The chronology and the hydrometeorology of catastrophic floods on Dartmoor, South West England

Authors

  • S. A. Foulds,

    Corresponding author
    1. Institute of Geography and Earth Sciences, Llandinam Building, Aberystwyth University, Aberystwyth, Wales, UK
    • Correspondence to: S. A. Foulds, Institute of Geography and Earth Sciences, Llandinam Building, Aberystwyth University, Aberystwyth, SY23 3DB Wales, UK

      E-mail: sif3@aber.ac.uk

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  • M. G. Macklin,

    1. Institute of Geography and Earth Sciences, Llandinam Building, Aberystwyth University, Aberystwyth, Wales, UK
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  • P. A. Brewer

    1. Institute of Geography and Earth Sciences, Llandinam Building, Aberystwyth University, Aberystwyth, Wales, UK
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Abstract

Extreme floods are the most widespread and often the most fatal type of natural hazard experienced in Europe, particularly in upland and mountainous areas. These ‘flash flood’ type events are particularly dangerous because extreme rainfall totals in a short space of time can lead to very high flow velocities and little or no time for flood warning. Given the danger posed by extreme floods, there are concerns that catastrophic hydrometeorological events could become more frequent in a warming world. However, analysis of longer term flood frequency is often limited by the use of short instrumental flow records (last 30–40 years) that do not adequately cover alternating flood-rich and flood-poor periods over the last 2 to 3 centuries. In contrast, this research extends the upland flood series of South West England (Dartmoor) back to ca AD 1800 using lichenometry. Results show that the period 1820 to mid-1940s was characterized by widespread flooding, with particularly large and frequent events in the mid-to-late 19th and early 20th centuries. Since ca 1850 to 1900, there has been a general decline in flood magnitude that was particularly marked after the 1930s/mid-1940s. Local meteorological records show that: (1) historical flood-rich periods on Dartmoor were associated with high annual, seasonal and daily rainfall totals in the last quarter of the 19th century and between 1910 and 1946, related to sub-decadal variability of the North Atlantic Oscillation and receipt of cyclonic and southerly weather types over the southwest peninsula; and (2) the incidence of heavy daily rainfall declined notably after 1946, similar to sedimentary archives of flooding. The peak period of flooding on Dartmoor predates the beginning of gauged flow records, which has practical implications for understanding and managing flood risk on rivers that drain Dartmoor. Copyright © 2013 John Wiley & Sons, Ltd.

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