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Geographical information system approaches for hazard mapping of dilute lahars on Montserrat, West Indies |
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| Authors: | A R Darnell J Barclay R A Herd J C Phillips A A Lovett P Cole |
| Institution: | 1. School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK 2. School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol, BS8 1RJ, UK 3. Montserrat Volcano Observatory, Flemmings, Montserrat, West Indies 4. Seismic Research Centre, University of the West Indies, Trinidad and Tobago, WI |
| Abstract: | Many research tools for lahar hazard assessment have proved wholly unsuitable for practical application to an active volcanic system where field measurements are challenging to obtain. Two simple routing models, with minimal data demands and implemented in a geographical information system (GIS), were applied to dilute lahars originating from Soufrière Hills Volcano, Montserrat. Single-direction flow routing by path of steepest descent, commonly used for simulating normal stream-flow, was tested against LAHARZ, an established lahar model calibrated for debris flows, for ability to replicate the main flow routes. Comparing the ways in which these models capture observed changes, and how the different modelled paths deviate can also provide an indication of where dilute lahars, do not follow behaviour expected from single-phase flow models. Data were collected over two field seasons and provide (1) an overview of gross morphological change after one rainy season, (2) details of dominant channels at the time of measurement, and (3) order of magnitude estimates of individual flow volumes. Modelling results suggested both GIS-based predictive tools had associated benefits. Dominant flow routes observed in the field were generally well-predicted using the hydrological approach with a consideration of elevation error, while LAHARZ was comparatively more successful at mapping lahar dispersion and was better suited to long-term hazard assessment. This research suggests that end-member models can have utility for first-order dilute lahar hazard mapping. |
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