Abstract
Probabilistic quantification of lahar hazard is an important component of lahar risk assessment and mitigation. Here we propose a new approach to probabilistic lahar hazard assessment through coupling a lahar susceptibility model with a shallow-layer lahar flow model. Initial lahar volumes and their probabilities are quantified using the lahar susceptibility model which establishes a relationship between the volume of mobilised sediment and exceedance probabilities from rainfall intensity-frequency-duration curves. Rainfall-triggered lahar hazard zones can then be delineated probabilistically by using the mobilised volumes as an input into lahar flow models. While the applicability of this model is limited to rain-triggered lahars, this approach is able to reduce the reliance on historic and empirical estimates of lahar hazard and creates an opportunity for the generation of purely quantitative probabilistic lahar hazard maps. The new approach is demonstrated through the generation of probabilistic hazard maps for lahars originating from the Mangatoetoenui Glacier, Ruapehu volcano, New Zealand.
Highlights
Probabilistic quantification of lahar hazard is an important component of lahar risk assessment and mitigation
Study area and simulation inputs The process outlined in the previous section is demonstrated through the generation of probabilistic hazard maps for lahars originating from the Mangatoetoenui Glacier, Ruapehu volcano, New Zealand
The probabilistic lahar hazard maps generated here by combining numerical modelling with initial volumes determined through the susceptibility approach of Mead et al (2016) have demonstrated a potential methodology for probabilistic hazard mapping of lahars
Summary
Probabilistic quantification of lahar hazard is an important component of lahar risk assessment and mitigation. We propose a new approach to probabilistic lahar hazard assessment through coupling a lahar susceptibility model with a shallow-layer lahar flow model. Lahar hazard assessments typically provide this information in the form of hazard maps quantifying the probability and extent of potential lahars to varying degrees (Calder et al 2015). The potential of coupling lahar susceptibility model outputs to lahar flow model inputs in order to quantify lahar hazard probabilistically was discussed, but not demonstrated. Outputs of the combined model in the form of probabilistic hazard maps are demonstrated for lahar scenarios originating from Mangatoetoenui Glacier, Mt. Ruapehu, New Zealand. This work is intended to demonstrate an approach for probabilistic estimates of lahar hazard and highlight areas of research needed to enhance the reliability of these hazard estimates
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