The Bothy
The Brief
RIDA Reports Ltd was appointed to undertake a detailed flood risk assessment for a proposed residential development at The Bothy in Milton-under-Wychwood. The project involves constructing an extension to the existing building and repurposing it to serve as residential accommodation. Given the site’s proximity to a nearby watercourse and varying flood zone classifications, an in-depth analysis was required to determine the viability of the project.
Why the Client Chose RIDA
The client required specialised expertise to navigate complex national and local planning policies regarding flood risk. RIDA was chosen for its proven ability to deliver detailed flood risk assessments that accurately identify site constraints and provide practical, compliant mitigation strategies tailored specifically to residential property extensions.
The Challenge
The primary challenge involved navigating the site’s specific flood zone classifications; while the main building and proposed extension sit within Flood Zone 1, the designated parking area falls within Flood Zone 2. Although the risk from surface water flooding was deemed very low, the site’s free-draining soil presented a potential groundwater flood risk. Furthermore, as the residential accommodation is classified as a ‘More vulnerable’ development, the project required strict adherence to the National Planning Policy Framework (NPPF) sequential risk-based approach to ensure the works would not impede water flows or increase flood risk elsewhere.
The RIDA Difference
RIDA conducted a detailed flood risk assessment to evaluate fluvial, surface water, and groundwater risks against current NPPF guidelines. To address the specific challenges of the site, RIDA established a comprehensive mitigation strategy directly linked to the identified risks. To protect against potential surface water entry, RIDA recommended raising the internal final floor level of the existing Bothy by 150mm. To effectively mitigate the groundwater risks, the strategy incorporated a geomembrane under the floor slabs and a waterproofing membrane on the wall bordering the higher-risk flood zone. Additionally, RIDA advised that all external levels remain unchanged to eliminate the need for flood compensation, and specified a permeable parking area to provide essential flood water storage within its sub-base.
The Outcome
The detailed flood risk assessment successfully demonstrated that the proposed development fully complies with the NPPF. By integrating strategic resilience measures and sustainable drainage features such as the permeable parking area, RIDA proved that the extension would not result in a net loss of floodplain storage or negatively impact the surrounding area, thereby robustly supporting the proposed planning application.