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E
The River Crouch at Wickford Memorial Park is a high priority waterbody that is currently
failing to achieve its Water Framework Directive (WFD) objectives for hydromorphology. In
addition, the river is failing for a number of water quality elements including dissolved oxygen
and phosphates. Following a pollution incident in 2009 and the subsequent court case, Anglian
Water Services (AWS) volunteered to commit funding of £15,000 for a restoration project on
the stretch of the Crouch immediately downstream of the Memorial Park Bridge. The
principle aim of this project was to improve the ecology of the River Crouch at Wickford by
employing targeted, low-cost river restoration techniques. More broadly, the project has helped
fulfil the objectives of the WFD by focusing on those quality elements for which it is currently
failing.
The project involved the installation of several large woody-debris flow deflectors. Because of the high flood risk nature of the upstream town of Wickford, particular care was given to the stability of the features created. A belt and braces approach to the project ensured ecological gains without compromising the flood-risk function of the River Crouch. +
R
The River Darent in the Dartford area has been heavily modified over many years,including changes to channel planform, the implementation of land drainage schemes and abstraction,leading to an over widened channel. Prior to restoration this
section of river, two miles upstream of Dartford, was very uniform with a shallow gradient and uniform cross section. The natural substrate is dominated by pebbles and gravel but had become overlain by silt. Flow and habitat diversity was limited with
negative impacts on fish and macroinvertebrate communities. The aim of the project was to demonstrate that the processes that sustain a healthy chalk stream could be restored and the habitat protected during drought periods. This was to be achieved in a cost-effective way by re-working the in-channel gravels to form a low flow channel. The restoration work contributed to Chalk Rivers Biodiversity Action Plan (BAP) targets and complemented the implementation of the Darent Action Plan (1992).
All of the bed modifications were carried out from within the channel, so the banks and trees were left untouched. The channel was re-profiled using a long reach excavator creating a sinuous channel, with pool and riffle sequences, still within
the confines of the original channel. The excavator accessed the river where there were suitable gaps between trees and the creation of gravel berms at these points enabled the excavator to exit the river without damaging the banks.
A low flow channel was created by moving small amounts of gravel in a meandering path within the confines of the wider channel. Part of the bed was kept at a higher elevation to create a sequence of riffles. In other areas more significant quantities of gravel were redistributed enabling pools to be created. Pools, spaced at approximately 20m intervals, were designed to be self-cleaning. Gravels were placed upstream of each to narrow the flow and increase velocity to induce scour in the pools.
The whole of the construction phase was supervised by the designer who was on site throughout the work and provided instructions to the excavator driver.
Existing bankside trees with large root systems acted as natural deflectors and provided a variety of marginal habitat. A small amount of planting was carried out, including water crowfoot which was sourced locally from the Darent.
L
The River Darent is a tributary of the River Thames. This groundwater fed chalk river exhibits typical attributes including clear water, abundant macrophytes, low banks and reasonably stable flows.
The river has suffered from over abstraction as well as being heavily modified for historical agricultural irrigation and to provide power for milling. The rivers course through a number of large lakes fragment habitats and puts pressure on water quality and quantity in the river.
The North West Kent Countryside Partnership (NWKCP) and King Fisher Angling and Preservation Society (KAPS)carried out a project in 2010/2011 on the Darent running through the grounds of Lullingstone Castle. The Wild Trout Trust undertook an advisory visit in July 2009 to identify the project area which exhibited historical straightening, slow flows and high water temperatures due to its location just downstream of a 15ha on-line lake. Heavy siltation in the channel and dense wooded banks also contributed to an overall poor habitat for fish (particularly native Brown Trout).
Objectives included:
• Improve in stream habitat for juvenile and adult fish as well as provision of spawning habitats by the creation of areas of clean loose gravels and increased flow rates
• Increased flow levels to ensure a healthy flow to maintain habitats even during summer low flows
• Increase marginal habitats by clearing trees and scrub and planting new marginal aquatic plants to support invertebrate, wildfowl and water vole populations
• Narrowing and meandering of the channel using large woody debris and faggots
• Increase fishing opportunities by improving condition of the river
The Environment Agency initiated the project, with the North West Kent Countryside Partnership engaging with local fishing clubs who had initially developed and planned the project to provide advice and support work delivery. This partnership ensured the ability to deliver a wide range of objectives.
Project delivery was between January and April 2011 (to correspond with the closed fishing season) by KAPS and NWKCP staff and volunteers. The Environment Agency funded the £3,640 cost including materials and NWKCP officer time.
The reach was divided into sections A-F a brief review of work completed is:
A- Installation of deflector
B- Channel narrowing, faggoting to encourage new bank development and increase marginal habitat
C- Faggot barrier to block inlet, installation of coir rolls between faggot bundles to create vegetation
D- Block off artificial channels by installing faggots, planting area using coir pallets
E- Installation of large woody debris and coir rolls to narrow channel
F- Group deflectors at varying lengths, pack faggot bundles between deflectors to create marginal habitats
These works have been a success, making a noticeable difference to fishing quality (reports of increased catch rates). A reach has now been created which provides a variety of habitats beneficial to fish, and has encouraged possible spawning activity in the area. The KAPS and NWKCP are keen to continue works and have begun identification of possible sites for the future.
Since 2011 the North West Kent Countryside Partnership have revisited the project to deliver additional habitat improvement works. The additional work undertaken included the installation of large woody debris to create a set of 'v' deflectors which have established another pool and riffle sequence and helped to increase the flow within this location. The work provides additional spawning opportunity for fish as well as offering greater diversity in the types of habitat available.
The Partnership has also modified an overly wide canalised section (area F) to increase the depth and the flow rate through this section. The narrowing has also improved the scouring effect of the existing deflectors, helping to remove the heavy silt on the river bed and expose the gravels.
The RRC would like to thank Louise Smith (North West Kent Countryside Partnership) for providing all project information, site map and pictures.
H
The River Deerness catchment has multiple WFD failures, for both fish and water quality. Funding from the Catchment Restoration Fund as well as Durham County Council and Durham University allowed for the provision of a rock pool fish easement at a road culvert on at Cornsay Colliery located on Hedleyhope Burn (a tributary of the River Deerness), completed in September 2012.
Hedleyhope Burn is 9.2km in length. The road culvert has been cutting of fish access to 5km of good quality habitat, as under most flow conditions the culvert becomes impassable. This 30m corrugated steel pipe has rapid and shallow uniform flows when water levels are low, and concentrated high velocity flows at high water levels. An extensive erosion pool at the downstream exit to the culvert exhibits the force of water leaving the culvert. A wide concrete step 15 to 20 cm above the surface of the water also obstructs fish passage into the culvert.
The solution was to replace the existing scour pool with a series of rock pools to provide a variety of flows for fish, as well as drowning out the concrete step by increasing water levels back into the culvert and creating a slower and deeper flow, improving fish passage. Flood risk was not increased as the site is in a deep depression with no buildings close by.
The site is owned by Durham County who also contributed half of the cost. The Wear Rivers Trust helped with the design of the rock pool easement. Due to the location in a high rainfall upland area, 2-3 tonne rocks were used to form a continuous line of bank protection to protect the site a high flow levels. Larger gravels were also used, and willow spiling is due to be installed at a later stage. +
R
The River Don restoration project was initiated after the River Don was identified as a priority area for work by the Tyne Catchment Partnership. The waterbody is failing for Water Framework Directive and there are a number of large scale developments planned within the catchment which offered and opportunity for restoration.
The Don Catchment Partnership was set up in 2016, when a partnership vision for the Don was prepared. In 2016 when a need for a vision was identified there were 3 main areas of focus which were ‘water quality’, ‘flood risk’ and ‘Geomorphology/Ecology’. The need for a river restoration project which could encompass all 3 of these elements provided the basis of the vision.
In 2017 the River Restoration Centre were commissioned via a partnership project to develop a proposed River Restoration design for the Don. In addition to the Wild Trout Trust developed a report to identify issues relating to fish passage.
The River Restoration proposals have since been used to influence Highways England and the Planning Inspectorate for a major upgrade to the A19. As a result of this Highways England have allocated £950,000 to river restoration, which is due to be delivered.
The proposals have been used to influence a major development known as the ‘Follingsby Enterprise Zone’ which has the focus of developing economic growth. The project team worked closely with 3 Local Authorities to develop policies in the local plan which was used to safeguard a 50m strip either side of the River for river restoration purposes. This has now been embedded as a condition within the planning application for this site, thus delivering 11km of River Restoration.
The proposals have also been used to influence a major development known as the ‘International Advanced Manufacturing Park’ (IAMP). This is a nationally significant infrastructure project which is located in a greenbelt. The project team worked with Local Authorities and the planning inspector to embed river restoration into the Development Consent Order successfully.
In addition to the above the Environment Agency has been working with the Don Catchment Partnership to deliver land management campaigns, improving fish passage and reducing misconnections within the catchment to address WFD failures for Fish Passage, Phosphate, and Heavily Modified Status.
The holistic approach to River Restoration has been used as an example in the Catchment Based Approach (CABA) urban water management workshop as well as in the ‘Water Hub’ which is looking at innovative approaches to river restoration working with Small and Medium Enterprises (SME’s).
The River Dulais (Afon Dulais) is a tributary of the River Towy, and is an important spawning habitat for migratory fish. The river had a history of instability and planform adjustment. Unrestricted grazing, by sheep and cattle, had resulted in a loss of bankside vegetation. 4.9 km of the catchment had been fenced, however some areas needed more extensive bank protection.
Root wads were installed into the bank as an alternative to blockstone. In areas where the channel had additional capacity to scour or degrade brushwood protection was also used in between root wads. Careful thought was given to creating a smooth profile along the bank to reduce the risk of erosion. The riverbank above each root wad was protected by erosion control matting.
Forty root wads were installed over eighty metres of bank, with two to three metres of trunk left attached to the root wad. Crack willow (Salix fragilis), grey willow (Salix cinerea) and white willow (Salix alba) with an average trunk diameter of between 30cm and 60cm were used. Live willow was chosen as each tree should root and shoot to quickly bind the surrounding bank. All trees were sourced from within the Dulais catchment and two adjacent river valleys.
Since installation stabilisation of a complex outer meander bend has been achieved and each of the root wads installed has grown well. +
The River Eden River Restoration Strategy (RERRS) is a partnership project involving Eden Rivers Trust, the Environment Agency and Natural England, working with land owners and farmers. It aims to return rivers in the Eden catchment to a more natural state for the benefit of wildlife and people. It was developed as a remedy for the unfavourable condition of large parts of the River Eden and Tributaries Site of Special Scientific Interest.
On the River Lyvennet and Howe Beck at Barnskew and Meaburn Hall, Maulds Meaburn the rivers were restored to their original winding channels with approximately 1500 m of straightened river now meandering through nearly 1900 m. The project was undertaken in 2014 and an estimated 11,000 cubic metres of soil weighing approximately 15,000 metric tonnes was excavated. Very soon after the Lyvennet was diverted into its new channel, salmon were seen spawning in the river where they had not been seen spawning before. The site is a demonstrations of river restoration techniques and the many benefits this approach can bring to wildlife and people. +
The River Eden River Restoration Strategy (RERRS) is a partnership project involving Eden Rivers Trust, the Environment Agency and Natural England, working with land owners and farmers. It aims to return rivers in the Eden catchment to a more natural state for the benefit of wildlife and people. It was developed as a remedy for the unfavourable condition of large parts of the River Eden and Tributaries Site of Special Scientific Interest.
A straightened section of the River Leith at Thrimby Hall near Penrith was returned to its original meandering course with about 280 m of straightened channel now being 0ver 350 m long. This site is a demonstration of river restoration techniques and the many benefits that this approach can bring to wildlife and people. +
P
The River Ehen, supports the largest viable population of pearl mussels left in England, estimated at between 350,000 and 500,000 individuals. The Ehen is the most important river in England for freshwater pearl mussels, both biogeographically and for its size and population structure. 13km of the main River Ehen, from the outlet of Ennerdale Water, to the confluence of the River Keekle in Cleator Moor are designated as protected sites for both pearl mussels and Atlantic Salmon.
Pearls in Peril has delivered actions that work to reduce diffuse pollution, siltation and erosion and aim to improve water quality to safeguard the future of the River Ehen freshwater pearl mussel population.
The project has produced a river wide Conservation Management Plan that, for the first time, brought together stakeholders across the catchment to identify key issues and priorities. Directed by the Management Plan and supported by project partners the project has completed over 240m of willow spiling, fenced livestock from 5km of riverbank, provided alternative livestock waterings and planted over 7000 trees. Five sites, covering 350m of riverbank, have been restored using green engineering techniques including bank re-profiling, tree planting, willow spiling, and fencing. In-river obstructions causing erosion and scour have been removed and brash bundles have been used to encourage natural river bank restoration. Gateways and heavily poached stock crossings have been gravelled and the project has removed 60 tonnes of rubble from riverbank. Artificial bankside encystment of Atlantic Salmon was also carried out.
Volunteers have undertaken incredible amounts of work including hedge laying, making brash bundles, installing leaky dams, creating new wetland areas and tree planting. +
W
The River Ericht is part of the wider Tay catchment and has a steep, flashy catchment with an area of 432km2 to its confluence with the River Isla which later joins the River Tay. The project was located 2km downstream of Blairgowrie, Scotland and located within a Special Area of Conservation (SAC), UK0030312. The project was undertaken on a historic landfill site on the south riverbank of the River Ericht. There is considerable ecological variety in the Tay catchment, resulting in the Tay supporting the full range of salmon life-history types found in Scotland, with adult salmon entering the River Tay throughout the year to spawn in different parts of the catchment. In addition, Otter, Beaver, Bird and three Lamprey species (Sea, Brook and River) were found within the SAC.
The project consisted of landfill and riverbank remediation work. Landfill material was polluting the River Ericht impacting the watercourse and subsequent SAC following numerous spate events in 2015/16. This had a direct impact upon the ecology and environment. The aim of the project was to prevent further landfill material entering the watercourse and to install protective measures to protect the riverbank and reduce further erosion.
The project consisted of excavating 1800m3 of earth equating to approximately 3000 tonnes. The earth was put into a trommel where the landfill material was separated from the earth. The clean earth was used to re-profile the embankment and the landfill material sent to a recycling centre. The waste generated was approx. 50 tonnes; upwards of 97% was recycled. The waste consisted of timber, plastic, metal and green waste. Timber was shredded and used fuel (100% diverted from landfill), green waste was put into anaerobic digestion and turned into electricity and/or mixed with food waste to make compost (100% diverted from landfill) and general waste was handpicked and recycled (approx. 97% - 100% diverted from landfill). This is well within the targets set out within Scotland’s Zero Waste Plan which aims at 70% waste to be recycled and maximum 5% to landfill by 2025.
A number of non-structural green measures were implemented to stabilise the riverbank and reduce erosion. These include root wads, coir matting, planting live willow and sowing grass seed. A number of trees were removed as part of the site clearance process. These were set aside and later installed as and installed into the embankment and anchored with rock armour. Root wads were installed from upstream to downstream and spaced along riverbank at 5m intervals.
Root wads were installed on the outer bend of the River Ericht; this will help to absorb and distribute the energy from the river, reducing the erosive potential. Scour pools are predicted to form at the base of the root wad which can lead to reduced flow velocities enabling bankside habitats to form. Variation of the watercourse will increase by changing the temperature and oxygen levels across its cross sectional area. The creation of riffles, pools and shaded areas benefit the macro-invertebrate population and help to improve water quality, vital for maintaining the interaction of species protected within the SAC.
The new embankment was installed with biodegradable coir matting; this increases surface cover and generates roughness, key properties in controlling soil erosion. The coir matting was anchored to the embankment using FSC (sustainably sourced) timber stakes. A hedgerow grass seed mix was sown into the coir matting; this provides a diverse plant assemblage (native grass & wildflower) promoting plant diversity. This attracts insects and invertebrates including bees and butterflies; a step to provide habitats for species which are in national decline due to habitat loss. This supports the action plan set out in the Tayside Local Biodiversity Action Plan (2016-2026).
Live Osier willow was planted at 1m2 intervals, this introduces a root network which will help to stabilise the embankment. Willow provides habitat for flora and fauna, creating shading of riverbanks and spawning areas. Willow also promotes bank stabilisation, protects the aquatic environment from polluted surface runoff and improves soil chemistry by increasing humus formation. Fourteen trees were removed as part of the site clearance. As part of my sustainable environmental approach, I replanted twenty trees to replace the habitats lost and achieve net biodiversity gain. Hawthorn and Crab Apple were planted; this benefits pollinators such as honey, bumble and solitary bee species, together with moths and butterflies. Fruits are eaten by birds and mammal and are an important resource for migrant birds. A recent review of UK biodiversity (Natural Ecosystem Assessment) states that 40% of our most important habitats and 30% of rarest species are still in decline.
E
The River Evenlode, a headwater tributary in the Thames Basin (Map 1), is a flashy clay catchment with several small rural towns and villages prone to flooding. The Environment Agency is working with the Evenlode Catchment Partnership and local communities to develop and coordinate a 5-year project that integrates Water Framework Directive (WFD) objectives with a Natural Flood Management (NFM) demonstration scheme. The natural solutions to manage floodwaters often require land management changes to slow and store run-off, which can have multiple benefits for water quality and habitat creation, and drive improvements in agricultural land management.
In Year 1 of the project, a tributary catchment (16.3km2) trial in Littlestock Brook was set up with key landowners and the Parish Council. Opportunity mapping, site walkovers and modelling are being used to plan and implement a suite of NFM/WFD measures such as creating temporary water retention ponds in field corners, constructing bunds and scrapes to store more floodwater on grassland areas, installing woody material in-channel to create leaky dams, and land management changes including planting woodland in flood source areas and along flood pathways.
A project officer employed by the Evenlode Catchment Partnership in 2017 will work with partners to implement NFM and WFD opportunities across the 180km2 Upper Evenlode catchment. A key objective is to ensure full integration with Thames Water’s phosphate reduction project and Natural England’s Catchment Sensitive Farming initiative if opportunity mapping directs the project to work in the same tributaries of the Evenlode.
The results from this first NFM trial in the Thames Basin will contribute to the call nationally for evidence on the effectiveness of natural measures for flood risk in lowland catchments. Through an academic partnership a river level and turbidity monitoring network has been installed in Littlestock Brook. The plan is to engage the community to actively support this monitoring network. A key objective of this project is to determine whether multiple small-scale NFM interventions in these catchments can provide a material benefit to flood frequency and extent.
For these natural solutions to be successful, it is crucial to empower the community in decision-making and for them to take ownership of the local solutions employed. Employing an NFM project officer to work with the Evenlode Catchment Partnership is fulfilling Defra's ambition to develop community driven, catchment-based solutions to environmental issues through the forum of catchment partnerships.
G
The River Gade, a globally rare chalk stream with poor ecological status within Gadebridge park, used to flow down a ‘perched’ channel created to supply water to Bury Mill. It was disconnected from its floodplain and over widened, leading to sluggish flows and a build-up of silt and vegetation. The EA Gauging Station Bury Mill and other in-channel structures acted as barriers to fish movement. Being disconnected from groundwater and spring flow had a significant impact on low flow resilience and to wildlife. Partnered with Dacorum Borough Council and Affinity Water Limited, this Environment Agency lead project diverted 415 metres of river channel to the valley bottom through the park. The Bury Mill gauging station was replaced with an ultrasonic one to allow fish passage. Work progressed from 2018 with construction complete in June 2025.
0.85 hectares of habitat was created, 3.9 hectares habitat enhanced, 6.5 km of river restored, 0.9 hectares buffer strip created and 1.1km water body opened to fish passage. The river corridor now provides better resilience to low and high flows and the impacts of climate change. Two new bridges and a large gravel access point to the channel were provided for the local community.
The project was designed by JBA Consulting Limited and delivered by BAM Nuttall Limited. +
R
The River Glaven in north Norfolk has been historically modified, for example, through the creation of water mills. Coupled with this, widespread dredging has occurred and flood embankments have been created to protect agricultural land. The project's objectives were to improve the river corridor habitat by restoring river processes and reconnect the river and its floodplain and to develop an experience base that would serve the River Glaven Conservation Group (RGCG) well on other projects. The project provides a unique opportunity to monitor and model river and floodplain interactions. A MIKE SHE/MIKE 11 coupled hydrological/hydraulic model was employed to assess the impact of floodplain reconnection. Using data from 2007 to 2010, the study found that the removal of the embankment permitted widespread inundation of the floodplain at high flows (>1.7m3s-1) as well as enhancing flooding of the immediate riparian area during lower magnitude events. Removal of embankments has found to have reduced the channel capacity by approximately 60%, suggesting that overbank flooding was the most dramatic hydrological effect following the restoration project (Clilverd et al. 2013). +
H
The River Glaven is a chalk stream in North Norfolk. The project is on stretch of the river that was made wider by dredging about four years ago. These works will help the river to recover its natural state, enhancing habitat and improving its ecological status. +
The River Harbourne flows through the village of Harbertonford, which has been flooded on 21 separate occasions over the past 60 years - of which 6 flood events occurred between 1998 and 2000. The catchment is highly 'flashy', with little warning for residents prior to a flood.
The Harbertonford Flood Alleviation Scheme was a joint project funded by DEFRA, the Environment Agency, South Hams District Council and Harbertonford Parish Council, costing £2.6 million. Its aim was to reduce the risk of flooding through the implementation of engineered flood alleviation solutions. A zoned clay-core embankment dam ('Palmer's Dam') with a 4.1 ha (150,000 cu m) reservoir storage area was constructed 2km upstream of Harbertonford, in conjunction with 600mm of bed level lowering and channel widening through Harbertonford to increase channel capacity (to accommodate flows up to 28 cumecs - 10 year flood. A flow control system was installed at the reservoir outlet to permit normal river flow, with automated flood control gates to throttle flows during a flood event. In addition, a flood defence wall was installed and surface drainage systems improved. Together, these measures were built to prevent flooding in Harbertonford up to a 1 in 40 year flood event.
On 7th July 2012, a 1 in 40 year flood event occurred and Palmer's Dam was overtopped for the first time since its construction. This resulted in the flooding of some properties in Harbertonford, however flooding was limited to a few lowlying homes and the flood peak was significantly delayed, giving increased warning time.
As part of the bed-lowering technique, a series of pool-riffle sequences were constructed within the channel through Harbertonford - a best practice approach for habitat enhancement, proposed by the River Restoration Centre (www.therrc.co.uk). These would provide both improved spawning habitat and habitat for adult fish.
Works included:
*Channel lowered by 600mm through Harbertonford using pool-riffle sequences, to increase channel capacity, to withstand 28 cumec flow (1:10 year event). Also widened in areas to further increase capacity. Two weirs lowered to minimise backwater effect (Crowdy Mill and Mill Leat).
*Zoned clay-core embankment dam constructed 2km US of Harbertonford, with 4.1 ha flood storage reservoir (150, 000 cu. metre capacity), capable of withstanding up to 1:40 year event.
*Flood wall installed along a portion of the river, through Harbertonford. Replaced earth bank. Surface drainage systems improved.
Community Involvement - Local primary school visited site during construction of dam and have continued to visit 'reservoir' site, to study ecological development.
R
The River Impiönjoki is a short river only 495 meters long and it flows from the Lake Impiönjärvi to the Lake Simonjärvi. The catchment area is 97,92 km2. The river bed is mainly sand and contains rocks and gravel. A big part of the river is marked as nature conservation area. The water quality in the river is good or very good.
The Centre for Economic Development, Transport and the Environment for Lapland restored three sections in the River. The restoration was made to improve the living conditions of the fish and other species. Rocks and gravel was placed to the river to make rapid areas more suitable for the trouts to reproduce. The aim of the retoration was to improve the living conditions of migratory fish and to make the river more nature-like and closer to its natural state. Trouts, grayling and macro invertebrates will benefit from the restoration and not only in the river but also in the nearby lakes. The rivers in the area are straightened for log floating since 1900 century. Also the natural state in the rivers are altered because of intense forestry and bog drainage.
The restoration plan was accepted 4.3.2011 and the work started immediately. The plan was restore six rivers in the area. The area is highly appreciated among the fly fishers and its very popular recreational area.
The restoration plan aimed to slow down the current and produce suitable nesting habitats for the trouts and shelter places for the juveniles. Also versatility to the river bed was improved by digging few wider areas. Gravel was brought approximately 40 m3 and placed to the river in several places bed to ensure the nesting habitats for the migratory fish. Before the restoration many stones were taken away from from the river and places a side of the river. All the stones that were piled up next to the river, and in the channel were used in the restoration work. Also the wooden particles were used during the retoration work in the channel to make more curves and veratility to the river flow.
Also in the section two the culvert that enabled the fish to migrate was alered with rocks and gravel so that the fish could travel upwards.
The lenght of the first restored area is 10 meters and the width is 8 in average. The total area that was restored was 100 m2. The second part was 650 meters long, width 5 meters and the area in total was 3 300 m2. The thirds section was 50 meters, width 6 meters and the area was 300 m2. The elevation variation between the areas is 1,43 meters.
The River Irwell Restoration Project plans to restore urban watercourses in an effort to achieve good ecological status for the watercourse. Such plans must be viewed against the considerable economic and physical constraints imposed on such rivers due to their setting, in particular the need to maintain or even enhance flood protection levels and to ensure infrastructure remains uncompromised. A restoration plan was developed for the heavily modified River Medlock at Clayton Vale and Philips Park, Manchester. The principal aims of the study were driven by opportunities to improve the hydromorphological and ecological status of the watercourse through naturalisation, working to develop a watercourse where the reinstated channel units function to temporarily store coarse sediment creating dynamic habitat within a restricted urban environment.
Known as the ‘Red River’ due to the brick lining along the study reach constructed in 1912, the present U-shaped 'flume' has created conditions with limited in-channel morphology (occasional berm top fine sediments) and flow diversity (a monotonous run due to the almost uniform width and depth along the reach). No significant sediment storage occurs, despite a strong coarse sediment supply, as a consequence of the unchanging steep gradient and immovable planform (the brick-lined banks have restricted any lateral movement of the watercourse locally) creating a uniform, high energy, transporting reach and preventing any sediment deposition on the channel bed. Under present flow conditions, the high velocities are considered to be a barrier to fish passage, due to velocities of >2m/s under low flow conditions and 3-4m/s during higher flow events within the channel.
The River Medlock at Clayton Vale and Philips Park is designated as a Heavily Modified Waterbody. At present the Water Framework Directive (WFD) defines the overall river status as Poor Ecological Potential, but with a target of reaching Good Ecological Potential by 2027. Restoration needed to be mindful of impacts locally, and upstream and downstream of Clayton Vale and Philips Park, including impacts on flood risk given the highly urbanised nature of the catchment. Removing the brick-lining and concrete base layer, without managing the steep gradient and high energy levels of the River Medlock could create uncontrolled destabilisation. Therefore, removal had be considered alongside morphological restoration and naturalisation through Clayton Vale and Philips Park to ensure a 'dynamically stable' restoration was implemented and that historic features lining the watercourse were not compromised.
Consultation throughout the restoration plan development highlighted the ‘stand-off’ between the objective of river naturalisation and the ‘need’ for stability. The River Medlock at Clayton Vale and Philips Park would be a dynamic, active single thread river if not constrained by the brick – lining flume. Upstream analogue features (including, rapids, riffles and pools) and hydraulic modelling were used to carefully design and size functional, dynamically ‘stable’ morphological features to manage the high energy system following removal of the concrete and brick lining. Engineering concerns remained over the potential for ongoing lateral erosion that could threaten local historic walls and public footpaths. Compromise was therefore necessary to satisfy the project board before works could be undertaken, however, the majority of the restoration objectives for naturalisation were approved and the results of the first stage of the project and initial river response is reported here.
C
The River Johnsbach, a tributary to the River Enns, was heavily regulated and deprived of biological and hydromorphological diversity. Of particular concern was the inability of fishes to overcome the high concrete structures and the spawning habitat shortage all along the river corridor.
Part of the LIFE+ multi-site project for the restoration of the River Enns and its surrounding ecosystems was delivered in the Johnsbach Brook. The works targeted a stretch of several kilometres, were bank reinforcement structures were take-off and the mouth of the river was ecologically enhanced (i.e. gravel banks, etc.).
Restoration outcomes are positive overall. In particular, fish are now able to migrate and greater habitat diversity significantly supports in-site species populations (i.e. Common sandpiper (Actitis hypoleucos)). However there is still a technical problem related with the adjustment of the river slope and the high steps imposed by old sills. There is a deficit of dynamic gravel resulting from the long-lasting excavation in the Johnsbach valle. Overtime, changing erosion processes as well as variable flooding will continually modify the site while the river network is regaining its natural functionality.
The River Restoration Centre would like to thank Daniel Kreiner from the Gesäuse National Park for providing the information and photographs for this case study. +
R
The River Keekle is a tributary of the River Ehen located around 3 kilometres east of Whitehaven, in West Cumbria. The river was heavily modified until the 1990s due to nearby coal mining. After mine spoil was buried across the site the river was lined with an HDPE plastic liner. This liner was failing and heavily degraded, posing a flood risk and potential catastrophic contamination issue for the Keekle, as well as the River Ehen which is a Site of Special Scientific Interest and a Special Area of Conservation. Research by the University of Salford showed the liner had been shedding 500kg of plastic particles per year since its installation.
There was also concern that the river would vertically erode through the clay cap installed below the liner and expose ground water potentially mixed with mine waste that was buried in the 1990s, allowing heavy metals and chemicals to leach into the Keekle and further downstream. Whilst all of the EA’s sampling of water quality currently proved there was no contamination across the site, if nothing was done to stop erosion, there was a real possibility of the Keekle exposing mine waste in the future.
The Upper Keekle was also failing under the Water Framework Directive classification as a habitat for fish due to mining-related modifications. The modifications include the liner, bed-check weirs that washed out during floods in the 1990s, erratic boulder locations and areas where the plastic has broken up, creating barriers to natural fish migration.
This project, over a two-year period (2019-2020) removed the entire extent of plastic lining, replacing with boulders, cobbles and gravels to naturalise the river. A total of 180 tonnes of plastic was eventually removed and recycled, whilst around 16,000 tonnes of stones were imported into the site and strategically placed throughout the 2.5km expanse of restored river. +
E
The River Kennet was the subject overviews by the Environment Agency and Natural England. These overviews revealed that the Kennet was in an unfavourable condition with respect to its SSSI designation. Problems included barriers to fish migration, of which there were 3 major and 1 minor. Barriers usually refer to weirs which completely block any way for fish and eels to get to their spawning grounds. Weirs can also prevent the conveyance of sediments throughout a reach. The water meadows surrounding the channel were also classified as being in 'poor' condition.
The project objectives were to:
*Achieve favourable condition for the length of the Kennet through the estate.
*Achieve favourable condition for the Kennet, Lambourn and water meadows on the estate.
*Increase hydrological connectivity between the river and floodplain.
*Remove barriers to fish migration.
*Improve wild trout numbers.
*Improve the overall water quality of the fishery.
The measures used to combat these issues included the introduction of 3,000 tonnes of gravel along the profile. This was to allow for the formation of natural features such as riffles. The channel was narrowed by 5m in places to also allow for natural flows and variations withinin the channel. To address the four barriers to migration, fish and eel passes were built. Trees were cut back to reduce the amount of shade and introduce more light into the channel.
At points along the reach the banks were lowered to promote flooding onto the wetlands. Parts of the wetlands were also excavated to provide a better environment for the wildlife on the wetlands. +