The British Geological Survey took to the air on 20 November 2009 in the aftermath of the flooding, which devastated homes and businesses in the North West England and South West Scotland, to find out how modern flooding compares to ancient flood areas. BGS photographer Fergus MacTaggart observed flooding from 600m (2000 ft) as he flew over the worst affected areas around Lockerbie and Dumfries.

Why do geological maps reflect areas prone to flooding?

Areas which have been flooded in the past have deposits of clay, silt and sand left by the flood water. These areas are called floodplains and coastal plains and can be extracted from geological maps. They indicate areas with a potential to flood in the future.

The Geological Indicators of Flooding Team have compared photographs from the flight with the new BGS Geological Indicators of Flooding Map. A comparison of the photograph and geological maps shows a correlation between areas which have flooded and areas marked as alluvial deposits (with a potential to flood).

Flooding of the River Nith in Dumfries.

More photographs and information on geology and flooding
Gallery

Areas of potential flooding of the River Nith in Dumfries - as shown (in blue) by the BGS Geological Indicators of Flooding Map. (Geological Indicators of Flooding map, British Geological Survey © NERC 2010. OS topography © Crown Copyright. All rights reserved. BGS 100017897/2009)

Flooding of the River Nith in Dumfries.

Comparison between the Geological Indicators of Flooding and the actual flood of the River Annan in November 2009. The dark blue represents deposits that indicate areas susceptible to flooding. The blue stipple indicates the slightly elevated deposits that would potentially be susceptible to flooding in more extreme or prolonged events.