BGS undertook an aerial survey of the Trent Valley flooding event on 9 November 2000. These photographs were used to establish a link between flooding and Geology.

To read the entire publication on this case study download the Earthwise issue: Modern geological mapping on page 25.
Gallery

Trent Valley flooding event in Gunthorpe, November 2000 (a 1-35-year magnitude event).The dry ground corresponds to river terrace outcrops on the geological map.

Simplified Quaternary geology of the River Trent floodplain around Gunthorpe, 9km east of Nottingham. The red square approximately denotes the area of the photograph, left. The blue square approximately denotes the area of the LiDAR image, right.

Airbone laser scan (LiDAR method) showing micro-topography and alluvial elements of the Trent floodplain for the southern part of the area shown in the geological map. 1 Gravel ridges, caused by northward meander migration; 2 Levee; 3 Flood basin (potential wetland); 4 Abandoned channel. River flow direction is towards the north-east.

Airborne laser scan (LiDAR method) showing micro-topography and alluvial elements of the Trent floodplain for the southern part of the area shown in the geological map.

This case study was the initiator for the creation of the Geological Indicators of Flooding dataset (GIF). The case study established that in detail, geological maps show that the floodplain corresponds to the extent of Alluvium, which represents the clay, silt, sand and gravel deposits laid down by fluvial activity (meander migration and flooding) related to the modern river channel (see LiDAR image). Many larger floodplains include additional areas of raised ground representing the 'first terrace' or the 'floodplain terrace', which is overlapped by the alluvium (see geological map).

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British Geological Survey
Keyworth
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