The removal of the existing tidal barrage at Ormesby Beck presented a number of challenges, requiring close collaboration across our modelling, engineering and environmental teams, as well as the wider project delivery team. To determine the impact of removing the barrage on flood risk and the potential to create intertidal habitat we were tasked with conducting a technical appraisal of how best to remove the barrage and navigation screen.

To fully assess the impact of any planned work, our team conducted topographic surveys, created a detailed 3D model of the existing barrage and also conducted a biodiversity baseline study. Adopting this multifaceted approach meant we were then able to generate and appraise several different options, before recommending a preferred option and completing an outline design for the work.

As well as forming a key part of the appraisal process, sharing the JBA-developed 3D model of the barrage with the project delivery partners meant it could be used to plan a detailed cutting sequence, which would allow for the barrage to be safely removed in instalments. The model also played an important role in helping to develop the temporary works – something which was integral to the design and overall success of the project.

A key technical challenge was also ensuring the temporary works allowed for both fluvial and intertidal flooding, whilst adhering to strict ecological constraints due to the presence of European eels. This required technical excellence and innovation at both the design and delivery phases. The solution to maintain fish and eel passage, as well as the flows, was to open the existing flap valves on the structure ahead of installing a cofferdam and removing the existing structure in two separate phases.