4 minute read
River Cole realignment
Bird's-eye view looking southwest over the realigned River Cole during summer, ten years postconstruction. © HS2 Ltd
Despite the cancelling of HS2 from Birmingham to Manchester, the line from London represents a major investment in landscape-led design.
In Phase One of HS2
Britain’s new zero-carbon high-speed railway – the Delta Junction in the West Midlands – will be one of the project’s most complex network of structures. It is a triangular section made up of nine precast segmental viaducts, embankments, and other bridging structures, with around 10km of track crossing a network of motorways, roads, and rivers. At the very southern tip of the Delta Junction is the River Cole, which needs to be realigned in order to build two of the viaducts.
The design challenge offered a great opportunity not only to conserve and restore, but also to enhance the landscape by creating new wildlife areas inspired by local heritage around the proposed viaducts. Meanwhile, new footpaths and cycleways will promote active travel and enable people to explore the rich history of the area. Wetlands, ponds, and habitats will also provide homes for fish, amphibians, dragonflies, otters, great crested newts, reptiles, and badgers, increasing the local biodiversity.
The land beside the River Cole has been identified as a heritage hotspot, with a rich history from pre-Roman times up to the middle of the last century. The main heritage assets of the area, the Elizabethan Manor of Coleshill Hall, and Coleshill Manor parkland with the Elizabethan Garden, itself uncovered by HS2 archaeologists, have been used by the landscape architects involved to influence the design in this location.
For the area closest to the viaducts, a parkland landscape has been designed that flows down to the realigned river. Further south, a grid of tree planting has been included, which harks back to a similar feature found in the Elizabethan era. The landscape-led approach that is applied to this and other projects along the HS2 route includes a variety of nature-based solutions that are developed by an interdisciplinary team of experts. Landscape architects have worked closely with the river engineers to ensure compliance with hydraulic constraints. The river realignment is designed to simulate the existing flow capacity, maintaining an adequate radius to avoid erosion at meanders and to ensure the diversion does not exacerbate risk for the 120-year lifetime of the project.
The landscape design ensures a naturalistic watercourse, providing habitat for the existing valuable ecological assets such as fish and aquatic invertebrates. The incorporation of replacement floodplain storage areas offers opportunities for additional planting, and ecological habitats that further contribute to the project’s biodiversity. It is with much anticipation, through the eventual monitoring, that we will discover which species will establish and thrive in this new water course habitat.
With habitat connectivity as a key objective, the riverbanks have been arranged into distinct planting areas linked to local flora, with swathes of wet grassland and riparian planting that provide ecological habitats, alongside a small ecological park adjacent to the River Cole viaducts.
The incorporation of replacement floodplain storage areas offers opportunities for additional planting, and ecological habitats that further contribute to the project’s biodiversity.
The introduction of the HS2 infrastructure and its associated developments have provided a unique opportunity to establish a new relationship between the railway, the landscape and the local communities by enhancing the historical significance of the area and its ecological features.
Consequently, the landscape integrates the railway into its surrounding environment by delivering various social and environmental benefits, whilst celebrating its local richness.
Christoph Brintrup is Head of Landscape for HS2 Ltd.
