Planning permission was sought for a residential development at a site approximately 1.6 km southwest of the centre of Newtown in Powys. The site comprises 2 areas; one to the north of the A489 and one to the south, and at the time of the Application was being used to graze livestock. The flood vulnerability class of the area, as defined in the TAN15, was ‘less vulnerable’. The proposed site’s use for residential development has the classification of ‘highly vulnerable’.
The Mochdre Brook forms the eastern boundary of both areas of the site, which is an incised stream that flows northwards to its confluence with the River Severn some 165 m north of the site.
The site is mostly classified as Zone A as defined in Technical Advice Note 15 (TAN 15) and shown on Welsh Government’s Development Advice Map (DAM), where the probability of fluvial flooding in any one year is less than 1 in 1,000 (Annual Exceedance Probability, AEP <0.1%). A smaller area of the site along the eastern edge (adjacent to the Mochdre Brook) is designated as Flood Zone C2. This is an area where the probability of fluvial flooding in any one year is 1:100 (AEP 1%). Given that the site area exceeds 1 hectare a Flood Consequences Assessment (FCA) was required in accordance with TAN15 guidelines.