Protecting riverbanks whilst promoting biodiversity
location
Norfolk
The Challenge
The project required delivering long-term erosion protection within a highly sensitive and ecologically designated area. Stability issues along sections of the sheet-piled bank, combined with low flood protection levels, created a risk of further deterioration and potential habitat loss.
The challenge was to reinforce and stabilise the riverbanks while minimising disruption to the surrounding environment and supporting the recovery of native vegetation within the protected SSSI area.
The Solution
HEP completed the works in two phases, in 1995 and 1999, using asphalt-based materials to provide durable and environmentally compatible erosion protection.
In the first phase, the raised embankment was protected with 150mm of Open Stone Asphalt (OSA) placed on a geotextile membrane to prevent erosion and enhance slope stability. During the second phase, existing concrete slabs in front of the sheet piles were removed, and the uneven profile regulated using a minimum 100mm of Lean Sand Asphalt (LSA), followed by 125mm of OSA to provide a robust, flexible surface.
A soil-filled trench was created along the crest to encourage vegetation growth, helping the bank blend naturally with its surroundings and promoting biodiversity.
How We Delivered
Both phases were completed over two-month periods, with works planned to align with environmental restrictions and water-level management requirements. Material deliveries and placement were carefully managed to avoid contamination, minimise disturbance, and maintain safe river navigation throughout construction.
The use of LSA and OSA provided a seamless and low-impact approach, offering long-term protection with minimal maintenance while supporting the ecological value of the river corridor.
Community & Environment
Located within a SSSI and the Norfolk Broads National Park, the River Yare works demanded a strong environmental focus. All materials and working methods were selected to minimise ecological disturbance and preserve the character of the landscape.
The addition of soil and vegetation at the crest helped restore natural habitats, supporting biodiversity along the river margins and improving aesthetic integration with the surrounding environment. The project delivered tangible environmental benefits while maintaining essential flood protection for local communities.
The Outcome
The completed works at the River Yare provided lasting riverbank stability and improved flood defence without compromising the area’s ecological value.
The combination of Lean Sand Asphalt (LSA) and Open Stone Asphalt (OSA) delivered a resilient, low-maintenance solution that continues to perform effectively decades after completion. The project stands as an early example of environmentally sensitive engineering — balancing protection, performance, and biodiversity enhancement within one of the UK’s most important wetland environments.
