LOCATION:
The North Portsea Phase 5 flood protection project is the final stage of a comprehensive five-phase scheme designed to safeguard Portsmouth’s coastline. Managed by Coastal Partners for Portsmouth City Council, this £8.2 million contract aims to protect 4,200 homes and 500 businesses from flooding along Ports Creek.
Key elements of the project:
Our work comprises a 1.3km long sloping rock revetment with a raised earth embankment, forming a robust barrier against coastal flooding. The works include:
- Construction of rock revetment and flood embankment along the full site length.
- Installation of gabion baskets, Flex MSE retaining walls and sheet piles.
- Creation of two compounds for offices, welfare, car parking and material storage.
- Diverting public footbridges to maintain safe access.
- Use of advanced technology such as GPS-controlled excavators and rollers, drone surveys and a 360° camera site tour for progress monitoring and quality assurance.
Challenges
The project faced several significant challenges:
- Limited space and access: The site was constrained by the creek to the north and moats to the south, making logistics and material delivery complex.
- Public interface: Ensuring the safety of the public and workforce was paramount, given the proximity to residential areas and busy transport routes.
- Existing services and Network Rail: Navigating around existing utilities and railway infrastructure required careful planning and coordination.
- Testing and supply: Over 30 possible supply sources were investigated, and a rigorous on-site material testing regime was implemented.
Solutions
Knights Brown has overcome these challenges through innovative approaches:
- Scaffold bridges: Temporary scaffold footbridges were installed to divert pedestrians, eliminating public interface with construction plant and lorries.
- Efficient logistics: A thorough traffic management plan was developed, including designated pedestrian walkways, lorry driver briefing cards and one-way site access to minimise risks.
- Technology adoption: GPS machine control reduced the need for workers in active zones, improved quality control and optimised material usage. Drone surveys and live compaction data enhanced monitoring and reporting.
- Stakeholder engagement: The project team host site visits for local schools, universities and work experience students, resulting in apprenticeships and positive community impact.
Outcome
The North Portsea Phase 5 project is delivering substantial benefits:
- Enhanced flood protection for thousands of homes and businesses.
- Improved safety for workers and the public through advanced site management and technology.
- Social value through education, apprenticeships and community engagement.
- Cost savings and efficient delivery, with Knights Brown’s approach proving notably cheaper than alternatives and enabling completion within a single earthworks season.
