Client: Defra Partners: JBA Consulting, National Trust, Environment Agency, Penny Anderson Associates, Wessex Water, Exeter University, National Trust tenant farmers Location: West Somerset, England Date/Phase: 2009-ongoing Funding sources: Defra, Environment Agency, National Trust Offline storage pond on Aller floodplain (with controlled pipe outlet)
PROJECT | From Source to Sea: The Holnicote Project The Holnicote Project is one of three multi-objective flood management demonstration projects commissioned in 2009 as a direct result of the recommendations from the Pitt Review of the Summer 2007 floods. These projects were all tasked with providing evidence to demonstrate how applying a Working with Natural Processes (WwNP) approach, to slow and store flood water in the landscape, can contribute to reducing flood risk to downstream receptors whilst also providing a range of other benefits to the environment and society. Two instrumented catchments on the NT Holnicote Estate – Horner Water (22km2) and the River Aller (18km2), a range of WwNP measures were implemented.
WwNP measures Following the application of a range of detailed monitoring, assessment, spatial analysis and modelling approaches across • Offline storage ponds and wetlands: Five shallow earth bunded flood meadow areas (with outlet control pipes) and some surface water scrapes have been created on the middle Aller floodplain to increase floodplain storage capacity. • Instream structures: Instream woody debris dams and accumulations have been installed to slow flows in the Horner headwaters; the development of natural in-stream debris dams has also been encouraged in the existing historic woodland (Horner Wood).
• Soil management practices: Tenant farmers across both
catchments have been advised on applying in-field soil management best practices in managed grassland and arable fields, including the use of a soil aerator in fields experiencing soil compaction. • Moorland runoff attenuation features: Surface runoff from the Horner headwaters has also been slowed and connectivity with the arterial drainage network has been reduced through the construction of 800 shallow earthen cross bunds along 20km of footpaths and tracks across the moorland. • Woodland creation/restoration: pockets of woodland have been created and wet woodland restored in the middle Aller catchment to intercept and slow floodwater, and improve infiltration of water into the soil profile. • Land use change: Reversion of arable land to grassland on moderately sloping ground in the Aller catchment to provide a more permanent and continuous vegetative surface that can slow surface runoff and/or improve inception and infiltration of direct rainfall.
Summary of Project Outcomes • Comparison of the basic characteristics of the ‘before
change’ flood hydrographs with the ‘after change’ flood hydrographs are showing evidence of lowering and
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flattening of the hydrograph shape and delay in the timing of the flood peak. No property flooding was experienced in the vulnerable villages during the very wet winter 2013/14 in Somerset when local residents reported that they had expected some flooding to take place. The combined effect of the five offline storage ponds (storing an additional 18,000m3 of floodwater) reduced the flood peak flow in the River Aller by 10% during the most severe flood event measured in winter 2013/14 (which had an estimated return period of in excess of 1 in 50 years). On-going, regular and sensitive engagement with catchment stakeholders and the local communities, through a trusted catchment advocate (NT Project Manager), including the provision of appropriate monetary and non-monetary incentives for change, has greatly helped the continuing success of the project. Sufficient time and resources are needed to explore and discuss WwNP aspirations with catchment stakeholders, and to engage with all the relevant regulatory authorities with respect to consents and approving the implementation of WwNP measures.
Modelled flood depths on Aller floodplain – pre and post-WwNP bund construction, severe Dec 2013 event
Reference A Summary Report on the findings of the Holnicote Project covering the period 2009-2015 can be found on the National Trust web site at: http://www.nationaltrust.org.uk/features/ living-with-change---managing-water-and-flooding.
Contact Steve Rose: steve.rose@jbaconsulting.com for more information see: LInk
Project Benefits • The development, upgrade and maintenance of this
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demonstration and research platform, with the invaluable support of the National Trust, is helping to influence, shape and encourage the wider uptake of the WwNP approach both regionally and nationally in the UK. A number of the spatial data analysis tools and hydrological/hydraulic modelling techniques developed and/or applied by JBA across the study catchments have been successfully transferred to several other WwNP initiatives in the UK. The Holnicote project continues to provide evidence on the impact of WwNP on downstream flood risk, together with the provision of multiple benefits to the environment and society, including: improvements to biodiversity, landscape quality, carbon stewardship, water quality, and amenity and recreation.
Moorland runoff attenuation features in Horner headwaters
Woody debris dam in Horner Wood
Schematic drawing of the Weir plan
PROJECT | Lowthorpe Weir JBA were commissioned by Natural England to identify and appraise options to improve the condition of the Hull Headwaters SSSI at Lowthorpe.
Background The headwaters of the River Hull are nationally important as the most northerly chalk stream system in Britain. Lowthorpe Beck is a tributary of the River Hull and part of the river’s headwaters. The river system is designated a Site of Special Scientific Interest (SSSI). Lowthorpe Beck has been modified at the site of a former mill at Lowthorpe village and this has had a negative effect on the habitat and morphology of the channel. Further upstream other changes to the watercourse have been made over time. It is these changes that have led to the SSSI being in ‘Unfavourable Condition’.
What we did The project was divided into three phases,
Options appraisal
(Phase 1)
Stakeholder engagement
Client, Stakeholders, Partners: Natural England, East Yorkshire Rivers Trust, local landowner and land managers. Location: Lowthorpe, Driffield, East Yorkshire Date/Phase: 2012 to 2015 Funding sources: Natural England, Environment Agency
Phase 1 was an options appraisal into the feasibility of removing the weir at Lowthorpe. This involved a detailed engineering inspection of the weir and races as well as ecological and archaeological survey and Landscape Visual Assessment of the preferred option. This was taken forward by Natural England and used in public and stakeholder consultations. Phase 2 was the detailed design of the preferred option, which involved the filling-in of the mill race, leaving the structure in-situ and bypassing through re-occupying the old channel of the Lowthorpe Beck. Then creating a new section to channel across a field to re-join the tail race channel upstream of a small bridge thereby avoiding the need to instruct a new bridge across the old beck channel.We did a detailed NVC ecology survey of the grasslands through which the new weir bypass channel as well as topographic survey and engineering design. Phase 3 was the construction of the new channel by the East Yorkshire Rivers Trust in 2015.
Summary of Project Outcomes The project removed a physical barrier from the SSSI,
Detailed design
(Phase 2)
Construction
(Phase 3)
allowing the river to re-occupy part of its former channel with the gravel bed still in-situ, creating a more natural planform and reconnecting it with its meanders and floodplain. The outcomes were: • Fully costed options appraisal of three main options with two variations; • Preliminary Ecological Assessment detailing the ecological benefits of each option; • Cultural Heritage Assessment of each of the options and variations; • Landscape Visual Assessment of the preferred option; • Presentation material for use in public engagement events; • Full detailed design taking into account the sensitivities of the site and the river; •
Partnership working and full stakeholder buy-in from the outset.
Project Benefits The archaeology has been left in-situ rather than destroyed. Natural England and the East Yorkshire Rivers Trust are very happy with the outcome and the baseline conditions in the new reach were recorded in detail allowing any change to be quantified in future surveys. Effective working between the project partners and the lessons learned on this weir have since been employed on other weirs elsewhere on the Hull system.
Lessons learned • Early stakeholder engagement is essential aswell as communication on progress. • Compromises can bring results and greater co-operation: this was demonstrated with the archaeology and the avoidance of having to construct a new bridge downstream.
Contact Kieran Sheehan: kieran.sheehan@jbaconsulting.com: or Matthew Hemsworth: matthew.hemsworth@jbaconsulting.com for more information see: LInk
Client, Stakeholders, Partners: Natural England; Environment Agency, Yorkshire Dales National Park Authority, National Trust, Yorkshire Dales Rivers Trust Location: Kettlewell, North Yorkshire Date/Phase: Feasibility Stage 2012 Key: Geomorphology, Stakeholder Engagement, Ecology, International Riparian Survey (IRiS), Phase 1Habitat Survey, River Typology, Morphology
PROJECT | Restoring the River Wharfe SSSI: A River Restoration Plan Background The River Wharfe is a nationally important river designated as a Special Site of Scientific Interest (SSSI) for its contrasting upland and lowland character important for its wildlife and habitat. The SSSI status covers the river channel and small areas of adjacent floodplain between Buckden and upstream of the River Skirfare confluence near Kettlewell. The River Wharfe is within the protected countryside of the Yorkshire Dales National Park important for its outstanding scenery, wildlife and cultural heritage.
What we did
Description
The morphology of the river was described and, on the basis of these results, the river was divided into a number of functional reaches for which we devised restoration measures.
The River Wharfe SSSI is currently in poor condition preventing the river from functioning naturally, reducing its ecological health and stopping the SSSI from reaching its potential. We were asked to produce an ecologically desirable vision for the River Wharfe SSSI that would be characteristic of the river without morphological restrictions. This involved developing a conceptual model of the current functioning of the river and floodplain now and in the future. This would form a draft river restoration plan for consultation with stakeholders.
We undertook an Integrated Riparian Survey (IRiS) of the Wharfe between Hubberholme and the confluence of the Wharfe with the Skirfare. This recorded the vegetation in the channel, margins and banks every 250 metres and mapped all invasive species and habitats present on the floodplain in Phase 1 Habitat format. In addition all geomorphological features in the river were target noted and any colonising vegetation surveyed.
Summary of Project Outcomes The project involved: •
The mapping of 10km of the floodplain to Phase 1 standard with target notes
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The mapping of all palaeo-features on the floodplain and their vegetation described
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The mapping of all the morphological features within and alongside the channel: these were also target noted and described and any vegetation present surveyed
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The identification of a number of morphological units were identified which were characterised and mapped.
Stakeholder engagement and public participation events were essential throughout this project. Allowing us to produce an outline ‘vision’ for the river, based on the specific recommendations for the functional reaches that we identified.
The Vision for the River Wharfe •
A dynamic and diverse river bed which is suitable for fish and invertebrates.
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Variable channel features with a variety of river depths and flow speeds.
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Varied bankside plant structure, including areas of shading and occasional open stretches of floodplain meadow.
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Diverse plant, invertebrate and breeding bird communities that are able to use the river corridor with minimal disturbance.
Lessons learnt
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Low levels of river engineering allowing natural movement of the channel within a narrow riparian strip.
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Eco-hydromorphology assessments are more productive in specialist teams
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Increased connection with the floodplain where wet grassland and meadows, fen, carr and wooded areas may develop.
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Enhance the landscape character’s natural beauty, diversity and setting of the river and its floodplain
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Consultation at an early stage in the process is desirable to ensure stakeholder and landowner buy-in and reduce any delays to the project
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Ensure ‘informal’ time is allowed for in public events to allow private discussion with individuals who are not prepared to speak in public
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Identification of key individuals who can help take the restoration project forward
Project Benefits The ‘vision’ for the river has led to a project board to be set up by the Yorkshire dales Rivers Trust. Their aim is to deliver some of the projects highlighted in the plan through working with farmers and landowners, including fisheries interests. The Trust has engaged volunteers in Himalayan balsam pulling, willow spiling and tree planting along the river. They are also seeking funding from project partners for larger-scale projects.
Contact Kieran Sheehan: kieran.sheehan@jbaconsulting.com or Matthew Hemsworth: matthew.hemsworth@jbaconsulting.com for more information see: Link
Client, Stakeholders, Partners: Natural England Location: River Teme SSSI Date/Phase: 2013 Key: River Restoration Plan, Geomorphology, Ecology, Fisheries, Water Framework Directive
PROJECT | River Teme Background Our geomorphologists, ecologists and fisheries experts developed a river restoration plan for the River Teme, a tributary of the River Severn which passes through Herefordshire, Shropshire and Worcestershire, with its headwaters in the Welsh borders. Natural England’s vision for the River Teme is to return it to a more natural condition by restoring the natural form and function of the river and its floodplain over the next 50 years. A total of 134 km of the River Teme was designated as an SSSI in 1996, of this 110 km flows in England together with approximately 5 km of the River Clun and this combined river length forms the study area for this project. The Rivers Teme and Clun support important populations of otter, Atlantic salmon, bullhead, grayling, twaite shad, brook lamprey, sea lamprey, and white-clawed crayfish and the lower reaches of the River Clun are of European importance for the populations of freshwater pearl mussel. The existing condition of the Teme is influenced by physicochemical, hydrological, biological and physical factors. The majority of the SSSI remains classified as ‘unfavourable recovering’ due primarily to physical system modification including:
• Weirs • Mills • Hydropower • Bridges • Deflectors • Revetment • Embankments • Invasive species and disease The overall aim of the project was to address physical habitat issues and devise an appropriate whole river restoration plan to be implemented on the ground. The river restoration plan was based on a detailed scientific understanding of the river and floodplain and set out a means to which the recovery of the SSSI could be achieved in the long term.
What we did? We conducted an integrated geomorphological analysis and ecological interpretation of physical impacts on the river. This involved auditing and surveying the complete length of the 130km river. • The ecological survey recorded habitats adjacent to both banks of the river following the standard Phase 1 Habitat Survey methodology.
• Aquatic macrophyte surveys were conducted along
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the full length of the river, with detailed spot check surveys undertaken every 500m, where access allowed. At each spot check site we recorded the species present within the river and sections of bank likely to be frequently inundated. Any other features of note were also recorded such as evidence of siltation, cattle poaching, fording, bankside modification or pollution.
Photographic records were compiled with photographs taken up and downstream and across the channel. During the walkover survey we also recorded any evidence of protected or notable species, in particular Otter and Badger. Any evidence of non-native invasive plant species was highlighted and Himalayan Balsam was found to be a particularly severe problem from the middle reaches to the confluence with the Severn. This led to a comprehensive map of non-native, invasive species being compiled for the whole river. The next steps 1. The results were used to generate an outline restoration plan for the river on a reach-by-reach basis 2. We identified the likely delivery mechanisms for different aspects of restoration and provided approximate costings 3. We assisted Natural England and partners in a consultation exercise with stakeholders 4. We produced a final restoration plan, incorporating the results of the consultation exercise
Summary of Project Outcomes The river restoration plan builds on an understanding of the morphology and ecology of the river and its floodplain and the relationship of this form with the processes controlling sediment and gravel redistribution along the system. The plan also takes into consideration existing constraints and land uses along the river when considering site based actions and implementation. Identification of key pressures along the River Teme: • Bed erosion, incision and floodplain disconnection • Bank instability • Embankments • Lack of trees and woodland • Poor floodplain management • Invasive species • Channel training and bank revetment • Channel realignment
Identification of restoration opportunities: • Floodplain reconnection • Introduction of riparian woodland • Wet woodland creation • Removal and setting back of embankments • Development of vegetated bars • Soft bank protection • Weir removal • Island development • Woody debris
Project Benefits Development of a river restoration plan which lays out a number of restoration options for the River Teme to be implemented over the next 50 years working with local river owners and managers.
Contact Kieran Sheehan: kieran.sheehan@jbaconsulting.com: or Matthew Hemsworth: matthew.hemsworth@jbaconsulting. com for more information see: LInk
Team approach to the development of the restoration plan and all the elements considered Historic influences
Historic influences
Catchment management
Catchment controls
Catchment controls Catchment management DESK BASED OVERVIEW
CATCHMENT CONTROLS
CONCEPTUAL WHOLE RIVER MODEL Vegetation communities
Flow regime Sediment regime Local management HYDROMORPHOLOGICAL & ECOLOGICAL ASSESSMENT
SSSI ECOLOGY
DRAFT RIVER RESTORATION PLAN
FLUVIAL FORM & DYNAMICS
Biotic modification
Options testing Consistent identification
LOCAL CONTROLS
Flood risk Economic viability CONSULTATION
FINAL RIVER RESTORATION PLAN
Flow hydraulics
Morphology
Channel & floodplain management