TYN Y RHOS, Gwyddelwern, Corwen, Denbighshire, LL21 9DE Data via plota.co.uk

The Environment Agency flood map for planning. Homes in zone 3 must also pass the sequential test. Surface water flooding is a separate map.

Natural England advice: extra wastewater in these catchments harms protected habitats, so schemes must offset their nutrient load, usually through credits.

Where development of farmland is needed, policy prefers poorer land over the best and most versatile (grades 1, 2 and 3a). Three sources: Natural England's post-1988 field surveys, which are definitive where they exist; the Defra predictive map for England (2025) and the Welsh Government predictive map, modelled from the soil map with 3a and 3b split; and the 1970s provisional map, which planners and other services still show, coarser and with grade 3 undivided. Where the provisional and predicted grades disagree, treat the predicted grade as the current estimate and expect an application to carry its own survey.

From the British Geological Survey and UK Health Security Agency indicative atlas. Under building regulations, as the BRE guide BR 211 (2023) sets out, new buildings and extensions need basic radon protection from class 3 in England and Wales and from class 2 in Scotland, and full protection from class 5. The class at the site itself, from the detailed BGS map, decides which.