Overview
Although the Dew Drop Inn site in Peacehaven was located in Flood Zone 1, and therefore at low risk of flooding from rivers and the sea, the EA’s pluvial dataset showed that the site was at high risk of surface water flooding, with potential flooding during a 1 in 30 year event.
This created a significant constraint on how the site could be safely redeveloped without increasing flood risk either on-site or to neighbouring areas.
Aegaea’s Approach
To address these challenges, Aegaea carried out a detailed Flood Risk Assessment supported by bespoke direct rainfall hydraulic modelling. This modelling allowed different building locations and footprint designs to be tested, assessing how each option might affect surface water flow paths, flood displacement, and the need for flood compensation.
Through this iterative process, it became clear that the safest approach was to retain a building footprint similar to the existing structure, while adjusting access arrangements and internal layouts. This ensured that commercial units, classified as less vulnerable, were positioned on the ground floor, with residential units located on the upper floors where the risk was lower.
Alongside the Flood Risk Assessment – Aegaea provided a comprehensive surface water and foul drainage strategy for the site. A range of Sustainable Drainage Systems (SuDS) were considered; however, due to the chalk geology of the site, infiltration was not deemed feasible. Guidance in CIRIA Report C574 and BRE365 requires that infiltration features such as soakaways are situated at least 10m from any existing or proposed structure, which ruled out this option early in the design process.
Instead, after reviewing the SuDS hierarchy set out in CIRIA C753, Aegaea engaged with both the Lead Local Flood Authority and Southern Water to agree on a suitable drainage approach. This included connecting to the existing surface water network, while delivering betterment through on-site attenuation, appropriate water treatment provisions, and restricting runoff rates to ensure surface water was released into the system in a controlled, policy-compliant manner.
The Outcome
The final design delivered a safe, resilient, and policy-compliant redevelopment that successfully managed the site’s high risk of surface water flooding The combination of detailed modelling, careful layout planning, and early engagement with key authorities ensured that the development avoided increasing flood risk elsewhere, achieved a workable drainage solution despite site constraints, and incorporated SuDS in line with best practice. The project illustrates how a robust problem–solution approach can unlock challenging sites and support sustainable redevelopment.
