River sediment dynamics in high relief landscape from shape from motion

The evolution of landscapes with steep slopes and subject to tropical or alpine climates is mainly controlled by several mechanisms of geomorphic transport such as soil formation, river dynamics, slope stability and mass wasting. The time scale over which the climate influence acts on these mechanisms 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 decennial and century scale due to observational constrains. Here, we present a reproducible workflow based on historical aerial images (up to ~70yrs time span) that includes sensor internal calibration and external orientation, 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 Arveyron river in the French Alps share a limited accessibility (in time and space) that can be overcome only from archive remote-sensing observations. 

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 river sediment transdport we emphasize similar tracking for the alpine case, which is controlled by glacial dynamics.  In both cases, we emphasize the strong effect of climatic forcing (precipitation and temperature) over multi-decennial to century time-scales.