Town CLIMATE RISK

Ystradgynlais Flood Risk Data

Ystradgynlais is a town, within the Powys council area. LocalRisk has flood, heat, air and ground-stability data for 401 postcodes in Ystradgynlais; 12 samples are linked at the foot of this page.

0.2% of postcodes in Ystradgynlais fall into Natural Resources Wales's high flood-risk band - below the UK average of about 7%. The band reflects the highest flood risk within each postcode; some properties may face little or no direct flood risk. A further 1.5% sit in the medium band; 98.3% are lower-risk. Across the wider Powys council area the figure is 3.3%, so Ystradgynlais runs lower than its parent council. Two postcodes a few streets apart can land in different bands; what drives the gap is elevation, distance to the nearest watercourse, and how the surrounding drainage performs in heavy rain. The postcode list at the foot of this page links to the full address-level reading for each postcode in Ystradgynlais.

Met Office UKCP18 projections (50th percentile) estimate around 12 days above 25°C per year across the Powys area, averaged over the 2021-2040 period under the RCP8.5 high emissions scenario. These are probabilistic projections - the 50th percentile is the central estimate within RCP8.5; the full range of modelled outcomes is wide and lower emissions scenarios would produce lower figures. Heat exposure within Ystradgynlais varies by property orientation and construction, but the overall heat stress level is relatively low. The headline 12-day figure is a council-level UKCP18 estimate (LAD resolution), not a property-level reading.

Annual mean PM2.5 across the Powys area is 4.5 µg/m³ - close to the World Health Organisation guideline of 5 µg/m³. Within Ystradgynlais, readings are not flat: postcodes within 200 metres of an A-road or major junction routinely run 30-50% higher during weekday rush hours than residential streets two roads back. The figure is a council-level Defra UK-AIR estimate (1km modelled grid).

Ground stability in Ystradgynlais follows the underlying geology more than the postal boundary. The British Geological Survey GeoSure dataset maps clay shrink-swell risk on a 50-metre cell, and properties on the same street can sit in different bands where a clay seam ends mid-road. Pre-1980 housing on clay-rich ground is the most exposed; properties on bedrock or well-drained sandy soils are typically lower-risk. A postcode-level check picks up that variation.

A free postcode check on LocalRisk covers up to six hazards for any address in Ystradgynlais: NRW flood mapping, BGS ground stability, Met Office heat projections, Defra PM2.5, plus coastal erosion and green-space access where relevant. The postcode list below opens an address-level report for each postcode in Ystradgynlais; the council link at the top of this page returns to the wider Powys picture.