Flood Risk Assessment — Flood Zone 3 Temporary Restaurant Dome, Bingham Riverhouse Hotel, Richmond upon Thames

Flood Risk Assessment — Temporary Restaurant Dome in Flood Zone 3, Bingham Riverhouse Hotel, Richmond upon ThamesLocation: 61-63 Petersham Road, Richmond upon Thames, TW10 6UT, London Borough of Richmond upon Thames | Client: Bingham Hotel & Restaurant Limited | Services: Flood Risk Assessment & SuDS StrategyA Flood Zone 3 Site on the Tidal ThamesNot every project in a high-risk flood zone involves major structural intervention. Sometimes the challenge is demonstrating that a relatively modest proposal — in this case, a temporary glazed dome for restaurant use — sits within Flood Zone 3 on the tidal Thames, and making a technically robust case that it can proceed without increasing flood risk to the site or the wider catchment.We were appointed by Bingham Hotel & Restaurant Limited to prepare the FRA for a proposed temporary dome structure within the grounds of the Bingham Riverhouse Hotel at 61-63 Petersham Road. The site is partially located in Flood Zone 3, directly adjacent to the River Thames, with the western boundary facing the river. It sits between residential dwellings to the north, Petersham Road to the east, and a public park to the south — well embedded in the urban fabric of Richmond, but very much within the tidal Thames floodplain.Understanding the Flood Risk ContextThe assessment evaluated all relevant flood sources. Fluvial and tidal risk from the Thames was classified as high, consistent with the Flood Zone 3 designation confirmed by the Environment Agency's Flood Map for Planning. The low-lying western portion of the site faces the river and is subject to tidal influence. EA flood defence mapping confirmed that the site does benefit from formal flood defences providing protection up to the 1-in-100-year annual probability event, though the site partially falls within the 1-in-100-year plus climate change design flood extent.Reservoir breach risk was classified as high. EA reservoir flood mapping confirmed the site partially falls within the wet-day breach flood extent — the more severe scenario that models inundation when a reservoir fails during an already elevated river flood event. This is a precautionary consideration rather than an active operational risk, but one that the assessment addressed directly.Groundwater risk was assessed as medium. The underlying geology is London Clay Formation, a low-permeability bedrock that limits the potential for groundwater emergence at the surface. BGS mapping recorded no superficial deposits, and nearby borehole data (reference TQ17SE48, approximately 40 metres north) indicated made ground, ballast, and clay. The Richmond SFRA (2021) places the site within the 50–75% groundwater susceptibility band, but outside the permeable superficial deposit zone that would significantly elevate groundwater risk. No historical groundwater flooding incidents were identified.Surface water and sewer flooding risk were both assessed as low. EA surface water mapping confirmed the dome location sits outside the modelled extents of elevated pluvial risk, with the masonry boundary walls and established road drainage infrastructure intercepting surface flows from the adjacent Petersham Road. Thames Water records in the Richmond SFRA identified one indoor and one outdoor sewer flooding incident in the wider area — insufficient to elevate the risk classification for this site.Why the Dome Presented No Floodplain Storage IssueThe critical technical question for any development in Flood Zone 3 is whether it reduces available floodplain storage or alters modelled flood behaviour. For a structure of this nature, the answer was straightforwardly demonstrable. The temporary dome is a lightweight glazed structure with a negligible volumetric footprint. It does not displace floodwater, does not obstruct flow paths, and has no mechanism by which it could alter the modelled flood extents or water levels on the site or in the wider catchment.The dome is used exclusively for restaurant dining and is not occupied outside operational hours. This means that in the event of a flood warning, the structure would already be unoccupied, and safe evacuation of diners during operational hours is achievable given advance warning from the Environment Agency's Floodline service.Sequential and Exception Test ExemptionThe proposed development constitutes a minor householder application and is therefore exempt from the Sequential and Exception Tests under footnote 62 of the NPPF. This was clearly established in the assessment, removing a layer of procedural complexity that might otherwise have applied.OutcomeThe FRA demonstrated full compliance with NPPF flood risk policy, providing the London Borough of Richmond upon Thames with the technical evidence needed to support the planning application. The assessment confirmed that a temporary restaurant dome within a Flood Zone 3 hotel grounds can proceed safely, provided its lightweight construction and operational characteristics are properly characterised and documented.