Supply Chain - Flood Alleviation

The Don Regulators comprise three regulator gates on the River Rother that are owned, operated, and maintained by the Environment Agency (EA). The purpose of the regulators is to reduce the risk of flooding to settlements within the River Don catchment by attenuating flows in the River Rother. JBA-Bentley has completed the design and installation of the first regulator gate. The detailed design of the second gate is currently being undertaken, while the third regulator is being modelled as part of the optioneering phase. In addition to the installation of the first regulator gate, a bespoke full-channel fish pass has been installed directly downstream to improve migratory fish passage.

The Meadowgate Regulator is located within the Rother Valley Country Park. The historic regulator consisted of a single fish belly bottom-hinged tilting gate, operated by a single electrically powered hydraulic ram.

In 2023, JBA-Bentley replaced the gate with a top-down vertical control gate, improving the resilience of the structure. Alongside the regulator gate, a new control building and EA Office have been constructed. Both buildings have green roofs and EV charging. The gate was commissioned in February 2024 and is ready to operate during a flood event.

The gate is operated to ensure a maximum of 60m3/s forward flow is always maintained. When flows exceed 60m3/s the new gate is lowered and water levels in the Rother rise and begin to spill into the washlands located within the Rother Valley Country Park, which can retain approximately 1.5 million m3.

The removal of the bottom tilting gate provided an opportunity to improve fish passage on the River Rother through the installation of a unique full-channel width fish pass. This fish pass is designed with 4-tonne reinforced concrete ‘fish tiles’ featuring varied-height upstands supplied by Craven Concrete Ltd.

The tiles were designed with the aid of computational fluid dynamics modelling to ensure they influenced the nature of the flow to allow for varied fish species to migrate upstream while also withstanding hydrodynamic forces during extreme events. The fish species focused on are coarse fish, European eels, brown trout, large migratory salmonids, and lamprey.

The 40m long stilling basin has been removed by building up the existing concrete channel bed and grading out the levels to create a uniform slope. The ‘fish tiles’ have been laid onto the regraded channel. This is the first fish pass of its kind in the world.

The fish pass installation required the full channel as a dry working area. To achieve this, an innovative syphon system, designed by Dutch water specialist Vanderkamp UK, was installed. The solution involved complex temporary works and contingency planning.

To form the upstream dam, the new regulator gate was dropped to bed level, allowing upstream water levels to build up. The gate was designed to operate this way; hence no further calculations were required. Four syphon intake pipes were installed upstream of the gate to divert up to 12m3/s of flow out of the channel for 115m, around the working area.

The syphons were primed using electric vacuum pumps which expelled all the air from the system to draw water through the pipes. By utilizing the existing gate and power supply, the syphons had a far lesser environmental impact than a typical cofferdam and over-pumping solution. The total embodied carbon associated with the syphon solution was 464 tons.

Due to the scale of the flows being diverted, the loads imposed on the riverbanks by the pipes when full were considerable. JBA-Bentley and Vanderkamp UK worked together to design a temporary support system involving ground-bearing improvements, steel and timber supports, and retaining structures. Checks were also carried out on the existing channel wall where the forces from the syphons acted upon it.

In addition to work to ensure the stability of the syphons, an energy dissipation system was designed and installed at the syphon outlets to combat scour, and a bubble curtain was installed upstream to deter fish from entering the syphons. The installation of the system was done via a temporary crane pad. Due to the nature of the site and its space constraints, this was a challenging design. JBAB worked closely with the landowner, Rother Valley Country Park, to balance the desire to allow continual access into the park with ensuring the crane was safe to carry out the required lifts. To achieve this, the crane had to be placed in close proximity to the riverbank. Slope stability modelling and bearing capacity calculations were undertaken to ensure the crane could be operated safely.

Recent storm events have recorded flows higher than the syphon capacity. To manage the risk of this occurring during the programmed works, a contingency plan was developed.

The basis of the plan was developed from a bespoke JBA flow forecasting system, which forecasted the flow over a 2-day period. Using the data from the forecasting system, flow monitoring data provided by Vanderkamp UK, upstream gauge data, and the storage capacity of the washlands upstream of the gate, JBAB could make informed decisions on whether the gate needed to be raised to allow flow to pass forward.

This decision was made with the aid of hydraulic calculations and decision flow charts within the contingency plan, allowing for quick and effective decision-making, ensuring flood risk was not impacted upstream and the safety and well-being of the site team working in the channel was never put at risk.

The Canklow Regulator is the furthest downstream of the three Regulators, approximately 3.5km upstream from the confluence of the River Rother and the River Don at Rotherham.

The existing structure consists of a single electrically powered vertical lifting sluice gate operated by an electric wire rope hoist, comprising a drive motor gearbox assembly, cross shaft with integral rope drums, and support bearings.

To improve resilience and the operation and maintenance of the asset, JBA-Bentley is completing the detailed design and build of a new vertical regulator gate and associated MEICA and civils infrastructure.

The MEICA structure consists of a 20.3-ton vertical gate, mounted on a new steel bridge and working platform, which shall also house 13.5 tons of drive equipment for operating the gate.

Two 4kW motors, working in a duty/standby configuration, will provide drive to the gate via bevel and gearboxes, which turn a single driveshaft spanning the width of the gate. On this driveshaft, one at either end of the gate, are rack and pinion gear assemblies, which convert the rotation of the driveshaft to the vertical motion of the gate. The total gear ratio from motor to driveshaft is an approximate reduction of 4410:1, allowing relatively small motors to be specified.

To support the new gate structure over the next 50 years, a new anchor restraint system has been designed. A buried sheet-piled ‘dead-man’ wall will be installed with ten 36mm anchor rods, evenly spaced, connecting to a waling beam on the wet side of the existing channel wall. This will be mirrored on both riverbanks.

The new infrastructure replicates the existing system, which has been determined to be past its design life and insufficient in supporting the new gate.

The existing superstructure of the control houses will be demolished, the foundations will be retained and extended where required to support the new gate structure using cast-in bolt sets.

A new permanent crane pad will be constructed on the south bank for the construction, maintenance, and decommissioning of the gate. This will double as parking spaces for EA operatives when not being used by a crane.

The JBA-Bentley team worked collaborative to optimise the delivery. This meant that site constraints were identified, and the design was completed with buildability and safety as the focus. A key constraint on the scheme is the proximity of the Northern Power sub-station and overhead power lines. The design of the dead-man walls, crane pad, and steelwork platform was completed to ensure that the plant and temporary works required for construction and installation were outside of the powerline exclusion zones.

The Woodhouse Mill Regulator is situated between Canklow and Meadowgate. It uses a single electrically powered vertical lifting gate to retain water. This gate is operated by an electric wire rope hoist, which includes a central drive motor and gearbox assembly, half shafts, spur and pinion driven rope drums, and support bearings, all counterweight assisted.

JBA-Bentley is currently carrying out hydraulic modelling on behalf of the EA as part of the optioneering phase. The options include passive solutions, such as a baffle or orifice plate spanning the width of the channel to continue to utilize the upstream storage. Due to the size of the Don catchment, the modelling required three individual models to be run together:

Multiple return periods are being considered, resulting in hundreds of models runs. The modelling also uses a continuous simulation approach, which adds to the complexity of the model runs.

The upgrading of infrastructure of the Don Regulators will ensure continued flood risk benefits into the future for the Don Catchment and surrounding area with improved resilience and reliability of the new assets. Alongside the reduction in flood risk, the environment and biodiversity will improve in the River Rother as a result of the Meadowgate Fish Pass.

The Living With Water (LWW) Partnership was formed following the 2007 floods when 16,000 properties in Hull and East Riding were flooded. It became clear that no single agency accepted any responsibility outside of their own term of reference, but that each had a part to play in maintaining the waterways in the city of Hull which contributed to the floods. The partnership brings together Yorkshire Water, Hull City Council, East Riding of Yorkshire Council, Environment Agency and University of Hull to enable them to collaboratively deliver flood alleviation schemes in the city. The first of its kind in the UK, the partnership aims to reduce flood risk in high-risk areas, while combining blue-green principles to deliver sustainable, low carbon solutions, encouraging knowledge share between all parties, building community resilience, improving local areas by providing biodiversity net gain.

The principles of the project are to allow exceedance flows from heavy rainfall, for which there is no capacity in the sewer network or nearby watercourses, to flow above ground via existing road accesses between properties, into detention basins retrofitted into existing green spaces in the area. The stormwater can be retained away from properties and returned to the sewer network once there is available capacity and the network is no longer surcharged.

The road access, or ‘10fts’, between properties are lowered to create a channel for stormwater to flow from the highway into the Aqua Green. A headwall and return sewer are installed from the low point of the Aqua Green, connecting into the existing sewer network in the main highway. Flows leave the Aqua Green under gravity, meaning that no mechanical or electrical elements are required for the operation of the solution. The lowering of the 10fts meant that property protection measures were required to the properties adjacent to the 10ft to prevent the solution resulting in them to be at greater risk of flooding. Existing boundary fences were replaced with new fence panels installed on concrete gravel boards to provide a waterproof barrier between the 10ft and the property.

Across the three Aqua Greens, over 1800m3 of storage has been proved. With a traditional grey infrastructure project, providing the same storage would have had a much higher embedded carbon measure, could not have been constructed in the small areas that were available and would have required some form of M&E installation with associated ongoing maintenance and running costs.

The concept design was carried out by Stantec, who produced a full hydraulic model of the whole area to determine where the highest flood levels are seen, to identify the green spaces that would provide the most benefit if they were developed. A total of 11 green spaces in the area were investigated, with cost benefit analysis carried out to establish which of those spaces would provide the most benefit for the community. Three sites were selected to be developed in the first Work Package (WP1) with a further three sites to be developed in Work Package 2 (WP2).

The overall project programme meant that long term groundwater monitoring could not be carried out prior to the design process for WP1. For design calculations, groundwater therefore had to be assumed to be at ground level, which resulted in flotation of the liner and as a result, an additional drainage later needed to be installed below the liner to prevent flotation.

During the construction of WP1, it was observed that the Aqua Greens were retaining water before the liner was installed and that the as clay of very good quality. For WP2, permeability testing and longer-term groundwater monitoring were able to be carried out. This determined that the natural clays were of higher impermeability than the geosynthetic liner and that the groundwater was not as high as was believed during the design phase for WP1. It was therefore discussed and agreed with all relevant parties that the additional geosynthetic liner did not need to be included on site. This saved a total of two weeks on the programme for WP2, approximately 60 tonnes of carbon, material costs of approximately £60,000 and removed the risk of delays associated with the liner install in wet weather.

Construction for WP1 was from October 2023 to December 2024, with works still progressing on the WP2 sites. Sole access to the green spaces via 10ft wide access tracks introduced some difficulties to the construction. Only small plant could be used and the 5m wide liner had to be cut to 2.5m for delivery to the greens. Limited space on site also meant that excavated materials could not be stored at the greens and had to be stockpiled at the site compound, requiring a significant number of dumper loads of materials to be moved on the local road network. The nature of the project and works commencing in winter meant the Aqua Greens frequently flooded during the construction, with water regularly needing to be pumped to the drainage network before further progress could be made.

Due to the location of the Aqua Greens in such close proximity to residential properties, significant community engagement was needed throughout the project, during both design and construction phases, to ensure that the community were kept up to date with what the project would deliver, how the construction works would impact them and ultimately how the SUDs solution would operate and be maintained into the future. Over 30 engagement sessions have been held with the community to date, from the start of the design development to the end of the construction phase. This has been coupled with regular letters and updates on the LWW website, providing the residents with an opportunity to raise any concerns about the works as well as to help to convey the importance of flood alleviation in the area.

To aid conversations with the local community about the Aqua Green developments, computerised visualisations were produced which showed how the Aqua Greens would look upon completion. While the existing greenspaces were mainly neutral grassland before works commenced, the solution was to plant wildflower seeds in the greenspaces upon completion, to increase biodiversity of the area. To provide habitat for wildlife, wildflower areas are maintained less frequently than grassland spaces and this therefore needs to be portrayed to the residents.

The visualisations also helped the MMB team to discuss the proposals with the residents to see if there was anything additional, they would like to see of change as part of the design. Some residents said that they particularly liked the shrubs at the back of one of the green spaces as they provided them some security for their garden, so these were retained as part of the design. Others suggested that the proposed parking areas would not be used and that they did not want to encourage parking on the green spaces, so these were reduced in width to just passing places on the narrow roads.

Continued engagement with the community has been needed throughout the construction phase to answer any queries that the residents had about the works and rectify any problems they had been experiencing. Upon completion of the Aqua Greens, permanent notice boards have been installed at each of the sites to inform the residents of the benefits of the Aqua Green.

The University of Hull have installed testing and monitoring equipment at all three of the Aqua Green sites in WP1 to understand how these Aqua Greens perform. The testing and monitoring equipment included soil moisture probes located above and below the liner; conductivity, temperature, and depth (CTD) probes in the return sewer and a weather station at a local school. The aim is that this data will be analysed and used to improve the design to enhance these assets for future installations. The weather station data is also accessible by the local school so that the data can be used for educating the students about the weather and flood risk of their local area and how we can safely live with water.

The intention is that further testing and monitoring equipment will be included on the WP2 sites so that a comparison can be made between the lined and unlined solutions to see if one of them is more effective at providing the required storage or improving the quality of the water that enters the sewer network.

Since the installation of the first three Aqua Greens was complete, the benefits provided by the Aqua Greens has been visibly clear during periods of heavy rainfall, with quantitative data expected from the testing and monitoring installations within the next few months. These large-scale SuDS basins have provided flood protection to hundreds of properties in an area which otherwise would be at very high risk. Providing the protection via blue-green methods rather than traditional grey infrastructure has resulted in a solution with a much lower carbon impact, while also providing the areas with an improved biodiversity, making it a much more sustainable solution. The blueprint of this project, along with that of the Living With Water partnership, can be applied to other areas across the UK where properties are at high risk to deliver more types of these projects in the future.

Previous business cases had failed to find a viable solution and detailed design work had developed plans for the project to completely renew the existing facility. However, multi-disciplinary teams from the Environment Agency, Arcadis, WSP and Galliford Try Binnies JV (GBJV) worked collaboratively to deliver value engineering achieving savings greater than £12m by re-using existing assets.

The new solution made a switch to fish-friendly electric pumps, avoiding the long-term management of fish and eel screening, and recommended refurbishing rather than replacing the station which would deliver environmental benefits, operational savings and a 90% carbon saving.

The upgrade included:

The project team assisted in the development of the strategic case for investment alongside an update to the Isle of Axholme Flood Risk Management Strategy, and worked closely with the strategy asset management and delivery group ensuring that stakeholder engagement was central to the delivery of the project.

GB JV Ltd, a joint venture between Binnies UK Ltd and Galliford Try, has been the sole engineering design and build provider for the Outline Business Case (OBC), Final Business Case (FBC), and design/construction stages. This ‘cradle to grave’ approach has provided many benefits including the complex construction sequence document (for the whole scheme) created during the FBC which considered severe site constraints and proved an invaluable guide during the design and build phase.

The design involved constructability challenges as the Environment Agency operational team could only allow the release of two pumps at any one time to ensure that the operational plant was never compromised in terms of readiness for flood resilience. It also involved innovative fish pass solutions as site constraints prevented the use of traditional fish ladders and passes.

Binnies’ design team provided a solution which allowed the retention of the existing structure while completely refurbishing the installation. This was achieved by replacing the existing ‘carbon-hungry’ diesel-driven centrifugal flow pumps with electrically driven permanent magnet motors and vertically mounted axial flow pumps within the existing building envelope.

Given the age of the buildings on site, the initial concept design was for the complete demolition of the existing reinforced concrete structure to make space for a new installation. A solutions-focused team looked at plans differently and included extensive early supplier engagement with pump suppliers that crucially unlocked the re-use of the existing structure; a cornerstone of the significant cost and carbon savings. A complete refurbishment rather than the replacement of the existing delivered effective resilience to future climate change.

The existing facility presented a barrier for fish and eel migration and The England and Wales Eels Regulations (2009) required the installation to be upgraded to allow migration of elvers past the facility.

Accordingly, the fish-friendly pumps allow fish to pass downstream safely when pumping and an innovative ‘Elver Mode’ was added into the software controlling the sluicing operation allowing elver access during their migration period and subsequently safe passage into the Three Rivers Catchment and the wider Isle of Axholme, with 224km of main river available to fish and eel passage.

Pentair Fairbanks Nijhuis, the pump supplier, developed a fish-friendly impeller design that ensures fish are not struck on entering the pump, by incorporating vanes to guide them unharmed through the system. The impeller design in conjunction with the variable speed drives ensures optimal efficiency at all times. Low running speeds also improve passage for fish and reduce noise and vibration.

Binnies’ design has also improved operational access to the culverts and flap valves which previously posed significant health and safety risks. Previously, some areas were accessible only by divers and other areas have never been accessed since the TAO was commissioned in 1939 as it was considered too dangerous.

The improved operational safe design has minimised ongoing maintenance difficulties.

Through collaboration with partners and the supply chain the team delivered the OBC and FBC stages to time and budget winning the Best Business Case of the Year at the Environment Agency’s ‘Flood and Coast Excellence Awards’ (2019). GB JV Ltd attained partial sectional completion of the flood defence asset at the end of April 2021 (four pumps operational and available for beneficial use), resulting in the Environment Agency attaining 80% of its stated outcome measures; the reduction in flood risk to 2484 of the total 3105 properties to be delivered by this project.

The remaining 621 properties were realised in November 2021 upon successful integration of the two remaining pumps. This was achieved despite COVID-19 disrupting construction work and storms in 2019 and in 2020 when the Environment Agency needed to operate the diesel pumps to reduce flood risk to the catchment, preventing construction work for approximately three months.

The former pumping station had six large and dangerously loud diesel engines (over 98 dBA when measured outside with the doors closed) and emitted large amounts of exhaust fumes. It was not safe to be inside the building with the pumps operating (even with ear defenders). The building is within 100m of residential properties so pumping activities disturbed the local community.

The new pumps are much quieter with the standby generator designed to be less than 60dBA at 1m. As the pumps can run 24 hours a day for several weeks at a time, the local community have greatly benefited from the removal of noise and air pollution.

The site is immediately adjacent to the Port of Keadby on the tidal River Trent. Close management was required with both PD Ports Ltd and ABP who had equipment within the working area, so the team worked with the port to respond to and work around vessel movements and port operations. A new river fender structure was designed and installed to reduce the risk of damage to the outfall structure from berthing vessels.

In conclusion, the carbon footprint was reduced by 90% throughout the project’s lifecycle using modern efficient fish-friendly electric pumps negating the need for a 3mm eel screen and reduced ongoing lifetime operational expenditure by the use of the existing structure.

When COVID-19 restrictions prevented foreign travel to the pump supplier in Holland, the team implemented remote attendance to witness the programme-critical Factory Acceptance Testing, allowing us to maintain programme. This also enabled a wider team to witness the testing and provided a learning opportunity for team members that would not otherwise have been able to attend. The approach continued with Design Workshops that avoided the need for the Design Team to physically attend site, without compromising the quality of work. The reduced travel also contributed to carbon reduction.

The project has won a number of awards including:

With limited public funding and the increasing need for multifunctional infrastructure enhancements, the scheme offers lessons in the delivery of multiple benefits. The scheme comprises:

Ammanford is located at the confluence of the rivers Loughor, Lash and Marlas. The rivers respond rapidly to rainfall and their channel capacity is limited. Much of the town is built on low-lying land adjacent to the river and overtopping is predicted at multiple locations. If nothing was done to reduce flood risk, 198 homes and 25 business would remain at risk of flooding from the 1 in 100 (1%) annual chance event.

NRW studies demonstrated a strong case for change. The study area was one of the top communities at risk of flooding from main rivers within Western Wales, and facing one of the largest increases in flood risk as a result of climate change. Flooding in the area was predicted to cost the UK some £7.9m in today’s prices over the next century.

With options to slow flows upstream infeasible, optioneering focused on better containment of flood waters in the river corridor. No single flood defence would be able to meet the project objectives, so a combination of raised defences throughout was adopted as the preferred solution.

The scheme was designed to reduce flood risk up to the 1% AEP event, allowing for the impact of climate change over the scheme’s 100-year lifetime; benefiting 349 homes and 37 businesses.

Separately, NRW had identified the case for improvements to Tir-y-Dail weir at the downstream extent of the scheme. The weir was a partial barrier for upstream migration of adult Atlantic salmon and trout, and a complete barrier to adult lamprey and juvenile European eel. Fish passage improvements would unlock 20km of river to migratory fish. The weir was in poor condition but encased a critical main sewer and enabled upstream river level gauging.

The design phase of the scheme involved comprehensive investigations and modelling to understand flood dynamics and identify effective solutions. Key design considerations and innovations are presented below.

Positive solutions to mitigate detriment

At the outset, the team identified a risk of conflict between the initially separate fish passage and flood scheme objectives. A further challenge was mitigating potential flood detriment to other areas. Flood modelling indicated that raising flood defences and making fish passage improvements to the Tir-y-Dail weir would cause unacceptable detriment elsewhere. Typical measures to mitigate the detriment were investigated but were found to be either ineffective or excessively costly (such as additional raised defences upstream) jeopardising the business case justification for the scheme.

The team identified and developed from first principles an innovative solution to locally address issues in proximity to the weir, including an area of ground lowering within the field adjacent to the existing weir and fish passage pre-barrages. This provided additional conveyance around the existing weir and proposed pre-barrages in more extreme flood events, mitigating potential detrimental increases in flood risk associated with both the flood defence and fish passage improvements.

To maximise the benefits of the ground lowering, soils generated from this area were used within the construction of the Tir-y-Dail flood bund, improving the scheme’s earthworks balance and reducing import volumes. The area was also landscaped to provide additional area of riparian habitat.

Balancing earthworks

Two factors made creating an earthworks balance on the project challenging. Firstly, the nature of the scheme and site constraints resulted in limited areas of fill. Secondly, the engineering and chemical parameters of some of the soils excavated were unfavourable.

To minimise the volume of excavated soils that would need to be disposed of off site, the team first addressed the chemical properties of the made ground. Site-specific risk assessments were undertaken to derive appropriate re-use criteria for human health and controlled waters. These were developed into a material re-use strategy, which considered appropriate legislative frameworks and was able to demonstrate that the majority of made ground was chemically suitable for re-use in appropriate scenarios.

To address the imbalance in volumes, the design of the Tir-y-Dail flood bund was reviewed as the primary fill area within the scheme. Flood bunds are most commonly constructed from a homogenous clayey material. This would need to be imported due to a lack of suitable on-site sources. The flood bund was therefore designed to have a ‘cap’ of imported clay to ensure performance against flooding, while the main core was formed from variable site-won material. Slope stability assessment undertaken under various scenarios demonstrated that, as long as the clay cap material was appropriately controlled, the geotechnical parameters for the core material could be significantly reduced.

To allow the contractor flexibility of the site-won materials placed in the core of the bund depending on the sequencing of their works, a project-specific soil material class was created. This was based on a combination of observational and basic material classification controls. This approach resulted in a reduction of 270 wagon loads of soil movements, reducing carbon and impact on local residents.

Sensitive detailing of flood defences

Measures were adopted to ensure the flood defences were sensitively integrated into the local landscape.

Flood walls in publicly viewable areas were finished with brick cladding, form liner finish and imitation stone copings to match local architecture. Coping stones were designed to be structurally integral to the flood wall to minimise their overall height, as well as reduce maintenance and public safety risk. Pillar features were incorporated into the facing of brick cladding at regular spacings to provide visual interest along the expanse of the wall.

Design of the Tir-y-Dail flood bund was tailored to mitigate its impact on the open views from a nearby public right of way. In plan, a curved alignment was specified to conserve an irregular field pattern. In section, slopes were slackened and rounded at the top and bottom to create a naturalistic landform.

A fundamental element of the scheme design was determination of the alignment and form of the flood defences to minimise tree loss along the riparian corridor. An arboriculturist, who was integral to all major design decisions, was embedded within the design team. Every tree was considered individually so that as many trees as possible could be maintained. The resulting designs/design adaptations included micro-siting of flood walls and localised modifications to flood wall foundations in the vicinity of root protection zones.

The project is in the heart of Ammanford, with interventions required in a combination of residential, commercial and public spaces. Multiple rounds of public engagement supported the scheme development, including:

In line with NRWs strategic objectives, enhancements to public space and ecological habitats were fundamental to the scheme design, in addition to reducing flood risk. To provide biodiversity net benefit through increasing connectivity, diversity and ecosystem resilience of the high value riparian corridor, enhancements delivered as part of the scheme included:

Improvements to public spaces in the vicinity of the flood defence works, but also within the wider community, were also delivered as part of the scheme as summarised below:

Environmental impacts were assessed through the Environmental Constraints and Opportunities Record (ECOR), with mitigation and enhancements integrated at an early stage into scheme development, heavily influencing the design process. Potential impacts upon trees, protected species, local community, archaeology, and local landscape, are some of the many that were assessed and mitigated.

The ECOR informed the Environmental Action Plan which formed part of the works information for the scheme and enabled key environmental mitigation measures to be communicated and tracked during the construction phase. The mitigation and protective measures implemented were comprehensive, covering the local community, protected species and environmental quality.

The works were spread across nine locations in Ammanford comprising residential, commercial and public areas. Each location presented unique challenges and constraints. To ensure that the project was executed safely and efficiently, significant effort was made to tailor methods of construction in each location.

The team’s focus on careful planning and attention to detail ultimately resulted in the successful completion of the project.

Early contractor investigation works captured potential clashes with existing utilities and structures. A collaborative working approach from all parties ensured potential issues were rectified before the main construction works commenced.

Working methodology, plant and equipment choices were tailored to the environment at each location to minimise disturbance. Due to the nature of restricted access in some locations, alternative construction methods were implemented. This included the use of a lightweight shuttering system that could be safely manually handled into position.

Collaborative working between the client, contractor and designers allowed early access for in-river works. Note only did this result in the fish passage works being completed with minimal impact on the ecosystem, but also reduced the overall construction programme by many months.

The Ammanford Flood Risk Management and Fish Passage Scheme is a testament to the importance of comprehensive planning, innovative design, and community involvement in flood risk management. By addressing the unique challenges of Ammanford, the scheme significantly reduces the flood risk for hundreds of properties and unlocks 20km of river to passage, as well as providing numerous other environmental enhancements. This case study highlights the critical role of such projects in building resilient communities and enhancing the environment.

The scheme was successfully tested whilst still under construction in September 2023.

The Boston Barrier project was initiated following the severe tidal flooding that occurred in December 2013, which caused extensive damage in Boston, Lincolnshire. This event demonstrated the urgent need for improved flood defences. Boston, situated on the east coast of the United Kingdom, has a history of tidal surges, with significant flooding events also recorded in 1953 and 1978.

In response to the 2013 flooding, the idea for the Boston Barrier was proposed to provide enhanced flood protection. The project received approval in 2017, and construction began shortly after. The barrier is designed to be a state-of-the-art flood defence system, incorporating advanced engineering techniques and advanced technology to offer robust protection against tidal flooding.

The Boston Barrier safeguards ~14,000 properties; including 700 commercial properties. It involved constructing a rising sector gate barrier and associated flood defence walls to protect the town from a 1 in 300-year tidal surge event, even accounting for climate change. The barrier can be raised in just 20 minutes, providing a rapid response to threats from North Sea tidal surges.

This project is a critical component of the UK’s flood risk management efforts and is part of the government’s long-term investment in flood and coastal defences. The initiative aims to reduce flood risk for hundreds of thousands of homes.

Beyond protecting the town from future flooding events, the Boston Barrier project also supports the long-term strategic aspirations of local authorities. It is intended to contribute to economic regeneration in the town and region.

The Boston Barrier Tidal Flood Defence Scheme reduces the risk of tidal surge flooding to properties and businesses in Boston; achieved through the construction of a 28m wide, 11.5m high rising sector flood gate, 7,000 tonnes of sheet piled quay wall, over 2km of flood wall, and a set of 9m wide, 12m high vertical sector gates (VSGs) at the widened entrance to the Port of Boston’s Wet Dock.

The project is designed to reduce the risk of tidal flooding against a 1 in 300-year tidal surge event, equating to an annual exceed probability of 0.33% over its 100-year lifespan.

Mott MacDonald acted as the design partner in a design and build joint venture with contracting partner BAM Nuttall. The Boston Barrier Project operated with the construction partner and client on the same collaborative principles as the aims of the Watercare Design Delivery Partner scope. The scheme also showcases services that align extensively with the key services and core competencies required of the Watercare Design Delivery Partner, including design management services, programme management, technical excellence in all engineering disciplines, geotechnical specifications, physical investigations, interpretive reporting, and analysis prior to full detailed design, consent planning, and environmental management and sustainability expertise.

One of the key engineering challenges of the Boston Barrier Project was designing a system that could operate effectively in the dynamic coastal environment. Engineers had to account for factors such as tidal patterns, storm surge behaviour, and sediment transport to ensure the barrier’s reliability and longevity. Advanced modelling and simulation techniques were used to optimise the design and predict the barrier’s performance under various conditions

In addition to its engineering prowess, the Boston Barrier Project also prioritises environmental sustainability. The location of the barrier was carefully chosen to minimise ecological impact and preserve the natural habitat.

Design efficiencies: The development of the overall basis of design was undertaken with full consideration of climate change. This approach informed the design flood levels and ensured the longevity of the design as a whole. Throughout the design process, various efficiencies were identified and incorporated into the final design to improve outcomes for the client, future users, and the wider environment. Some examples include:

Sustainability considerations: The project leveraged extensive experience in sustainability and sustainable engineering design practices to help the client deliver their first major construction project using the UN Sustainable Development Goals as a framework for monitoring and evaluating the project’s broader successes. The client now uses this project as a benchmark for all future projects, demonstrating how a project team can collaborate effectively to achieve sustainable outcomes as a common goal for all project partners.

Operational forecasting system: The success of the Boston Barrier project relies heavily on reliable coastal forecasting to determine when to trigger the operation of the barrier. Accurate and timely forecasts are essential to ensure the barrier is raised in response to imminent tidal surges, thereby preventing potential flooding.

Without a robust forecasting system, the effectiveness of the barrier could be compromised, leading to inadequate protection for the community and infrastructure. Thus, it is crucial to develop and maintain a reliable forecasting system to guide the operation of such an important flood defence infrastructure.

This proactive approach not only safeguards lives and properties but also lay the foundation for a resilient and thriving community.

To achieve this, the existing tidal forecast model for Boston was refined and improved to provide the most accurate and timely predictions possible of water levels and flood risks from the sea. This system incorporates advanced numerical models, which are calibrated using historical data and real-time observations. These calibrated models have been integrated into the national Flood Forecasting system, aiming to provide a high level of accuracy and reliability. The flow chart below illustrates the key components and process of the operational forecasting system.

Furthermore, the design includes a robust data management framework to handle the input data and output data generated by the forecasting system. This framework ensures that all relevant information is efficiently processed and utilised to make informed decisions about when to activate the barrier. By leveraging advanced technology and comprehensive data analysis, the operational forecasting system plays a pivotal role in the overall effectiveness of the Boston Barrier project.

In summary, the integration of a sophisticated forecasting system is essential for the successful operation of the Boston Barrier. It not only enhances the barrier’s ability to protect the community and infrastructure from tidal surges but also contributes to the long-term resilience and prosperity of the region.

Data collection & analysis: Data collection is a critical component of the operational forecasting system. The project utilises a network of tide gauges and wave buoy stations with recorded water levels, tidal patterns, wave conditions, and associated meteorological conditions. This data is then fed into the multi-regression forecasting models, which analyse the information to predict future water levels in the river Haven, where Boston Barrier is situated, and potential flood events.

Forecasting models: The forecasting models are based on advanced hydrodynamic and statistical techniques. These models simulate the behaviour of tides and surges along the east coast and at Maud Foster Sluice downstream of the Boston Barrier. They take into account various factors such as tide, surge, wind, and local geometry. To ensure their accuracy and reliability, the models were thoroughly tested and verified against 30 years of historical data through both hindcasting and forecasting.

Integration with the operational scheme: The Boston Barrier operational forecasting system is designed to provide accurate predictions of tidal surges and water levels. However, there is no automated response or control system integrated with the barrier’s operations. Instead, the operation of the barrier is manual and based on attendance triggered by forecasted conditions.

When the forecasting models predict a significant tidal surge and the resulting water level in the Haven is expected to exceed the trigger threshold, personnel are alerted to manually activate the barrier to protect the town from flooding. Since the implementation of the forecasting model, the trigger levels for raising the gate have been further refined and adjusted to reduce the number of unnecessary operations at low levels, thereby enhancing the system’s overall effectiveness.

The Boston Barrier Project is not only an impressive feat of engineering but also a showcase of digital innovation. The project leverages advanced digital tools and methodologies to enhance its effectiveness and efficiency.

One of the key digital innovations is the use of Building Information Modelling (BIM) and a Common Data Environment (CDE). These tools enable seamless collaboration among stakeholders, optimise the integration of existing structures, and streamline the design and construction processes.

The use of precast concrete elements and the integration of permanent and temporary works within the twin wall cofferdam exemplifies how the digital tools, such as the project’s CDE and BIM, have contributed to the project’s success. These innovations have resulted in significant time, cost, and carbon savings.

Telemetry-based monitoring & maintenance: The system utilises telemetry feeds to SWANTEL for real-time monitoring and predictive maintenance. Although there is no integration of real-time data from sensors and monitoring systems with the digital model, the telemetry feeds provide valuable insights into the barrier’s performance and condition.  This setup enhances decision-making capabilities and proactive intervention, ensuring navigation safety and the overall effectiveness of the barrier.

Additionally, the project’s hydrodynamic models and BIM model were used to develop flood conditions and virtual navigation simulations for river users even before the scheme was built. This helps identify blind spots and risk areas, ensuring safe navigation through the barrier. By simulating various scenarios, it can highlight potential hazards and provide guidance to mitigate risks, enhancing overall safety for vessels navigating the area around the barrier and the safety of river users.

These benefits demonstrate how the hydrodynamic modelling results not only enhances the operational efficiency and safety of the Boston Barrier but also contributes to the broader goals of flood risk management and community resilience.

Effective communication & community engagement: The work put into the BIM virtual project has ensured that a clear and concise picture is presented to all team members. This approach has unlocked efficiencies, including crucial changes to the design of the control room, hydraulic systems, and future Operation and Maintenance (O&M) ways of working. It has also ensured efficient and effective design to avoid buried obstructions on a well-developed and ever-changing port site.

The BIM model has proven to be a fantastic communication tool, conveying the changes being brought to Boston much better than traditional 2D drawings, especially when communicating with those without engineering knowledge or background. It has been used extensively in both professional presentations and as a key part of the communications package with local interest groups and primary and secondary schools, supporting STEM and community engagement efforts.

The Boston Barrier project incorporates several innovative features and offers numerous benefits that enhance its effectiveness, efficiency, and sustainability. These advancements not only improve the operational performance of the barrier but also contribute to significant cost savings and environmental benefits.

In addition to the previously mentioned advantages, here are the key innovations and benefits of the project in flood forecasting:

These innovations and benefits highlight the Boston Barrier project’s commitment to leveraging advanced technology for enhanced performance, cost-effectiveness, and environmental sustainability. By integrating advanced digital tools and methodologies, the project exemplifies a forward-thinking approach to flood defence infrastructure, ensuring long-term resilience and protection for the community and infrastructure.

The Boston Barrier project showcases innovative flood defence through its advanced operational forecasting system, significantly enhanced the barrier’s effectiveness, efficiency, and sustainability. The project’s success in precise forecasting, cost savings, and carbon reduction highlights importance of advanced digital tools in flood risk management.

Despite the lack of a real-time link between the forecast system and digital monitoring, the project uses telemetry feeds to SWANTEL for real-time monitoring. This setup provides valuable insights into the barrier’s performance, enabling informed decision-making during flood events. This proactive approach not only protects the town of Boston from potential flooding but also fosters economic development and community resilience.

The Boston Barrier’s achievements offer valuable lessons for future flood defence projects. By focusing on accurate data collection, continuous monitoring and improvement, other initiatives can replicate this project’s success, contributing to a safer and more sustainable future.

In summary, the Boston Barrier project exemplifies the power of innovation in flood defence, demonstrating how advanced forecasting and digital technologies can transform community protection against climate change.