After The 2017 Disaster: Villa Santa Lucia And Its Surrounding Glaciers.
A Contribution To Resilience From A Glaciological View At Chilean
Northern Patagonia.
Abstract
On 16 December 2017 a chain mass movement, started as a rockslide,
produced a debris and mud flow which channelized in the Burritos River.
The flow reached and flooded the Santa Lucia village (-43.41°/-72.37°)
destroying 50% of the urban area and killing 22 people. This fatal
event resulted as a conjunction of geologic, meteorological and
glaciological variables: Highly altered volcanic rocks with deep
vertical fractures and steep slopes in the Yelcho Range; an intense
precipitation event 30 hours prior the rockslide of up to 124.8 mm in
one day with a high zero-degree isotherm elevation; an ice-cored lateral
moraine deposit under the headwall plus hyper saturated soils downhill
near the Burritos River. The role of a proglacial lake has been
discussed, nonetheless, current studies argue that the main liquid
inputs could have been pre-existing water in saturated soil. In this
study we analyzed satellite imagery available on the web, including
Sentinel 2 and Landsat scenes. Based on the Public Chilean Glacier
Inventory, we quantify the retreat of glaciers laying on the eastern
flank of the Yelcho Range, west of the Santa Lucía village. On a
time-span of 33 years (1987 to 2020), we estimate over 650 m of glacial
retreat plus an accelerated retreat rate up to 30 m/yr for the last
decade. Such glacier shrinkage coupled with increasing local
temperatures may lead to the genesis of more proglacial lakes, enhancing
the odds of chain mass movements, favoring the interaction between
rockslides and glacial lakes. Our results show an example of a
relatively simple analysis that can be performed with basic tools and
with no further expenses. The proper understanding of glacial landscape
evolution with time and its response to extreme climatic events is
essential to prevent human loses, as these events will be more frequent
due to the current climate change context. For that purpose, further
work aims to clarify more hidden variables in the region, such as the
number of proglacial lakes, steep slopes on headwalls, highly eroded
slopes, among others, in order to enlarge the local knowledge linked to
one of many components involved on a natural disaster, thus, increasing
the resilience of communities whom are still occupying the affected area
after the Santa Lucía landslide disaster.