Flood Risk Assessment — Office-to-Residential Conversion, Bordesley Green, Birmingham
We prepared a Flood Risk Assessment for an office-to-residential conversion at 155-157 Muntz Street, Birmingham — a Flood Zone 1 site with low flood risk across all sources, where the focus was on delivering a compliant SuDS strategy to ensure no increase in surface water runoff.
Flood Risk Assessment — Office-to-Residential Prior Approval in Flood Zone 1, Bordesley Green, Birmingham
Location: 155-157 Muntz Street, Bordesley Green, Birmingham, B10 9SJ, Birmingham City Council | Client: Arkidraft Ltd | Services: Flood Risk Assessment
Prior Approval with a Clean Risk Profile
Office-to-residential conversions under prior approval still require a technically complete flood risk case, even where every indicator points to low risk. At 155-157 Muntz Street in Bordesley Green, the Flood Zone 1 classification and low risk across all modelled sources made for a straightforward assessment — but one that needed to demonstrate full NPPF compliance and address surface water management to satisfy Birmingham City Council.
We were appointed by Arkidraft Ltd to prepare the FRA for a proposed conversion of the existing office building at 155-157 Muntz Street into residential accommodation.
Site Context
The site is located within a predominantly urban area of Bordesley Green in the Birmingham City Council area. The existing building footprint is retained, meaning no change in impermeable area and no reduction in floodplain storage.
Flood Risk Assessment — All Sources
Every flood source was assessed and confirmed as low risk. Fluvial risk was low — Flood Zone 1, with an annual probability of river flooding of less than 0.1%. Tidal risk was negligible. Surface water (pluvial) risk was low, with EA mapping confirming the site lies outside identified areas of elevated surface water flood risk. Groundwater risk was low. Sewer flooding risk was low. Artificial source risk was low.
No historic flood events were recorded at the site.
Surface Water Management
Through the implementation of suitable surface water management techniques, the development was confirmed not to increase flood risk to the surrounding area. The existing building footprint is maintained, so the impermeable area remains unchanged. Standard resilience measures were specified for the ground floor construction to address the change in vulnerability classification from commercial to residential use.
Outcome
The FRA provided Birmingham City Council with the technical evidence to support the prior approval application, confirming full NPPF compliance. The assessment demonstrated that the conversion can proceed safely without increasing flood risk — a clean result, but one that required proper documentation given the change to a more vulnerable land use classification.