Estimating building vulnerability to volcanic ash fall for insurance and other purposes

Abstract

Volcanic ash falls are one of the most widespread and frequent volcanic hazards, and are produced by all explosive volcanic eruptions. Ash falls are arguably the most disruptive volcanic hazard because of their ability to affect large areas and to impact a wide range of assets, even at relatively small thicknesses. From an insurance perspective, the most valuable insured assets are buildings. Ash fall vulnerability curves or functions, which relate the magnitude of ash fall to likely damage, are the most developed for buildings, although there have been important recent advances for agriculture and infrastructure. In this paper, we focus on existing vulnerability functions developed for volcanic ash fall impact on buildings, and apply them to a hypothetical building portfolio impacted by a modernday Tambora 1815 eruption scenario. We compare and contrast the different developed functions and discuss some of the issues surrounding estimation of potential building damage following a volcanic eruption. We found substantial variability in the different vulnerability estimates, which contribute to large uncertainties when estimating potential building damage and loss. Given the lack of detailed and published studies of building damage resulting from ash fall this is not surprising, although it also appears to be the case for other natural hazards for which there are far more empirical damage data. Notwithstanding the potential limitations of some empirical data in constraining vulnerability functions, efforts are required to improve our estimates of building damage under ash fall loading through the collection of damage data, experimental testing and perhaps theoretical failure analysis. For insurance purposes, the current building typologies provided for use with vulnerability functions are too detailed to map to the relatively limited information on building types that is typically available to insurers. Thus, efforts to provide vulnerability functions that can be used where only limited information is available regarding building types would also be valuable, both for insurers and for at-risk areas that have not been subject to detailed building vulnerability surveys.

Design of parametric risk transfer solutions for volcanic eruptions: an application to Japanese volcanoes

“…a defined combination of construction type, building rise, and roof pitch) the model uses a specific vulnerability function that computes the probability of experiencing a certain level of damage (expressed as a damage ratio of cost of repair versus total cost of replacement) for a given physical load value upon that structure. The vulnerability functions were developed on the basis of several studies on the subject (Spence et al, 2005;Maqsood et al, 2014;Jenkins et al, 2014a, b;Blong et al, 2017a) for building typologies common in the area (see Table 2). Given the lack of data on roof type for individual structures, the model assumes probabilities of different roof types within the exposure set (low, medium, or high pitch) depending on the building occupancy, construction typology and building rise.…”

Remotely assessing tephra fall building damage and vulnerability: Kelud Volcano, Indonesia

“…Past research on forecasting tephra fall impacts to buildings and all previously developed fragility curves, placed a focus on identifying loads likely to cause severe roof or building collapse, driven by life-safety concerns (Spence et al, 2005;Zuccaro et al, 2008;Jenkins and Spence, 2009). In any given tephra fall however, exponential thinning with distance means that light tephra falls cover a relatively large area and therefore buildings receiving relatively light damage are likely to far outnumber collapses (Blong et al, 2017b), as was the case in the Kelud 2014 eruption. In cases such as this, repair costs associated with non-collapse damage might contribute substantially to the total cost of recovery, so it is important for future studies of tephra fall impacts to buildings to determine under what hazard intensities relatively lightmoderate damage occurs.…”

Design of parametric risk transfer solutions for volcanic eruptions: an application to Japanese volcanoes

“…a defined combination of construction type, building rise and roof pitch) the model uses a specific vulnerability function that computes the probability of experiencing a certain level of damage (expressed as a damage ratio of cost of repair versus total cost of replacement) for a given physical load value upon that structure. The vulnerability functions were developed on the basis of several studies on the subject (Spence et al;2005;Maqsood et al, 2014;Jenkins et al, 2014;Jenkins et al, 2015;Blong et al, 2017) for building typologies common in the area (see Table 2). Given the lack of data on roof type for individual structures, the model assumes probabilities of different roof types within the exposure set (low, medium or high pitch) depending on the building occupancy, construction typology and building rise.…”