Land Off Sandford Lane
The Brief
RIDA was instructed to provide a detailed flood risk assessment and drainage strategy for a proposed development located at Land Off Sandford Lane, Kennington, Oxford. The project involves the construction of a new building dedicated to the water-based sport of rowing.
Why the Client Chose RIDA
The client required specialist engineering support to navigate the strict planning requirements associated with building directly adjacent to the River Thames. RIDA was selected for our expertise in delivering bespoke flood mitigation strategies and our proven ability to design compliant, practical solutions for water-compatible developments.
The Challenge
Situated approximately 15 metres from the River Thames, the site is located entirely within Flood Zone 3b, presenting a very high probability of fluvial flooding. In addition to the fluvial threat, the site also faces a high risk of groundwater flooding. The primary challenge was to design a facility that could operate safely and protect its structural integrity during a flood event, without increasing flood risk elsewhere or impeding the natural flow and storage of the floodplain.
The RIDA Difference
RIDA conducted a thorough assessment to design a robust flood mitigation strategy tailored to the site’s specific riverside constraints. To address the significant fluvial flood risk, we proposed an architectural approach that elevates the boathouse on columns, allowing floodwater to freely enter and leave the underside of the building. This innovative design removes only a minor volume from the flood zone, successfully eliminating the need for complex off-site flood compensation.
We established a safe finished floor level (54.738 mAOD) set significantly above the 1 in 100-year storm event plus a 35% allowance for climate change. For the foundational elements and columns in contact with water, a ‘water exclusion strategy’ using resilient, low-permeability materials and reinforced concrete was recommended.
Furthermore, to manage surface water, we outlined a sustainable drainage system (SuDS) hierarchy to ensure no increase in runoff rates. RIDA also incorporated a strict Flood Emergency and Evacuation Plan, explicitly prohibiting rowing activities and site access when the nearby Sandford-on-Thames Lock exceeds ‘Typically High’ gauge levels to ensure absolute user safety.
The Outcome
The comprehensive assessment demonstrated that the proposed boathouse fully complies with National Planning Policy Framework (NPPF) guidelines for water-compatible development. By integrating an elevated design and a clear emergency evacuation protocol, the strategy successfully proved that the site can be safely developed and managed over its lifetime without adversely impacting off-site flood risk or public safety.
