Assessing lahars from ice-capped volcanoes using ASTER satellite data, the SRTM DTM and two different flow models: case study on Iztaccíhuatl (Central Mexico)

Abstract

Abstract. Lahars frequently affect the slopes of ice-capped volcanoes. They can be triggered by volcano-ice interactions during eruptions but also by processes such as intense precipitation or by outbursts of glacial water bodies not directly related to eruptive activity. We use remote sensing, GIS and lahar models in combination with ground observations for an initial lahar hazard assessment on Iztaccíhuatl volcano (5230 m a.s.l.), considering also possible future developments of the glaciers on the volcano. Observations of the glacial extent are important for estimations of future hazard scenarios, especially in a rapidly changing tropical glacial environment. In this study, analysis of the glaciers on Iztaccíhuatl shows a dramatic retreat during the last 150 years: the glaciated area in 2007 corresponds to only 4% of the one in 1850 AD and the glaciers are expected to survive no later than the year 2020. Most of the glacial retreat is considered to be related to climate change but in-situ observations suggest also that geo-and hydrothermal heat flow at the summit-crater area can not be ruled out, as emphasized by fumarolic activity documented in a former study. However, development of crater lakes and englacial water reservoirs are supposed to be a more realistic scenario for lahar generation than sudden ice melting by rigorous volcano-ice interaction. Model calculations show that possible outburst floods have to be larger than ∼5×10 5 m 3 or to achieve an H/L ratio (Height/runout Length) of 0.2 and lower in order to reach the populated lower flanks. This threshold volume equals 2.4% melted ice of Iztaccíhuatl's total ice volume in 2007, assuming 40% water and 60% volumetric debris content of a potential lahar. The model sensitivity analysis reveals important effects of the generic type of the Digital Terrain ModelCorrespondence to: D. Schneider (demian.schneider@geo.uzh.ch) (DTM) used on the results. As a consequence, the predicted affected areas can vary significantly. For such hazard zonation, we therefore suggest the use of different types of DTMs and flow models, followed by a careful comparison and interpretation of the results.

Source to sink: A review of three decades of progress in the understanding of volcaniclastic processes, deposits, and hazards

“…Other workers are redeveloping lahar modelling codes from first principles to enable simulation of bulking and entrainment (Fagents and Baloga, 2006). All models are, however, sensitive to some input variable, be it channel resistance, basal or internal friction angle, or resolution of the digital elevation model (Stevens et al, 2002;Huggel et al, 2008;Schneider et al, 2008), so that iterative hind-casting of lahar events is more typical (and accurate) than a priori prediction. Such models have two main functions; a) development of prediction for flow behaviours to better inform hazard management through generating outputs such as arrival time, peak stage and sediment concentration at some downstream point of interest, and b) provision of mechanistic insights into flow behaviour, such as possible causes of vertical segregation or bed entrainment (Papa et al, 2004).…”

First approaches towards modelling glacial hazards in the Mount Cook region of New Zealand's Southern Alps

“…In addition, the New Zealand 25 m DTM is developed from 1986 aerial photography, and significant topographic changes have occurred within the glacial landscape over recent decades, most evidently surrounding the larger valley glaciers, where ice surfaces have lowered up to 4 m per year (Blair, 1994). Elevation data computed from ASTER stereo imagery or the 90 m resolution shuttle radar topography mission (SRTM) (Schneider et al, 2008), can keep pace with changing environmental conditions, but provide reduced topographic detail and can have severe errors in steep terrain. For more advanced numerical models, such as RAMMS, topographic sensitivity becomes more pronounced, and therefore a lack of recent high resolution elevation data from the Southern Alps remains a limiting factor in representing complex flow dynamics.…”

“…In addition, the MSF model has no physical basis, and therefore cannot represent more complex behavior of mass movements such as barrier run-up and overtopping. Despite these obvious limitations, the MSF model has proven a useful tool for early recognition of hazard potential, and is particularly well suited for use at larger spatial scales where multiple source areas are identified, and direct field observations may be difficult (e.g., Huggel et al, 2004;Schneider et al, 2008). As with previous studies, a worst-case scenario approach is used, whereby modelled flow paths are continued until a probable maximum runout is reached.…”

Runout and deposit morphology of Bingham fluid as a function of initial volume: implication for debris flow modelling

“…So, the results of those estimates are directly used in empirical models such as Laharz to reproduce the flow trajectory and maximum runout (Dávila et al 2007;Macias et al 2008;Schneider et al 2008;Muñoz-Salinas et al 2008;among others). If the empirical models give no information about velocity and poor information about flow depth, more sophisticated numerical models like Titan 2D , SPH (Pastor et al 2009b), or Dan 2D (Hungr 1995), among others, are used for this purpose.…”

“…Different values of the viscosity and yield stress have been proposed for different real events (Cola et al 2008;Naef et al 2006, among others). Numerical modelling has been used to extrapolate and apply these rheological properties to field observations in order to map landslide susceptibility and identify hazardous zones (Hubbard et al 2007;Macías et al 2008;Schneider et al 2008;Williams et al 2008 among others).…”