LAHAR-MM: An integrated approach to LAhar Hazard Assessment and eaRly warning using geophysical Monitoring and numerical Modelling

Volcanic mudflows, or lahars, are one of the most dangerous, damaging and deadly volcanic hazards. These fast-moving flows of water-sediment mixtures are generated when unconsolidated volcanic deposits are mobilised by rain or other sources of surface water. They are unpredictable and energetic, have long runouts, and can mobilize large volumes of solid material and boulders. The largest events can be catastrophic, but even small and frequently recurring events have an adverse impact on communities, hampering their development and exacerbating social challenges. In many settings around the world, lahars are a frequent occurrence. Volcanic activity refreshes the supply of material that can be mobilized and seasonal rainfalls triggers these flows. Communities are forced to live while exposed to lahar hazards; simple avoidance is not feasible, so practical mitigations based on early detection and early warnings are essential to disaster risk reduction. In LAHAR-MM we plan to translate new scientific knowledge gained during the project into operational tools that will be integrated into existing lahar detection platforms, and thus, contribute to the next generation of lahar Early Warning Systems. Our understanding of the physical processes that control lahar dynamics remains limited. The two core scientific aims of this project are: 1) to understand the dynamics of rainfall-triggered lahars, from initiation to impact and emplacement; 2) to decipher the causative links between flow properties and flow regimes, and the seismic, deformation and acoustic fingerprints of lahars. This knowledge will underpin the delivery of a multi-disciplinary framework for real-time tracking and forecasting of lahar inundation. In short, our work will allow characterization of flow regimes and ahar properties based on their seismic (ground-shaking), deformation (ground tilt), and acoustic (low-frequency sound) signals. This will enable selection of previously calculated model scenarios of lahar propagation leading to near real-time predictions of flow arrival time, runout, and potential to cause damage. By creating new observational capabilities, coupled to development of novel physical models, we will generate new scientific understanding of lahar motion with immediate application in disaster risk reduction. Our deliverables will better inform hazard managers with relevant, scientifically robust, and observationally derived lahar predictions. We will collaborate with research partners in Guatemala, a country with high exposure to lahar hazards, but all outcomes, deliverables and new knowledge created and shared during this project will be readily transferrable to other lahar-prone regions worldwide. In Guatemala, we will integrate our results into an existing lahar detection system in partnership with local government agencies; with them we will co-design the framework for the integration of observations, predictive models, and hazard mapping to ensure immediate access to our research advances. This project will strengthen the resilience of communities vulnerable to lahar hazards by supporting evidence-based decision making and influencing the implementation of practical risk mitigation policies.