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  3. Philippines - Quantitative Lahar Impact and Loss Assessment under changing Land Use and Climate Scenarios

UK - Department for Business, Energy and Industrial Strategy

Philippines - Quantitative Lahar Impact and Loss Assessment under changing Land Use and Climate Scenarios

Disclaimer: The data for this page has been produced from IATI data published by UK - Department for Business, Energy and Industrial Strategy. Please contact them (Show Email Address) if you have any questions about their data.

Project Data Last Updated: 27/08/2020

IATI Identifier: GB-GOV-13-FUND--Newton-NE_S00274X_1

Description

Lahars are volcanic mudflows that often occur during and after volcanic eruptions when ash deposited from the volcano is remobilized by rainfall. Lahars are a major hazard to people, often resulting in fatalities and displacement of communities. Lahars are a particular hazard in the Philippines due to the large number of volcanoes that erupt explosively and the tropical climate. The aim of this proposal is to develop an integrated, coherent model of lahars from their generation in catchments on volcanic flanks to their impacts on the build environment. This study has been co-developed between the University of Bristol and the Philippines Institute of Volcanology and Seismology (PHIVOLCS) during an active volcanic crisis in the Philippines, with Mt Mayon erupting and producing lahars. The project will advance lahar hazard assessment through the development of susceptibility and impact mapping, where the impacts are inferred from a convolution of predictions of lahar inundation and damage. The proposal will develop a new collaboration between UK and Philippines partners, based on combining expertise in hydrological and hazard modelling, sedimentology, geomorphology and hydrogeology. Our study will develop new and apply new models for the hydrology of catchments with recent ash deposits, informed by field studies of these environments conducted in the Philippines. This will allow rainfall forecasts to be propagated into lahar source conditions, including under future climate and land use settings. The catchment hydrology will be linked to a model of lahar motion, to allow the assessment of lahar inundation and the physical impacts in urban areas further from the volcano. We will apply the dynamic model at high resolution to provide predictions of lahar motion on the building scale. New mathematical modelling on the impacts of lahars on structure will provide methodology for assessing the physical vulnerability of the build environment to lahars. This integrated approach will allow, for the first time, a comprehensive assessment of the lahar hazards across a range of scales, providing the basis of future quantification of lahar risk, and will support the design of early warning systems. The project will provide advances in capacity for lahar hazard assessment in the Philippines and in other tropical countries with active volcanoes, and in dynamic aspects of risk related to hydrometeorological hazards, climate change, urbanization and land use change. Case study locations have been chosen to provide a combination of changing exposure due to climate and land use changes, and in rural and peri-urban settings.

Objectives

Assessing the risk communities face to lahar hazards requires an integrated modelling approach that accounts for the interactions of hydrometeorological conditions, land use characteristics, flow dynamics, and the build environment. Our aim is to develop a lahar model that is capable of predicting the lahar hazard footprint and the physical vulnerability of buildings to lahar impacts and this will be achieved through six linked objectives, co-developed and co-delivered by the University of Bristol and the Philippines Institute of Volcanology and Seismology. Objective 1: Predictive lahar model implementation at building scale. We will develop our dynamic model of lahars to efficiently predict flow dynamics on a range of scales, including, critically, on the scale of buildings, using automated mesh-refinement and interpolation schemes to connect wide-area low-resolution and local high-resolution topographic data. Objective 2: Linking Land Use and erodibility for lahar modelling. We will use fieldwork (ground surveys, UAVs, satellite observations) to examine land use in catchments and around channels, to characterise surface characteristics and the availability of erodible material (depth of erodible layers and ease of mobilization) and assess temporal changes to erodibility over days/weeks/months/years after an eruption. Objective 3: Catchment hydrology modelling for lahar initiation. We will develop a simplified but applicable model of catchment hydrology, accounting for infiltration, run-off and erosion, to determine potential volumes and estimate lahar hydrographs in drainage channels, linking the lahar initiation to rainfall across catchments. Objective 4: Characterising rainfall on catchment scale for lahar initiation under current and future climates. We will analyse rainfall data at the catchment scale for past and current lahar events and use flow observations and coincident rainfall and river stage data to characterise lahar triggering conditions and to calibrate catchment hydrology models. We will use these approaches to explore intensity and likelihood of future lahars under changing climate conditions. Objective 5: Using models to assess physical vulnerability. We will combine outputs of high-resolution modelling with new analysis of transient and quasi-steady impacts of lahars and their transported solid loads, to translate flow conditions to assessment of infrastructure vulnerability and loss estimation. Objective 6 Lahar Risk Assessment Test Case. We will integrate flow and hydrological modelling of footprints into spatial mapping of impacts and losses, with a comprehensive characterisation of the uncertainty in these predictions. We will work with local stakeholders (risk managers/civil defence, authorities and communities) to develop practical tools for assessing and communicating lahar threats and apply these to lahars from the ongoing eruption of Mayon. Objective 1 allows our lahar model to be used efficiently for hazard planning and response from the source region and into urban centres. Objective 2 provides the observational data necessary to determine the potential for lahar initiation across land use and precipitation conditions. Objective 3 allows rainfall observations and predictions to be translated into lahar source characteristics. Objective 4 provides data for calibrating the catchment model and for future-proofing the modelling under changing climate and land use. Objective 5 allows the translation of predictions of the dynamical characteristics of lahars into the physical vulnerability of structures. Objective 6 provide a stringent and encompassing test of the modelling framework and demonstrates the practical application for lahar hazard and risk.

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