Habitat Restoration - Case Studies
 

Rural Sustainable Drainage Systems

Location: Avington, River Itchen, Hampshire
Completion Date: Spring 2017
Partners: Test & Itchen Catchment Partnership, Landowner and R J Bull contractors


Objectives
  • Prevent soil run-off being drained from track into the River Itchen
  • Provide simple solution for on-going maintenance
  • Ensure adequate capacity for use by heavy agricultural vehicles
Summary
Rural Sustainable Drainage Systems (SuDS) are not a new concept, but they are still not widespread in the rural environment and could present many opportunities for improving our management of water at source. They are a collection of physical structures, used to mimic natural processes in helping maintain and manage the provision of good water quality.
 
The Test & Itchen Catchment Partnership (TICP) have been utilising Rural SuDS as part of their Sediment Pathways Project. This case study, at Avington on the Itchen, is a recent example of the sorts of works being delivered through the project.
 
The issue at this site was sediment being washed from a private track way, onto a public road and into a road drain that is connected directly to the river. The solution has been to install a cross-drain on the track way to divert water into a historic reception pond. The cross-drain was created by cutting and breaking out a trench and installing prefabricated 6 metre ACO M200 multi-drain sections with a 200mm grill width. This was linked to the reception pond by laying 50 metres of 150mm pipe across the corner of the adjacent field.

The completed cross-drain will be monitored in winter 2017 and maintained by the landowner into the future. We would like to thank the Environment Agency and the landowner for helping fund the works and the contractors RJ Bull for delivering an excellent job.
  
      

 
  
Eel Pass Project - Itchen Navigation

Location: Itchen Navigation 
Completion date: Autumn 2016
Partners: WCSRT, Veolia, Environment Agency, riparian owners


Summary
In 2015 the waste management company, Veolia, commissioned the WCSRT to help them offset the impact of their Marchwood abstraction on eels. The project aims to help local eel populations by delivering works to improve eel passage on the rivers Test, Itchen and Meon.
 
The first phase of the project was focussed on identifying structures and inspecting them for potential difficulties in limiting free passage up and down stream. During this phase the Trust visited forty-three structures across the three river systems, assessing the passibility of each structure for eels and elvers.
 
Over spring and summer 2016, the Trust started to undertake phase two of the project, to install eel passes or, where possible, remove barriers at fifteen shortlisted structures. During autumn 2016, the Trust worked alongside the Environment Agency and Elver Engineering Limited to design, permit and install eel passes at a variety of different structures on all three rivers, with fourteen out of fifteen sites now completed. Work also included the removal of two structures on the River Dun.
 
One of the areas identified during phase one of the project, for having a number of problem structures was the Itchen Navigation.
 
The old navigation boasts excellent habitat for eels but there is a series of structures, typically found at points where the old lock systems for the waterway were historically located. In most cases these structures were causing major obstructions to the free passage of eels and, particularly, elvers on their upstream migration.
 
In total the Trust looked at nine such structures between Winchester and Eastleigh. Several of the structures on the Itchen Navigation are Environment Agency owned and so in a combined effort to improve eel passage for the entire course of the Itchen Navigation, the Environment Agency are seeking to address the eel passage issues at the structures in their ownership, enabling this project to focus on delivering improvements at the remaining, privately owned, structures.
 
The photos show some examples of eel passes that have been installed on the Itchen Navigation. All of the passes are gravity fed and are typically comprised of bristle brush material housed in prefabricated aluminium casing or plastic piping. The passes allow elvers, in particular, to navigate their way past structures where high current speeds, barriers or the absence of mossy, vegetated edges would otherwise make it difficult for clear passage up or down stream.

 
      
   
NatWest Syndicate Project

Location: Lockerley, River Dun, Hampshire
Completion Date: Autumn 2016
Partners: NatWest Fly-fishing Syndicate, Woodland Water & Gardens Ltd, Veolia, Environment Agency and Natural England

Objectives
  • Remove impoundments and improve flow conditions
  • Improve fish and eel passage
  • Improve habitat diversity and habitat structure for wild and stocked fish
  • Improve bank conditions and accessibility for angling
Summary
The Natwest Fly Fishing Association (NFFA) is undertaking a multi-year river restoration programme on the River Dun, near Lockerley in Hampshire. The project began in autumn 2016 with the removal of two weirs and has been supported by the WCSRT through our Eel Passage Project, which is funded by Veolia.
 
Following work undertaken downstream at Kimbridge earlier in the year, the removal of the two weirs on the NFFA water is another step towards free passage of eels and migratory fish along the River Dun and paves the way for proposed works up-stream in 2017 at Lockerley Mill and Holbury Mill.


There is evidence that parts of the channel have been historically dredged and re-aligned, causing increased channel width and depth and, in turn, reducing water velocity and promoting the deposition of fine silt and organic sand material (twigs and leaf litter), which has resulted in an ideal growing substrate for the problematic submerged plant species that dominate the fishery. The impounding effect of the two weirs had further reduced water velocity and increased deposition; consolidating the sluggish, canal-like flow pattern and vegetation community.

The restoration work was being carried out by Luke Kozak of Woodland Water & Gardens Limited. Having removed the weirs, Luke now intends to allow natural process to play out over the winter months before resuming with phase two of the project in spring 2017. During the next phase of work, Luke will seek to strategically narrow and re-energise the river with site-appropriate techniques, including the reintroduction of flint gravels, riffle creation, instillation of log berms and woody material deflectors.

 

    
Sediment Pathways Project – Valley Farm, Bourne Rivulet
 
Location: Valley Farm, Stoke, Andover
Completion date: Spring 2016
Partners: WCSRT, Test & Itchen Catchment Partnership, riparian owners
 
Summary
During spring 2016, the Test & Itchen Catchment Partnership (TICP) delivered a programme of works at 14 key sites across the catchment, through their Sediment Pathways Project. The aim of the project is to reduce the high levels of fine sediment entering watercourses in the catchment via roads, tracks and pathways.
 
Historically, excessive fine sediment input to rivers has been perceived as a diffuse pollution problem, which can be difficult to solve in river catchments. However, in many cases land run-off is channelled and actually enters rivers at discrete points. The TICP have focused on this as an opportunity to prevent excessive fine sediment entering the river channels by targeting those discrete points, complementing work taking place in the wider catchment to reduce the loss of fine sediment from land (such as through Catchment Sensitive Farming activity), and ‘plugging the gaps’ that cannot be tackled within the structure of such funding schemes.
 
The project has concentrated on two sub catchments, the Bourne Rivulet and the Cheriton Stream, in order to pilot an approach and assess whether it can be effectively replicated through the rest of the Test & Itchen Catchment.
 
The track at Valley Farm on the Bourne Rivulet is typical of a number of similar roads, tracks and pathways in the catchment that run directly down steep valley sides towards the river in the valley bottom.
 
The aerial image and the photo illustrate how this track and others like it act as pathways for the rapid transportation of fine sediment from surrounding land. In this case the track itself and the adjacent field, which was being cropped for maize, were the primary sources of the sediment load.
 
In order to prevent silty water being transported directly into the Bourne, two cross drains were installed on the track. The drains were constructed with concrete bull-nosed kerbs and connected to settlement ponds, which allow the track run-off to drain away whilst fine sediment is retained. Also, the farm has agreed to alter the cropping on the adjacent field, replacing maize with a long-term grass ley, reducing erosion risk.
 
The results of the suspended solid analysis show the effectiveness of these simple measures at a single site and demonstrate how targeted delivery of similar works at a catchment scale could make a significant contribution to mitigating sediment inputs into river systems.
 
  
Wilsford Cum Lake Leat Project

Location: Wilsford cum Lake, River Avon, Wiltshire
Completion Date: Autumn 2015
Partners: Environment Agency, Black & Veatch, Natural England, Piscatorial Society, riparian owners and local residents
 
Objectives
  • Resolve breach of main channel
  • Restore flow to Lake House carrier channel
  • Maintain amenity value of leat channel (for fisheries interest and residents)
  • Deliver Special Area of Conservation (SAC) and Site of Special Scientific Interest (SSSI) objectives
Summary 
During the 2014 winter floods the true left bank of the River Avon (now a man made high level carrier or leat) breached upstream of Lake Hatches at Wilsford cum Lake, near Salisbury in Wiltshire. The breach resulted in a dramatic change in flow conditions causing the majority of flow to bypass the hatches and run laterally to an adjacent lower level side stream.
 
The changes caused a significant loss of amenity to the local residents living along the leat and they were keen to see the breach repaired and the previous flow regime reinstated. However, Natural England and the Environment Agency also saw the apparent environmental benefits of the breach and were keen that it should be retained.
 
Conflicting views were resolved after discussion through a series of face-to-face meetings to reach consensus, leading to construction of the scheme in Autumn 2015. The group chaired by the Rivers Trust director, Dr Paul Jose, worked with engineering and environmental consultants Black and Veatch led by their chief geomorphologist Jane Moon and lead engineer Alex Hughes to design a scheme.

After careful consideration and discussion an appropriate approach was agreed. This improved the aesthetics of the leat for landowners, continued to maintain flows to an important downstream water garden; and importantly improved fish passage. The design met the requirements of statutory agencies in terms of achieving and enhancing the internationally designated environmental interest of the River Avon. Local contactors Five Rivers of Lower Woodford worked with AMCO to deliver the project. The contractors were also engaged by the Environment Agency to deliver environmental improvements downstream of the hatches making this the largest single project undertaken on the River Avon in 2015.
  

  
River Avon Severals Fishery Habitat Improvement Project

Location: Westover Farm, downstream of Castleman Trail, Ringwood, Hampshire
Installation Date: June 2013
Partners: Environment Agency, Natural England, Mr D. Goulding, Ringwood Angling Club and the Barbel Society 


Objectives
  • Improve habitat for juvenile Cyprinids
  • Improve instream habitat variety
  • Improve cover for all instream species to reduce the threat of predation
  • Reduce flood risk to Ringwood
Summary
Using 5 Rivers Contracting Ltd., WCSRT excavated six new fry bays into the banks of the Avon to provide back water habitat for juvenile coarse fish.

WCSRT also installed 21 upstream facing log deflectors, keyed into the bank, to scour new pool/riffle features into the relatively uniform and open river bed. Low-growing willows were also planted at the bankside-end of all log deflectors to combat bank erosion and to add much needed in-stream cover and habitat features on the river bank.

The lower end of Bickerley Stream and two Culverts under Castleman Public footpath were cleared as part of the project, improving the conveyance of flood waters across the site and away from Ringwood town centre.

Net sampling in the summer of 2014 showed large numbers of dace, chub, minnows and other species utilising the safety of the bays and some interesting new instream features developing due to the installation of the log deflectors.

  
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