AECOM was commissioned by Coastal Partners - on behalf of Havant Borough Council - to deliver an Outline Business Case for a Flood and Coastal Erosion Risk Management (FCERM) scheme at Langstone.
Protecting a community
The project involved developing and appraising options to manage the flood and erosion risk in accordance with the FCERM appraisal guidance. A preferred option was recommended and adopted by the client in order for an outline design to be delivered.
The 1 km Langstone frontage features number of constraints which were considered in the option appraisal process. There are a number of properties in very close proximity to the water’s edge which limit space availability, along with a large number of buried services and utilities along the frontage and a variety of environmental and heritage designations in the area such as SAC, SPA and SSSI.
In addition to the flood and erosion risk to the Langstone frontage, the A3023 main road passes through the site. This road is the only access road to and from Hayling Island. The Langstone scheme was therefore viewed as an essential element when considering the need to protect access to Hayling Island during extreme flood events.
AECOM services included simulation of the Environment Agency’s East Solent hydrodynamic model to determine the number of properties and other assets at risk from flooding and erosion over the next 100 years. This was supported by a visual defence condition assessment undertaken by the project team to determine the estimated residual life of the existing defences.
Based on the baseline evidence gathered, the project team then undertook an economic assessment to establish the economic damages and benefits of potential options over the next 100 years. If nothing was done to manage the flood and erosion risk, the economic damages were estimated to be £13million.
In addition to the economic assessment, the project team also undertook a Gross Value Added (GVA) assessment which valued the dynamic impact to the local economy of flooding at the site. An environmental appraisal and stakeholder engagement of options was also carried out to support this process. The AECOM team supported the delivery stakeholder workshops, public exhibitions and individual meetings, providing non-technical summaries to residents in order to – ultimately – arrive at an agreed option to develop.
“Pro-active attitude to problem solving. Delivering work packages on time and on budget to an extremely high quality. There looks to be a great willingness within AECOM to deliver better than expected results to the client.”
Coastal Partners feedback on AECOM’s delivery on the Langstone Scheme.
Innovative solutions
Owing to the constraints at the site, the project team considered a variety of alternative flood defences, such as flip-up barriers and glass panelled walls as part of the leading option. The recommended leading option was ratified by the project board and the project team are currently working on developing the detailed design for the scheme.