Cornwall: November 2010


A BGS response team flew over the St Austell area on 17 November 2010 during the flooding to find out how modern flooding compares to ancient flood areas.

BGS geologist, Elaine Burt, observed flooding from 300 m (1000 ft) from a helicopter; flying over one of the worst affected areas travelling south from Bodmin to Lostwithiel along the River Fowey.

The floodwater and several minor 'landslides' have caused widespread disruption to travel and people have been evacuated from their homes.

Flooded field with sheep next to the River Fowey near Bodmin Parkway Station.

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 floodwater. 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 will compare photographs from the flight over the next few days with the new BGS Geological Indicators of Flooding Map. A comparison of the photographs and geological maps shows a correlation between areas which have flooded and areas marked as alluvial deposits (with a potential to flood).

Landslides

A landslide is defined as a movement of a mass of rock, earth or debris down a slope.

Some of the 'landslides' reported in Cornwall may be collapsed embankments or due to debris-filled floodwater that has been washed onto roads. These sorts of mass movement aren't classified by the BGS as landslides.

The landslide reported outside of Luxulyan was surveyed from the air by a BGS geologist. The landslide occurred within a railway cutting in the weathered and jointed granite of the St Austell Intrusion. The landslide appears to be a combination of rock and debris falls triggered by intense rainfall. The landslide debris covered approximately 50 m of railway track resulting in the closure of the Newquay–Par branch line. Photographs during the survey are shown below (©BGS/NERC: photographer Graham Davies) .

What is a landslide and How does BGS classify landslides?

Comparison of photographs and geological maps

Golf course flooded by the River Fowey north of Lostwithiel
Lostwithiel Golf Course 1 Perspective

Contact Enquiries

Enquiries
British Geological Survey
Keyworth
Nottingham
NG12 5GG
E-mail: enquiries@bgs.ac.uk
Telephone: 0115 936 3143
Fax: 0115 936 3276