An aerial map of trees is helping Cardiff Council reduce the risk of surface water flooding.

The National Tree Map, created by Bluesky International, provides accurate height, location and canopy coverage data for more than 400 million trees across the UK. Intelligence from the maps, combined with data detailing the location of Cardiff's highways drainage gullies enables cleansing and street sweeping programmes, along with community engagement, to be prioritised for areas most at risk of falling leaves blocking drains.

Cabinet Member for Climate Change, Cllr Caro Wild, said: "As Cardiff experiences increasingly extreme weather as a result of climate change, surface water flooding poses a growing risk, and this is a simple but highly effective way of using location-based intelligence to achieve operational benefits."

The Council currently has responsibility for around 100,000 highway gullies, or drains (pits covered by an open metal grating typically located at the edge of the highway), which are designed to drain rainwater, and other surface run off, into a drainage system where it can be conveyed to an appropriate discharge point.

As part of the national dataset, the Bluesky National Tree Map has captured data of trees 3 metres and taller in the Cardiff area. Using the open-source Geographical Information System QGIS, to compare the proximity of trees and gullies, close to 5,000 or five percent of gullies were deemed to be at risk of leaf fall.

Other applications of the Bluesky data used by teams at Cardiff Council include planning, drainage and arboriculture. For example, the data helps with approval of the Sustainable Drainage Systems (SuDS), mandatory in Wales for developments of 100 metres square or more and allows assessment of the impact of trees on other types of watercourses to help prevent flooding. The National Tree Map data also helps arboriculturists plan maintenance work for protected trees and inform planting strategies for parks and urban forestry.

Ralph Coleman, Sales Director at Bluesky, added, "The feedback we get regularly from users of the National Tree Map is that it enables analytical work to be carried out on the desktop whereas previously site visits might have been needed, this saves time and valuable resources. The National Tree Map delivers accurate insights rapidly, shortening lead times for valuable projects that contribute to the safety and security of the public. The data is used by a wide range of businesses and organisations from local authorities and academia to architects and planners, renewable energy companies and environmental organisations."

Created using innovative algorithms and image processing techniques, using the most up-to-date aerial photography and terrain data for the whole of Great Britain and Ireland, the National Tree Map, was launched over 11 years ago, initially for use in the insurance sector.