The National Museum of Wales has several storage facilities where it keeps its various collections when they are not in the museum. At one site in Nantgarw near Cardiff, there is spare land which the Museum wished to utilise by building two office blocks which could be rented sold on.
Richard Allitt Associates were commissioned to undertake a Flood Consequence Assessment. The site was located partially within Zone C1 as defined by the development advice map referred to under TAN15 Development and Flood Risk (July 2004) which meant that there was a risk of fluvial flooding from 1 in 1,000 year events for part of the site.
A GPS survey was undertaken by RAA for the area and the existing ground levels of the proposed site ranged between 40.7m AOD and 40.3m AOD.
The probability of the site flooding is less than 0.1% (1 in 1,000 years) as the EA predicts flood levels of 39.36mAOD for a 1 in 1,000 year return period event and the finished floor level of the proposed buildings will be no lower than 40.5m AOD. The proposed car park area alongside the existing warehouse at about 39.5mAOD is also above the 1 in 1,000 year flood level.