Artículo de revista
Lahar simulation at active volcanoes of the Southern Andes: implications for hazard assessment
Fecha
2015Registro en:
Nat Hazards (2015) 77:693–716
1573-0840
DOI: 10.1007/s11069-015-1617-x
Autor
Castruccio Álvarez, Angelo
Clavero, Jorge
Institución
Resumen
Lahars are catastrophic events that have the potential to cause the loss of life
and damage to infrastructure over inhabited areas. Consequently the zoning of associated
hazards is a critical task. We evaluated the lahar hazards at two volcanoes of the Southern
Volcanic Zone of the Andes of Chile: Villarrica and Calbuco. We applied the LAHARZ
and MSF codes using three DEMs: SRTM, ASTER GDEM and a topographic map-derived
DEM to evaluate whether low-resolution and widely available DEMs are suitable for
modelling lahars. Our results indicate that the original 0.05 calibration constant used in the
original global LAHARZ model to calculate the cross-sectional area of inundation is not
adequate for lahars from these volcanoes, and our analyses suggest a value of 0.02 as a
more appropriate value. One of the most important results obtained is the high relevance
that simulating topographic changes for multi-pulses lahar events has. The simulations
indicate that dramatic changes in trajectories could occur during such scenarios, and areas
not recognized as susceptible of being affected by lahars using the original topography can
also be affected. These results have important implications for hazard assessment, as for
example, the town of Puco´n, located 16 km to the N of the Villarrica volcano was not
recognized to be located in inundation areas when using LAHARZ on the original
topography represented by unmodified DEMs. However, more than 50 % of the town
could be inundated if lahars are modelled as multiple pulses, in agreement with geological
and historical observations, as well as results shown on previous hazard maps. The MSF
code better simulates the lateral extension of possible lahars, especially over flat areas or where topography is complex with many stream trajectories, but lacking a reliable method
to determine the run-out distance. Our results indicate that the modifications made to the
LAHARZ governing equations give very good results for assessing the hazards associated
with lahars in volcanoes of this region of the Andes.