Sediment-charged flash floods on Montserrat: The influence of synchronous tephra fall and varying extent of vegetation damage

Alexander, J, Barclay, J, Susnik, J, Loughlin, SC, Herd, R, Darnell, A and Crosweller, S (2010) Sediment-charged flash floods on Montserrat: The influence of synchronous tephra fall and varying extent of vegetation damage. Journal of Volcanology and Geothermal Research, 194 (4). pp. 127-138.

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Abstract

On 20th May 2006 the Soufrière Hills Volcano on the Caribbean island of Montserrat experienced a large dome collapse and intense rainfall generated flash floods. The floods had very high loads of volcanic debris derived both from this and previous eruptions and can thus be classified as lahars. The floods reached unusually high water levels and caused substantial geomorphic change in the Belham Valley. Detailed rainfall and geomorphological data, coupled with the precise timing of events and yewitness accounts have facilitated an assessment of the relative importance of rainfall volume and intensity, older volcanic debris, pre- and syn-flood tephra fall and the extent of pre-flood vegetation damage for the behavior of this and subsequent sediment-laden floods in this setting. The change in runoff behavior was controlled by preexisting vegetation damage and synchronous tephra fall and this was critically important in controlling the impact of these flash floods. Although rainfall intensity and volume have some control on flood occurrence they are not the critical control on flash flood impact on the geomorphology in the Belham Valley. A significant conclusion of this study is that the extreme nature of the flash floods was not caused by extreme rainfall (as is commonly believed to be the primary cause of flash floods) but rather it was the result of changed runoff behaviour caused by the widespread syn-flood tephra deposition and importantly the widespread vegetation damage by volcanic-associated acid rain in the preceding weeks.

Item Type: Article
Faculty \ School: Faculty of Science > School of Environmental Sciences
University of East Anglia > Faculty of Science > Research Centres > Centre for Social and Economic Research on the Global Environment (CSERGE)
University of East Anglia > Faculty of Science > Research Groups > Resources, Sustainability and Governance
University of East Anglia > Faculty of Science > Research Groups > Environmental Earth Sciences
University of East Anglia > Faculty of Science > Research Groups > Volcanoes@UEA
University of East Anglia > Faculty of Science > Research Groups > Geosciences and Natural Hazards
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Depositing User: Rosie Cullington
Date Deposited: 28 Jan 2011 13:45
Last Modified: 25 Jul 2018 04:15
URI: https://ueaeprints.uea.ac.uk/id/eprint/20221
DOI: 10.1016/j.jvolgeores.2010.05.002

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