Abstract
The Volcán de Colima, one of the most active volcanoes in Mexico, is
commonly affected by tropical rains related to hurricanes that form over the
Pacific Ocean. In 2011, 2013 and 2015 hurricanes Jova, Manuel and Patricia,
respectively, triggered tropical storms that deposited up to 400 mm of rain in
36 h, with maximum intensities of 50 mm h −1. The effects were devastating, with
the formation of multiple lahars along La Lumbre and Montegrande ravines,
which are the most active channels in sediment delivery on the south-southwest flank of
the volcano. Deep erosion along the river channels and several marginal
landslides were observed, and the arrival of block-rich flow fronts resulted
in damages to bridges and paved roads in the distal reaches of the ravines.
The temporal sequence of these flow events is reconstructed and analyzed
using monitoring data (including video images, seismic records and rainfall
data) with respect to the rainfall characteristics and the hydrologic
response of the watersheds based on rainfall-runoff numerical simulation. For
the studied events, lahars occurred 5–6 h after the onset of rainfall,
lasted several hours and were characterized by several pulses with block-rich
fronts and a maximum flow discharge of 900 m3 s −1. Rainfall-runoff
simulations were performer using the SCS-curve number and the Green–Ampt
infiltration models, providing a similar result in the detection of simulated maximum
watershed peaks discharge. Results show different behavior for the arrival
times of the first lahar pulses that correlate with the simulated catchment's
peak discharge for La Lumbre ravine and with the peaks in rainfall intensity
for Montegrande ravine. This different behavior is related to the area and
shape of the two watersheds. Nevertheless, in all analyzed cases, the largest
lahar pulse always corresponds with the last one and correlates with the
simulated maximum peak discharge of these catchments. Data presented here
show that flow pulses within a lahar are not randomly distributed in time,
and they can be correlated with rainfall peak intensity and/or watershed
discharge, depending on the watershed area and shape. This outcome has
important implications for hazard assessment during extreme
hydro-meteorological events, as it could help in providing real-time
alerts. A theoretical rainfall distribution curve was designed for Volcán
de Colima based on the rainfall and time distribution of hurricanes Manuel and
Patricia. This can be used to run simulations using weather forecasts prior
to the actual event, in order to estimate the arrival time of main lahar
pulses, usually characterized by block-rich fronts, which are responsible for
most of the damage to infrastructure and loss of goods and lives.
Citation
ID:
224371
Ref Key:
capra2018naturalhydrological