)

Illustration of a typical rock-ramp (Source: Thorncraft and Harris, 2000)

After a few essentials from the Environment Agency, Thames Water and Network Rail we ought to have this project going in the next couple of months. More to follow shortly…

Reference

Thorncraft G. and Harris, J.H. 2000. Fish passage and fishways in New South Wales: A status report, Technical Report 1/2000 prepared by NSW fisheries for Cooperative Research Centre for Freshwater Ecology.