River Restoration


River Dun: Holbury & Lockerley Fish Pass Improvement Project

Location: Holbury Mill and Lockerley Mill on the River Dun
Completion Date: Summer 2018
Partners: WCSRT, Environment Agency, Black & Veatch Ltd, riparian owners


Summary
Since 2015 WCSRT has been working in partnership with the EA and riparian owners to improve fish passage at Holbury and Lockerley mills located along the lower reaches of the River Dun. The project has involved hydraulic modelling and design work by the civil engineering company Black & Veatch Limited (B&V) with project management provided by the Trust. Final design drawings were completed toward the end of 2016, agreement by the EA National Fish Pass Panel was gained in February 2017 and further planning and formal consents were ascertained over the summer. The location of the two mills along the River Dun is shown on the map (top right). 

The River Dun is a tributary of the River Test, the latter of which is popularly regarded as being one of the finest chalk rivers in the world with its crystal clear spring water supporting a rich diversity of fish, mammal, bird, invertebrate and floral communities. A commonality of both the Test and the Dun is that they have been modified in many ways over time, resulting in multiple in-channel structures and braided channels, which impact on flow dynamics, morphology and the resultant river qualities, including fish passage. This situation is compounded by the abstraction of water from the Test (and neighbouring River Itchen) catchment for potable supply, supporting the growing urban conurbation of Southampton and wider Hampshire towns and villages (including the Isle of Wight).

The combination of in-channel obstructions, historic land drainage and channel modification works (parts of the Dun were canalised in the 1800s) and abstraction pressures mean that it is increasingly important to ensure that all efforts are made to improve the resilience of our rivers. This includes enhancing fish migration opportunities alongside river habitat improvement works to promote improved, stronger sustainable ‘wild fish’ populations within the wider Test and Itchen catchment. 

Much time and effort has been invested by the WCSRT and the EA alongside other key stakeholders to improve fish migration opportunities along the River Dun, with a number of small weirs having been removed and in-channel habitat improved. For example, the NatWest Flying Fishing Association’s reach immediately downstream of Lockerley Mill (see case study below) has worked with the EA to improve channel sinuosity by creating bankside berms as well as the removal of small weirs to better energise the flow regime and hence boost biodiversity potential. These works will complement and add to the sum of benefits gained from the Dun fish bypass improvement works at Holbury and Lockerley.

The fish bypass designs for both mills involve the modification of existing mill bypass streams and includes the construction of a Larinier, i.e. a ‘fish ladder’ that enables fish to navigate a steep gradient over a relatively short distance. This is required in part to accommodate the artificially raised water channels at both mill sites, enabling fish to move from a relatively ‘low’ bed level downstream of each mill to the much higher bed level immediately upstream of the mills. The photo (to the righ) shows the Larinier fish bypass that has been built at Lockerley Mill. Please note the eel pass structure secured to one side of the Larinier wall, which will enable eels of different sizes to navigate the Larinier.

Five Rivers Environmental Contracting Ltd won the contract to deliver the fish bypass improvement works for the Trust and have done a superb job. The works commenced in September 2017 and are mostly completed at both sites. 

Monitoring surveys and results

  • Invertebrate sampling on an enlarged side-channel of the River Dun four months after fish pass installation at Lockerley Mill. Despite the wintery weather in early March there are already signs of aquatic vegetation starting to grow. A high proportion of aquatic invertebrates live happily within and on the riverbed gravel and using the standard pondnet sampling technique for just 3 minutes. WCSRT have confirmed natural re-colonisation is well underway. Around 20 different invertebrate 'groups' were retrieved using the pondnet, including one species (Simulium noelleri) generally confined to lake outlets and possibly displaced from the upstream fishing lakes. For full report please visit this link




River Avon Restoration Project

Location: River Avon and its major tributaries (Wiltshire and Hampshire) 
Completion Date: Autumn 2017
Partners: Environment Agency, Natural England, Wiltshire Wildlife Trust, WCSRT, Wessex Water, Wiltshire Fishery Association, Hampshire & Isle of Wight Wildlife Trust



Summary
The River Avon Restoration Programme (RARP) was set up to restore the River Avon Special Area of Conservation (SAC) to a naturally functioning river system to meet the government’s obligations under the Water Framework and Habitats Directives.

The implementation of RARP is an ambitious project as it aims to restore the River Avon to a naturally functioning river that supports characteristic chalk stream habitats and wildlife. The objective is to strategically deliver natural-process based schemes that restore reaches of river that have been most damaged by past physical modifications.

In many places the channel has been straightened or moved to the edge of the floodplain to work mills or water meadows and there are now some 150 weirs and sluices on the river. It has also more recently been dredged for land drainage resulting in an over-wide and deepened channel and has been embanked in places.

A range of restoration methods have been used to restore the rivers natural geomorphology and processes. These include the removal, modification and bypassing of structures; re-alignment of the river through the centre of the floodplain; re-meandering the channel within its existing plan-form and much more.

The completion of Phase 1 is not the end point but a springboard for the next phases of restoration using the knowledge, experience and goodwill built up over the past ten years. A further programme of work is needed on the remaining 185km of river to fully realise a more naturally functioning river catchment, able to respond and adapt to climate change.

For full report, please visit this link

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 downstream.











 

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.

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
Completion 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 Five 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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