Geomorphic transport from historical shape from motion: Implications for
tropical and alpine environments
Abstract
Mountainous landscape evolution under tropical and alpine environments
is mainly dictated by climatic forcing which influences underlying
mechanisms of geomorphic transport (e.g., soil formation, river
dynamics, slope stability and mass wasting). The time scale over which
this influence acts ranges from seasonal to decennial time span. On the
seasonal time scale, for accessible locations and when manpower is
available, direct observations and field survey are the most useful and
standard approaches. While very limited studies have been focused on the
the decennial and century scale due to observational constrains. Here,
we present an open and reproducible pipeline based on historical aerial
images (up to 70yrs time span) that includes sensor calibration, dense
matching and elevation reconstruction over two areas of interest that
represent pristine examples for tropical and alpine environments: The
Rempart Canyon in Reunion Island, and the Bossons glacier in the French
Alps share a limited accessibility (in time and space) that can be
overcome only from remote-sensing. We reach unprecedented resolution:
the aero-triangulation falls at sub-metric scale based on ground truth,
which is comparable to the initial images spatial sampling. This
provides elevation time series with a better resolution to most recent
satellite images such as Pleiades. In the case of the Rempart Canyon, we
identified and quantified the results of 2 landslides that occurred in
1965 and 2001, and characterized the landslides dynamics. As for the
alpine case, we highlight the effect of the temperature plateau occurred
during 1939-1970 in Europe before the well known accelerated retreat
during the post-industrial period. In both cases, we emphasize the
strong effect of extreme events over multi-decennial to century
time-scales.