Linking landslide patterns to transient landscapes in the northern
Colombian Andes
Abstract
Landslides are among the most recognizable evidence of hillslope erosion
in tectonically active mountains. Yet, how much of the distribution of
landslides of different ages relates to, or inherits from, the pattern
of topographic metrics of landscape evolution remains partially
unresolved, and especially so in tropical areas. We derive such metrics
for 650 catchments, including their mean hypsometric integral, local
relief, geological lineament, density, and stepness variations and
knickpoint density of river channels as proxies of tectonic activity; we
test how these proxies match with, if not explain, the distribution of
some 14,000 prehistoric and modern landslides in the Colombian Andes. A
$K$-means cluster analysis of catchment hypsometry reveals four
distinct groups of catchments. We interpret these groups to reflect
different states of transience with clear contrasts in mean local
relief, average hillslope inclination, channel steepness, and landslide
density. We propose that tectonic uplift, base-level changes, and
passing waves of incision control these different states of transience.
Yet, we find that landslides occur widely without much spatial
association to, or amassing near, major channel knickpoints. This
observation reflects what we would expect from a threshold landscape in
which landslides abound irrespective of contrasts in local river
incision rates. Still, we notice a pronounced attraction of landslides
to transient divides, where especially prehistoric landslides are
preferentially preserved. We infer that, in our study area at least,
differences in catchment hypsometry might be more useful to track
potential tectonic controls on landslide patterns than comparing these
to knickpoint distributions or channel metrics.