Newsletter – Autumn 2019

Lapwing can be seen on the Thame floodplain in Autumn as they migrate from northern Europe to overwinter. Credit: Doug Kennedy

We are pleased to welcome you to our Autumn 2019 newsletter! We hope you enjoy reading about what we and our partners have been up to recently. If you have any suggestions for our Winter newsletter then contact: enquiries@riverthame.org


A word from the CEO

We have certainly had a busy summer and autumn so far!  Thank you for all your support and particularly, thanks go to those who have made very unexpected, but much appreciated, financial donations to the Trust.

The summer and early autumn period is always busy.  In theory, dry weather and low flows allow us to deliver the projects that have been planned and funded during the previous Winter and Spring.  This year, our big projects (read all about them in the articles below!) were successful in spite of the weather which started as glorious sunshine and ended in prolonged rain and high water levels!

The autumn is upon us and winter not far away.  This is now the time for the important forward planning and budgeting.  We are working closely with the Environment Agency, Thames Water and other funders to frame the budgeting and programme for the New Year.   We have an unprecedented list of potential projects on the list and a real ambition to work on even more – given the funding!

Lastly, thank you to our many unsung hero volunteers who have turned out to support numerous days of removing the spread of invasive species, to monitor water quality and bird populations across the catchment.  This regular background data gathering is really important and allows us to plan and prioritise our future work as well as argue for new site protections and designations – especially in the face of the continuing threats of development!

Nigel Davenport


 

Habitat Works

Waddesdon wetland complex

RTCT has been busy this autumn undertaking phase I of a floodplain restoration project that will transform an area of low diversity floodplain meadow into a large wetland complex designed for specifically for biodiversity. This project is run in partnership with Freshwater Habitats Trust, the Waddesdon Estate and Aylesbury Vale District Council. Thanks also to the local EA officers and EA Biodiversity team in particular for their support throughout the project.

Slideshow of photographs from the works

The site

The meadow is located on the floodplain of the River Thame and consists of c.10 ha of floodplain grassland. The extent and location of the meadow provides an excellent opportunity to create a complex of wetland habitats to benefit freshwater and other wildlife in the area, and to contribute to ecosystem services (e.g. flood prevention and nutrient cycling) and ecosystem resilience.

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The new wetland mosaic, will be the first of its kind in the R. Thame catchment and will improve landscape-scale connectivity, adding a ‘stepping stone’ between two of the best locations for wetland birds in the catchment, the nature reserve at the Aylesbury Sewage Treatment work to the east and the Waterstock meadows to the west.

In the longer-term, the new wetland complex could also provide a range of other benefits, for example a focus site for the re-introduction of freshwater plants and animals whose populations are declining or have become extinct in the River Thame catchment, and a national best practice demonstration site for floodplain wetland restoration.

The design

Design for Waddesdon wetland and backwater

The wetland complex creation scheme will aim to maximise the diversity of the site for wetland plants, aquatic and semi-aquatic invertebrates and amphibians. A range of waterbodies will be created of varying shape, size and depth. These will all have wide shallow sloping margins, providing a long drawdown zone which is ideal for plants and invertebrates, and have varied topography, with lots of small bumps and dips to maximise the available micro-habitats.

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Some waterbodies will dry out annually, some will dry out infrequently and some will hold water all year round. The complex will remain unconnected to the river, as unfortunately the river suffers from poor water quality, and be primarily fed by rainwater. Allowing areas to dry out will also help to remove any nutrients that build when the river is in flood and covers the site. The varied habitat features and aspects designed to maintain good water quality will provide a high diversity of good quality habitat, enabling the best biodiversity gains.

In addition, a large backwater attached to the main river channel will be excavated. A large online pond that will provide refuge for fish during high flows and key nursery habitat for juveniles. As with the complex the backwater is designed with wide shallow sloping margins to ensure there are always areas of shallow water with warmer water to aid juvenile development and where young fish can avoid predation.

Both features will benefit a huge host of species ranging from tiny water beetles to stalking herons, flitting bats and foraging otters.

The Excavation

The works are planned to be carried out in two phases over the course of two years. The first phase was carried out this autumn and the second is planned for autumn 2020.

Phase I included the following works:

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  • Topsoil strip – The topsoil was stripped down to the underlying clay from the entire wetland complex area (11,300m2) and removed to a nearby arable field outside the floodplain. Stripping the topsoil removes built up nutrients in the soil left over from historic fertilizer application and will help to ensure good water quality for the wetland.
  • Test pits – Within the stripped area a series of test pits were dug ranging in size, location and depth. Water levels within the pits will be monitored over the coming year and used to inform phase II of the dig, allowing the design to be tweaked before the remainder is excavated to ensure the wetland holds suitable water levels.
  • Backwater excavation – Backwater excavation work began this autumn. A surface area of 3,400m2 was stripped of topsoil and then excavated down to create a large pool. This has not yet been connected to the river as unfortunately works needed to be suspended due to a change in weather and ensuing storms making ground conditions unworkable. The remaining spoil will be excavated during phase II and edges moulded to create further diversity in microhabitats.
  • Ditch management – Although a truly man made feature, ditches can also provide great habitat as long they have good water quality, much like all other freshwater habitats. Along the site edge runs a ditch that has filled up with high nutrient silt. Slightly experimental management was undertaken on this ditch line to remove built up high nutrient silt, improve water quality and to see what plants might germinate from the floodplain seedbank.

Project funded by:

 


Fish passage and river habitat works – near Cuddington

After months of design, planning and preparation and with all permissions and permits in hand we were finally ready to carry out the physical works to improve fish passage and habitat on the River Thame near Cuddington. This is the exciting part of any project and why we do our jobs; to deliver real improvements for the river and its wildlife.

Read on for a detailed summary of the project design and delivery – with lots of photos!

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The issues – fish passage

Cuddington mill, as is typical with most mills, has a weir associated with it that is a barrier to fish movement. Fish need to be able to move between habitats to spawn, feed and find new habitat. Fish passage is therefore important for the resilience of populations of all fish species in the River Thame.

Approximately 800m upstream of Cuddington mill, on private farmland, the main river splits into two to create a mill leat taking most of the flow to the mill and a second channel (the original river course) that goes around the mill.  This channel has the potential to be a natural fish bypass channel to the mill weir.

However, at the head of this channel there used to be an old weir that was part of the water management system controlling the amount of water going to the mill. In the late 1990s the weir was in poor repair and rock was placed over the weir to create a rock ramp weir.

The original weir in the 1990’s (Pic credit: Andy Killingbeck EA)

Rock  ramp weir in 1997 (Pic credit: Andy Killingbeck EA)

Over time the rock had moved around and the structure had degraded and become overgrown. Assessment in 2018 showed the rock ramp weir to be impassable to fish at most lower flows – particularly spring and summer flows.The degraded and overgrown rock ramp weir in 2018

…and in 2019 with trees cut back showing the degraded & impassable structure

The issues – habitat

As well as the fish passage issues, over 40 large unmaintained willows had created almost complete shading of the river channel downstream of the weir with minimal bank and instream aquatic vegetation present as a result.  Previous dredging of the channel had also created an overwide uniform channel with little variation in flow. This combined to make a poor habitat for fish in particular but also invertebrates and macrophytes.

The solutions

The project that we designed and implemented had 2 main aims:

  1. To create fish passage and habitat connectivity around the mill at all river flows, for all species of fish and all life stages. Any solution needed to be robust and not degrade over time.
  2. Improve fish, as well as invertebrate and plant habitat, on 400m of the river downstream of the rock weir by improving light  penetration, creation of marginal habitat and river narrowing.

The solutions – fish passage easement

To design the fish passage easement for the weir we carried out surveying, flow and level gauging to gather data to allow us to determine the physical parameters required to make the pass passable to all fish sizes and species at all flows and in particular low flows.

surveying the structure                                    flow and level gauging

The solution was to create a rock ramp comprising of 5 lines of boulders each with a notch in it and pools between. The lines of boulders step down the height drop in small manageable drops and ensured suitable hydraulic conditions. The notches determine the amount of water flowing through the pass at lower flows and the notch dimensions and levels were set to ensure all species and life stages of fish could swim up and downstream at all flows, particularly lower flows.

Seventy large Purbeck stone boulders were delivered and arranged on the bank into 5 suitable lines that could be installed onto the weir.Rocks on the weir were removed to create trenches into which the boulders could be accurately placed at the correct heights using a laser level.

A jigsaw with a difference! selecting the rocks for the fish pass

carefully and accurately placing the boulders to the correct heights

The rocks in the lines were locked in to each other and the lines curved to create an incredibly stable arch structure. The curve also ensures flows are focused into the centre of the structure which reduces erosion risk in higher flows.  A geotextile material lined the trenches to trap fine sediments to create a more watertight structure.

The stepped boulder lines taking shape

Once the lines were in place the pools between them were formed and shaped by removing rock and then material of decreasing size added (larger rock from the old weir followed by gabion stone then flint gravels and finally sand) and shaped to create a locked in stable structure resistant to erosion and a relatively watertight structure. Large boulders were added to each pool to dissipate the force of the flows into each pool, ensuring smaller and species with lesser swimming ability could still pass.

Notched rock lines and pools – awaiting gravel addition and final landscaping of the banks

Nearly done – adding gravels to the pools

We were lucky that nearly all of the fish pass work was able to be carried out before some prolonged rain at the end of September caused the river to rise and drown out the work site! Water levels are an occupational hazard with this sort of work and there is often a fine balancing act between ensuring work is carried out at the correct time of year for wildlife and trying to ensure risk of high water is minimised.

Fish pass? what fish pass?!

The solutions – habitat work

Once the fish pass was complete it was onto the habitat work. Branches were selectively removed from trees to let in light to the river and banks and to create brash material to be used in the river as berms.

 

Cutting trees to create brash for use in the river and increase light

The berms create scruffy marginal habitat features that reduce the width of the river and vary both flow speed and direction providing different niches for a variety of fish, invertebrates and plants. The brash itself will provide good cover for fish from predators and should increase the fish holding capacity of the stretch.

Installing woody material to create berms

The woody material from the tree works was secured in the river using chestnut posts up to 2.5m long and a biodegradable manila rope. Over time these berms should trap sediment and become part of the bank and bed structure.

One of over 20 finished berms

The final part of the project included creation of 3 cattle drinks. Cattle poaching had destabilised some areas of bank and was creating significant sediment input in places. The cattle drinks were created in areas favoured by the cattle by grading back a section of bank, addition of gabion stone topped with gravel to create a firmer base. This was followed by some limited fencing to funnel the cattle to the feature and limit encroachment into the river.

One of the cattle drinks

….and another cattle drink

Again the rain caused some issues for us and we had to install many of the berms in flows that were higher than we would have liked – but we managed to finish before the river started to overtop its banks!

The River overtopping  its banks after works were completed

So, all in all a satisfying few weeks of hard work resulting in 1 fish passage easement, 40 large willows trimmed, over 20 woody berms installed and 3 cattle drinks created!

A big thanks to our contractors (Amenity Water Management), funders (The European Agricultural Fund for Rural Development), the landowners for permission to carry out the works (A+M Spencer Bernard Trust) , and the grazier (Ray) for keeping the cattle out of the fields for the duration of the works! Thanks also to the local EA officers for their support throughout the project.

Funders:


 

Clean water ponds and great crested newts in Shabbington Woods: a success story

By Dr Pascale Nicolet, Technical Director, Freshwater Habitats Trust

Creating cleanwater pond habitat in Shabbington Woods

…..which were quickly colonised by newts and other amphibians

A recent analysis of all the freshwater wildlife data in the River Thame catchment has led to the designation of Shabbington Wood as an Important Freshwater Area. This is a direct result of habitat creation and collaborations between the landowner (Forestry England), Freshwater Habitats Trust and the Newt Conservation Partnership. It shows what can be done to help freshwater wildlife, with relatively little means, just by creating clean water ponds.

Read on to find out more about the exciting results from several years of clean freshwater pond creation……..

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Shabbington Wood was designated as a Site of Special Scientific Interest (SSSI) in the 1980s for its rare butterflies. Before various waves of pond creation began about 10 years ago, there was relatively little open water in the woods, except for  a handful of small ponds dotted here and there, and a few small streams. Although often wet underfoot, previously no one thought the woods were  an important place for freshwater wildlife.

Great Crested newt. Credit: Freshwater Habitats Trust

As part of the Million Ponds Project, 9 new ponds – 8 clean water ponds and one for dogs to play in – were created in 2011, specifically for great crested newt. All eight clean water ponds were colonised by these miniature godzillas by 2017.

In 2018, a further 5 ponds were created with funding from the Newt Conservation Partnership in another area of the woods.

 

One of the new ponds. Credit: Freshwater Habitats Trust

Follow-up monitoring by the Newt Conservation Partnership, with help from River Thame Conservation Trust staff, has shown that only one year after creation, 3 of the new ponds have great crested newt living in them already.

Hannah from RTCT carrying out newt monitoring  Credit: Freshwater Habitats Trust

All in all, our work has increased the number of ponds occupied by great crested newt from 2 to 17! **

The new ponds have very little vegetation and are  milky in colour because of the clay base. Some of the great crested newts caught in our bottle traps this spring have curious colours which matches the water colour exactly – probably so they are less visible to predators.

Newt with adapted colouration Credit: Freshwater Habitats Trust

These new clean water ponds also  provide habitat for a whole raft of plants and animals, including amphibians like smooth newt, common toad and frogs.

Tadpoles! Credit: Freshwater Habitats Trust

Because of a national decline in their population, the once common toad is now a priority species for conservation, so it’s very heartening to see them colonise our new ponds so quickly. This work to support our ailing wildlife has been very satisfying from a biologist’s perspective: ponds are quick to make and, with a little know how, quick to successfully provide new habitat for freshwater wildlife.

**note; we can’t guarantee that they are breeding in a pond until we find eggs or larvae. 

click here for the Freshwater Habitats Trust website

click here for the Newt Partnership website


 

Survey Network

RTCT bird surveys are 4 years old – what are they telling us?

 

Curlew stretching at Waterstock; credit Julie Cuthbert

Atlas coverage

December 2015 saw the first of our formal bird surveys carried out along the length of the River Thame and, as we now mark the completion of the 4th year, it is great to be able to thank our dedicated team of volunteers and celebrate the story the data is now starting to tell about the wildlife of the river.  Read on for a summary of the past four years and what it means…..

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With the fantastic support from the British Trust for Ornithology (BTO) we now run two major survey projects. Our Wetland Bird Survey covers 16 stretches of the whole river from its source north east of Aylesbury to its confluence with the Thames at Dorchester and our Atlas cover the whole of the wider catchment across 236 2km Tetrads.

Over 70 volunteers have carried out the surveys and we estimate that the collective contribution comes in at over 5,500 volunteer hours; the equivalent of a 3-year full time Officer role. This makes a huge difference to a small organisation such as the Trust.

In excess of 1,400 survey visits have been carried out; 26,000 records generated and 151 species recorded. These records are extremely powerful and have been shared with not only the BTO but our two Environmental Records Centres. This means the data is being used both in national trend analysis and informing local data searches requested by planners and other organisations.

The data is also helping us to highlight which birds use the River Thame, where they use it and is starting to tell us how they are getting on in both the breeding season and over winter.

The surveys have given us (among many highlights) 4 years of data for our local breeding curlew (one of the UKs most threatened breeding birds), evidence of breeding goosander (a local rarity) and records of significant local breeding and roosting sites for many of the resident owl species.

It is also supporting our work with landowners and informing practical work on the ground. This is highlighted in the work we have carried out at Waterstock that has led to the river’s first new Local Wildlife Site designation and the planning of new floodplain wetland habitat creation in the area.

Above all else the surveys are helping the Trust to put the River Thame firmly on the local wildlife map. Many have described the river as a wildlife desert and a poor relation to other areas but, thanks for the many hours of our dedicated volunteers, this story is changing.

Under recorded yes, undervalued definitely, wildlife desert absolutely not …..

Our surveys continue. We are fast approaching the start of our 5th year of the Wetland Bird Survey and the last year of the Atlas project (all 236 Tetrads have been allocated and we should reach 100% coverage of the catchment). If you would like to find out about how you can get involved or would like a speaker to come to a local community interest group please get in touch with RTCT at enquiries@riverthame.org or Nick Marriner (who oversees the surveys) at marrinernick@gmail.com

Thanks to the BTO for their support

 

 


 

Water in a Dry Landscape project update

Horsenden Stream at Saunderton – one of the headwater streams being looked at through the project

Volunteers carrying out water quality monitoring as part of phase 1

Volunteers have been getting stuck into helping with the Water in a Dry Landscape project (WIDL) to monitor the health, and gain a better understanding of, the headwater streams and waterbodies found in the Chiltern hills. Read on for a summary by Allen Beechey from the Chilterns Chalk Streams Project of the WIDL project and what is happening currently …..

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Background

The Chilterns is a predominantly dry landscape. Apart from the eight major chalk streams that rise within the chalk hills and flow through this area of natural beauty to the Thames and Colne there is very little freshwater habitat. However, a take a closer look at the foot of the northern scarp of the Chiltern Hills and you will find a number of tiny chalk streams which flow out into the Vale of Aylesbury and Oxford.  These headwaters are historically important, being the focal point around which many of the towns and villages along the foot of the scarp, were built.  However, very little is known about their importance from a wildlife perspective, or their influence on the southern reaches of the River Thame catchment into which they flow.

As part of the Chilterns Conservation board’s £2.4 Million pound National Lottery Heritage Funded, Landscape Partnership Scheme, Chalk Cherries and Chairs, a new project called Water in a Dry Landscape has been launched this year to find out more about the health of these streams. Jointly led by the Chilterns Chalk Streams Project (CCSP) and the River Thame Conservation Trust (RTCT) and working in partnership with the Freshwater Habitats Trust and the Environment Agency, the project aims to: identify, map and quantify the biodiversity value of headwater streams and other freshwater habitats;  engage and enthuse riparian landowners to develop catchment connections along the foot of the Chilterns escarpment; and to deliver riparian habitat creation, restoration and management projects.

Project timetable and detail

The first two phases of the project are being led by the CCSP and focus on survey and monitoring work to determine the condition of the headwaters stretching between Wendover and Aston Rowant.  Phase 1 began this spring with 15 volunteers being recruited to carry out initial water quality monitoring work at over 40 locations along the streams.  Four survey training workshops were held over the summer and the volunteers began monitoring in the Autumn and have now completed the first round of monitoring. A further three monitoring rounds will be carried out over the coming months to gain a detailed picture of the flow characteristics of the streams and the quality of the water flowing in them.

The data being collected will be used to check for any potential pollution issues and enable the project’s partners to identify areas that may require more detailed monitoring during phase 2.  Phase 2 of the project, will begin next year and will focus on detailed ecological surveys of shortlisted streams to find out more about habitat quality and the wildlife that they support.  This work will enable us to identify issues impacting the health of the streams and opportunities for habitat enhancement or restoration.

Phase 3 of the project will be led by the Landscape Partnership Landowner Engagement Officer team in partnership with CCSP and the RTCT and will focus on delivery of the projects identified in phase 2

To find out more about the Project visit the Chalk Cherries and Chairs Project web pages https://www.chilternsaonb.org/projects/CCC.html 

 


 

 

Riverfly monitoring – training event

On October 26th four volunteers joined us to be trained in Riverfly monitoring.

Riverfly monitoring is a great way to keep an eye on the health of your local watercourse and can help identify pollution issues.

A good time was had by all and we now have 21 sites actively being surveyed across the Thame catchment every month!

If you are interested in becoming a trained Riverly monitor then contact Hannah@riverthame.org


Dates for your diary

Celebration event and yearly review

We are excited to be able to invite you to our annual celebratory event. Come along and hear what we’ve been up to this past year (it’s been a busy one), celebrate all the wonderful volunteers that have made so much possible and hear an update on the catchment survey network results.

6:30pm on 9th December

Chearsley Village Hall

We will be raising a glass, eating some nibbles and taking a look back over the past year and all that has been achieved by our staff and wonderful volunteers.

We would be delighted to have you with us and hope you can attend

If you are interested in attending please sign up here so we can gauge numbers to cater for!


 

Watlington Environmental Group – A review and look ahead

Watlington Town Hall on Friday November 29th at 8pm

Watlington Environment Group began a Watercourses Project in 2013, with the aim of better understanding, protecting and enhancing the town’s streams, ponds and springs. Watlington is located at the source of the Chalgrove Brook in South Oxfordshire, which feeds into the Thame at Chiselhampton, and for its first few miles has the characteristics of a chalk stream. Watlington itself has a small population of brown trout, albeit a rather vulnerable one.

Over its six years, the project has gained a good understanding of how the seasonal and year-to-year fluctuations in flow are governed; delivered or facilitated significant habitat enhancements in conjunction with the RTCT, EA and others; sought to reduce the threats to the stream environment from carelessness and abuse; and generally raised awareness of this overlooked precious resource on our doorstep.

A talk in Watlington Town Hall on Friday November 29th at 8pm will summarise the findings and achievements so far – the highs and the lows – and set out some ideas for the future. Some initiatives further downstream will also be mentioned, and the talk may just provide ideas and inspiration for other communities across the catchment to begin their own projects.

All welcome, admission £3 for non-members. More details at www.watlington-environment-group.org.uk