Coupling gravimetry and morphometry to quantify and localize mass transfers across scales in geomorphology
Abstract
Quantifying continental erosion brings valuable constraints on tectonics, climate or human activities, which all have
an active role in surface processes. This quantification is classically done through in-situ measurements of river
sediment discharge but often suffers from spatio-temporal scarcity. Here we show that temporal gravimetry, that is,
the integrative measure of mass changes through time, is an appropriate tool for such a quantification, at both local
and global scales, provided geometric constraints on the redistributed sediment are available. At the local scale,
we combined repeated terrestrial gravity and drone photogrammetry surveys, once a year in 2015, 2016 and 2017
over a 1-km2 area in central Taiwan featuring both a large river and a slow landslide. The good agreement between
gravity and terrain changes allowed us to retrieve the mass of sediment transiting locally in this area. At the global
scale, we take advantage of satellite gravimetry (GRACE), which has monitored gravity changes worldwide for 15
years. By coupling sedimentations zones estimates derived from sea currents model ECCO2 and GRACE satellite
data, we retrieved sediment fluxes consistent with in situ data offshore rivers with the largest sediment loads. At
the light of these experimental studies, the ongoing efforts to improve both gravimeters and geomorphometric data
open new perspectives in the field of quantitative geomorphology. In particular, key modern challenges such as
closing the budget between erosion and sedimentation or monitoring sand mining, a rising societal concern, could
be efficiently tackled by this interdisciplinary approach.