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River Cole realignment clears way for Delta Junction viaducts

By Richard High, 04 September, 2025
Aerial view of the re-aligned River Cole near Coleshill, showing the new meandering channel created to enable construction of HS2 viaducts at Delta Junction. The River Cole realignment at Coleshill, Warwickshire, completed ahead of construction of two major HS2 viaducts at Delta Junction.

HS2 has completed a 749-metre realignment of the River Cole in Warwickshire, clearing the way for two major concrete viaducts and associated embankments at the Birmingham Spur of the Delta Junction.

The permanent diversion – the largest river realignment undertaken on the HS2 project – was necessary to create space for the new railway structures. Designed by Mott MacDonald SYSTRA Design Joint Venture and delivered by Balfour Beatty VINCI, the works involved excavating a new channel and re-establishing flow in 2024 before viaduct construction could begin.

The two River Cole viaducts, now under construction, will use reinforced concrete foundations, piers and deck slabs to carry the high-speed line across the re-meandered watercourse. Precast and in-situ concrete techniques are being combined to ensure durability and minimise programme risks.

Computer-generated image of two HS2 viaducts crossing the re-aligned River Cole, with landscaped embankments and green spaces visible on either side. CGI of the two River Cole viaducts at Delta Junction, which will carry HS2 over the newly realigned river channel. Image: HS2

Simon Casey, HS2 Ltd’s head of environment for main works civils, said the project showed how civil engineering can integrate environmental resilience with infrastructure delivery: “The holistic approach to this River Cole realignment is a shining example of climate-resilient infrastructure, environmental preservation and community benefit. It is part of our wider Green Corridor programme and provides a valuable learning legacy for the profession.”

The design team reused natural river gravels from the floodplain to form the new riverbed, cutting carbon in construction and supporting aquatic habitats. Temporary dams were removed once excavation was complete, and monitoring is continuing to assess river flow, sediment behaviour and habitat establishment.

With the river works finished, Balfour Beatty VINCI is progressing the viaduct substructures and embankments. The two River Cole viaducts are scheduled for completion later this year, forming a key part of the complex Delta Junction where HS2 routes diverge towards Birmingham and the north.

HS2 has completed a major river enhancement in Warwickshire, which is the most significant realignment of a natural river on the project.

Concrete at Delta Junction – Key Facts

  • Precast viaduct segments: Six of the Delta Junction’s 13 viaducts use precast concrete segments manufactured at HS2’s Kingsbury facility, weighing up to 80 t each.
  • River Cole viaducts: Reinforced concrete foundations, piers and in-situ deck slabs are being constructed after the river realignment.
  • Foundations: Deep concrete piles transfer loads through alluvial ground to stable strata, providing long-term resilience.
  • Sustainability: River gravels from the floodplain have been reused in the riverbed; cement replacement materials such as GGBS are specified to cut embodied carbon.
  • Design life: All Delta Junction concrete structures are designed for a 120-year lifespan, reducing whole-life carbon and maintenance needs.
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