Challenges of modeling current very large lahars at Nevado del Huila Volcano, Colombia

Abstract

Nevado del Huila, a glacier-covered volcano in the South of Colombia's Cordillera Central, had not experienced any historical eruptions before 2007. In 2007 and 2008, the volcano erupted with phreatic and phreatomagmatic events which produced lahars with flow volumes of up to about 300 million m 3 causing severe damage to infrastructure and loss of lives. The magnitude of these lahars and the prevailing potential for similar or even larger events, poses significant hazards to local people and makes appropriate modeling a real challenge. In this study, we analyze the recent lahars to better understand the main processes and then model possible scenarios for future events. We used lahar inundation depths, travel duration, and flow deposits to constrain the dimensions of the 2007 event and applied LAHARZ and FLO-2D for lahar modeling. Measured hydrographs, geophone seismic sensor data and calculated peak discharges served as input data for the reconstruction of flow hydrographs and for calibration of the models. For model validation, results were compared with field data collected along the Páez and Simbola Rivers. Based on the results of the 2007 lahar simulation, we modeled lahar scenarios with volumes between 300 million and 1 billion m 3 . The approach presented here represents a feasible solution for modeling high-magnitude flows like lahars and allows an assessment of potential future events and related consequences for population centers downstream of Nevado del Huila.

Risk estimation for future glacier lake outburst floods based on local land-use changes

“…Osti and Egashira, 2009;Worni et al, 2012). Studies on the assessment of local-scale hazards from floods from future lakes are currently a research gap.…”

“…To more accurately estimate the spatial distribution of the outburst flood and the aggregated inundation intensities, numerical models have been proved useful in several case studies (Osti and Egashira, 2009;Worni et al, 2012). First rough-scale modelling of outburst floods have already been performed for future lakes in Switzerland (Frey et al, 2010), but there is a lack of assessment of future damage potential and related risks of GLOFs.…”

A risk analysis for floods and lahars: case study in the Cordillera Central of Colombia

“…We assessed the pressure (p) by multiplying the flow density (q) with the squared flow velocity (v 2 ). Flow velocities of lahars of 5 to 15 m/s are reported for the Combeima river (Cepeda and Murcia 1998) and at comparable sites at Nevado del Huila (Worni et al 2012) and Nevado del Ruiz, Colombia (Verstappen 1992;Pierson 1995). Based on that, we set flow velocity at 10 m/s for lahars, and 4 m/s for floods, based on estimates from recent flood events.…”

“…In Colombia, the 1985 Nevado del Ruiz and Armero disaster is most well known (Pierson et al 1990;Thouret 1990). More recently, eruptions of the ice-covered Nevado del Huila volcano in 2007 and 2008 resulted in extremely large volcanic debris flows (lahars) with volumes in the range of tens to hundreds of millions cubic metres (Worni et al 2012).…”

The use of FLO2D numerical code in lahar hazard evaluation at Popocatépetl volcano: a 2001 lahar scenario

“…Misinterpretation of lahar deposits, including their magnitude and recurrence, could lead to exclusion of some areas that could be affected during major events. In recent years, one of the major instruments used to replicate old events and accurately delineate lahar active paths is lahar modeling (i.e., Iverson et al, 1998;Davila et al, 2007;Muñoz-Salinas et al, 2009a;Williams et al, 2008;Worni et al, 2012). Different simulations codes include LaharZ (Schilling, 1998), Titan2D two-phase flow (Williams et al, 2008), andFLO2D (O'Brien et al, 1993).…”