Bossington Test reborn…

Project background

In 2006 and 2010 Natural England (NE) confirmed that the river Test was failing its SSSI designation and was duly classified as being in ‘unfavourable condition’. An Environment Agency walkover survey followed in 2012, from ‘top to bottom’ of the river Test catchment, as part of its Test & Itchen river restoration strategy. Its purpose was to identify priority locations for restoration. All six of the Bossington estate reaches were subsequently prioritised due to a number of key criteria including historic weir structures providing a major impediment to natural flows, floodplain connectivity, fish passage, heavy sedimentation and the failure of key plant and invertebrate species such as Watercrowsfoot (Ranunculus Spp) and Baetid invertebrates.

During May 2012 Bossington estate approached chalk stream restoration specialist Simon Cain of Cain Bio-engineering Ltd. (CBE) to discuss these concerns about habitat deterioration. The company was subsequently commissioned to survey and prepare restoration designs for all six beats on behalf of the Bossington Estate/Environment Agency partnership, with a view to implementing those designs in a series of phased projects.

To date and in collaboration with EA’s Test & Itchen project officer, Heb Leman and Estate Trustee/Farm Manager William Buckley, Cain Bio-engineering has now delivered four of the six projects, the most recent being the ‘House & Home’ beat weir removal scheme. This project was the focus of the T&I’s guided river restoration tour on 17th October 2017. The tour provided visiting members with a unique opportunity to observe a major habitat restoration project in full swing. By popular request we are now reporting back to the members and other interested parties on ‘How we built it’. Our report follows the format of the guided tour brochure map distributed to members at T&I’s 2017 AGM and the up-dated ‘As-Built’ ‘ brochure map enclosed with the recent annual rivers report. The web report details key works undertaken at each of the eleven sites as seen on the map.

An additional 1st year anniversary brochure will be circulated following the members forthcoming return visit to the project site in mid-October 2018. This visit will provide a fascinating insight into the science of chalk stream restoration and an opportunity to observe first hand the extent of predicted enhancements to the chalk river ecosystem. All of the stakeholders will be in attendance to provide a running commentary together with Dr Nick Everall of Aquascience Ltd. Nick will be on hand to talk about his pre and post monitoring invertebrate study of the restoration site and to explain the key habitat features of the restored watercourse that are critical to the well-being of invertebrate species of interest to fly anglers. Due to the widespread interest generated by this project, Bossington Estate and the Test & Itchen Association have kindly offered a limited number of non-member visitor passes to this event. These will be available on a ‘first come, first serve’ basis.

All enquiries to Jacqui Williams at administrator@testanditchen.co.uk

We hope you enjoy reading about this ground-breaking project.

William Buckley, Bossington Trustee & Estate Manager had this to say:

“Yet another skilfully executed project from Simon Cain and his team at Cain Bio-Engineering.  Cain Bio-Engineering not only delivered everything we had hoped for but exceeded many of our expectations on the project. The partnership between Cain Bio-Engineering, the Environment Agency and Bossington Estate has now delivered three restoration projects in under five years. Two thirds of the River Test beats at Bossington have been returned to a favourable condition.  Special thanks to Simon Cain and Heb Leman from the EA for this amazing legacy to the Estate”

Heb Leman, of the Environment Agency had this to say:

“The Environment Agency through the ‘Test & Itchen River Restoration Strategy’ were delighted with the finished collaborative restoration at Bossington Estate in 2017. Thanks to the forward-thinking attitude of Bossington Estate, Cain Bio-engineering have been able to transform and return an impounded, canal like section of the River Test into a free flowing Chalk river as it deserves to be. Over time the increased velocities and light will encourage and provide perfect habitat for a variety of Chalk stream flora and fauna for the benefit of the SSSI and the estate”.

Project Brief

Project description: This is a ground-breaking, catchment-scale river restoration project on the middle Test, centred around the removal of a sizeable and historic double weir installation. Following its removal, an 800-metre length of degraded and sediment-filled chalk stream habitat was restored on the ‘House’ & ‘Home’ beats, up and downstream of the old weir location. The project included the restoration of a derelict 200m side channel to create a salmon & wild trout nursery on the world-renowned Bossington Estate trout fishery in the village of Houghton near Stockbridge, Hampshire. SO20 6LT

Historical impacts on the riverine environment: Understanding the historical context of these weirs and the associated environmental damage, was key to informing the solution. The legacy of sub-optimal flow impacts from weir impoundments dates to the mediaeval floated water meadow system, an ingenious irrigation system involving the passage of flowing river water over an intricate arrangement of ridges and furrows to enhance winter grass and hay production. The ‘drowning’ practice was finally abandoned during the early 20th Century. Whilst the original purpose and vintage of ‘Home weirs’ installation (and longevity of the now-defunct Bossington water meadow system) is surmised, the weirs and their impounded flows appear to have been adapted to power an early (Victorian?) hydropower-scheme and most recently – up until 2017- were used to divert elevated river flows into a ‘perched’ trout-rearing stew pond. Suffice to say, the profoundly detrimental impact of impounded, canal-like flows on the river habitat at this location, meant that both weirs and the stew pond had to go.

The following historical activities added further to the degradation at this location;

  • WWII Channel dredging for anti-tank defences and/or
  • Post-war bed dredging and lowering of the water table for arable farming and ‘improved’ lowland grazing.
  • ‘Bunding’ of the impounded (perched) watercourse to prevent inundation of its natural floodplain during high flows.
  • Habitat degradation associated with, sub-optimal flow velocities including deposition of a heavy sediment load and high Biochemical Oxygen Demand (BOD) resulting from algal blooms and Phosphate-related eutrophication.

Key work & services provided:

The Bossington Estate client requested a ‘Principle designer and Contractor’ service to include:

  • An initial consultancy site assessment, detailed Topographic survey and outline detailed design leading to;
  • Submission of Environmental Protection Regulation (EPR) consent documents and associated consultation with Environment Agency (EA)
  • Provision of consented detailed designs including Risk Assessments, Method Statement, Protected Species surveys and detailed cost analysis.
  • Project delivery – Including detailed site supervision, on-site technical direction and client reporting throughout the two-month project delivery period.
  • Post-project monitoring including assistance with planting operations – Bankside margins and instream Macrophyte ‘weeds’ – Water parsnip, Ranunculus, & Starwort.

Work/Solution

The key project objective was to return the linear, over-deep, impounded, slow-flowing and sediment-filled channel to a free-flowing state over a shallow, letterbox-shaped, gravel-bed profile. Following weir and silt removal, this was achieved by in-filling the dredged ‘U’-shaped cavity with ca. 4,000 tonnes of ‘as dug’ gravel to reinstate the 1:450m gradient through a series of meanders.  The new channel, with flows streaming down the enhanced gradient, was then spot-treated with ca.1,500 tonnes of gravel using a variety of techniques to create a varied bed morphology and to equitably distribute ‘fluvial energy’ between, around and over a series of inside-meander deflectors, pools, riffles, glides and ‘pocket’ water. These techniques are illustrated throughout the report.

For ease of reference the following description of ‘how we built it’ conforms to the route shown in the Test & Itchen Association’s site visitors guide below. Points 1 to 11 highlight key features of interest throughout the restoration site and provide a detailed insight into all aspects of works undertaken with images showing the river status before, during and immediately after project completion.

Fig 1. T&I project site map with key features of interest

We will be providing further detail on the 11 key features. To discover more about this extensive restoration project, click on the numbered highlighted features below;

  1. ‘House beat’ – R/H branch (Bossington mill race d/s to Wallop brook confluence)
  2. ‘House beat’ L/H branch – (Upper reach to top boundary)
  3. Gravel extraction site
  4. ‘House beat’ L/H branch (bottom reach to confluence)
  5. Pipe bridge crossing – Upper ‘House Beat’
  6. ‘House beat’ Central
  7. ‘Home beat’ U/S Weir pool & Fishing hut
  8. ‘Home Beat’ weir structures
  9. ‘Home beat’ D/S Weir pool & Riffle
  10. Nursery side stream
  11. ‘Home beat’ to Bailey bridge
  12. Ecological monitoring
  13. Native planting of margins and in-stream macrophytes

 

Team Profiles

William Buckley is the managing trustee for Bossington Estate and has run the Estate and fishery since 2010. The Estate has 2.5 miles of double bank fishing on the main River Test, comprising 7 beats, and 2 miles of the Wallop Brook tributary.  William recognised that remedial work was urgently needed to reverse historic impacts on the rivers ecology, fish habitat, morphology and hydrology to ensure that Bossington Estate would continue to offer the very best chalk stream fishing for generations to come. In 2011 William engaged Simon Cain of Cain Bio-Engineering to work with the Estate to undertake an assessment and restoration of all the Bossington Test beats. Work has now been completed on two thirds of the fishery following the recent removal of Home Beat’s double weir system. This, the most ambitious project to date, enabled the combined restoration of the adjoining House and Home beats, together with the creation of a dedicated 200m spawning and nursery stream for wild trout and salmon.

Heb Leman is the Test & Itchen (T&I) Restoration Strategy Project Officer for the local Environment Agency (EA) Fisheries, Biodiversity and Geomorphology Team based in Romsey. Heb has worked in T&I for over 20yrs, first as a Fisheries Officer, then as the Fisheries Technical Specialist and since 2012, as the Project Officer for the T&I Restoration Strategy, a joint initiative between the EA and Natural England (NE) with the aim of working collaboratively with land owners to restore the rivers Test and Itchen. The T&I SSSI’s are currently classified as being in unfavourable condition. The aim of the Strategy is to enhance, where necessary, the habitat in both rivers to encourage chalk stream flora and fauna to flourish so that both rivers can be classified as being in favourable condition. To date the Strategy has worked with over twenty owners for the benefit of these two world-famous chalk rivers. The ‘Home Beat’ weir removal and 800m river restoration at Test Bossington is EA & EN’s largest and most ambitious collaborative project to date.

Simon Cain is an award-winning aquatic bio-engineer and river restoration specialist who pioneered catchment-scale chalk stream restoration on the Hampshire Avon during the early 1980’s. Over the past 35 years his Hampshire-based company, Cain Bio-engineering, has delivered habitat-focussed projects on all the key chalk stream catchments including a 7 km restoration of the river Nar in Norfolk. Recent projects include the restoration of a failing dam, lake restoration and stream diversion for the Defence & National Rehabilitation Centre (DNRC), two extensive Mill leat systems with river habitat restorations on the river Itchen and large-scale inter-tidal sea defences using innovative sediment traps. Current projects include re-alignment of the river Mersey to protect threatened infrastructure for a national utility, and a major design and consultancy assignment for an international environmental agency in America. The Bossington weir project is his most notable contribution to the river Test restoration strategy to date.

Dr. Nick Everall did his doctorate in fisheries ecotoxicology at the University of Nottingham in early 80’s and was a Research Scientist on the Acid Rain Programme in the mid 80’s. He was Head Scientist at the Department of Agriculture and Fisheries for Scotland and the North East River Purification Board in the late 80’s including Head of The Pigmented Salmon Project. Nick was Principal Biologist for Severn Trent Water Limited in charge of all biological aspects of water treatment, drinking water supply, sewage treatment and environmental protection from 1990-2001. He established the  Aquascience partnership in 2001 involved in fisheries enhancement, algal control, laboratory services and environmental consultancy for wetlands. Nick established Aquascience Consultancy Limited in 2013 concentrating on laboratory services and aquatic environmental consultancy. He has published over 30 research papers on varying aspects of wetland fisheries monitoring, management and climate change. Nick and his team are UK leaders and developers of biomonitoring tools for assessing ecological condition and water quality status of standing and running waters.

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