Geomorphology from Synthetic Aperture Radar (SAR) Coherence

Satellites carrying synthetic aperture radar (SAR) instrumentation are providing novel and exciting opporutnities to perform geomorphological analysis from space-bourn observations.

4-Year average Sentinel-1 coherence for our regions of interest in the Pocitos basin (left) and Quebrada del Toro (right) in northwestern Argentina.

In our recent paper Applications of SAR interferometric coherence time series: Spatiotemporal dynamics of geomorphic transitions in the south‐central Andes, we exploit ESA/Copernicus’s Sentinel-1 C-band SAR images to characterize geomorphic activity in the Central Andes of northwestern Argentina. We create a 4 year time-series of surface change from the coherence between SAR images taken 2-4 weeks apart, then calculate the average pattern of geomorphic chagne over these four years. Using the average coherence for the arid and semi-arid regions of our study area, we are able to estimate the transition between geomorphic/sediment transport domains (e.g., between areas dominated by gravity-driven hillslope erosion and by erosion from fluvial incision).

Example of the demarkation between hillslope, bedrock fluvial, and alluvial sediment transport domains for a small watershed in the Quebrada del Toro in northwestern Argentina.

Additionally, across regional rainfall and vegetation gradients, we observe a positive correlation between 10-Beryllium terrestrial cosmogenic nuclide derived basin-wide erosion rates and the basin-wise range of cohrence values. There is also a positive correlation between basin-wise coherence range and topometric proxies of longterm uplift and erosion (e.g., channel steepness). Our study suggests that a dense time series of interferometric coherence can be used as a proxy for surface sediment movement and landscape stability in vegetation‐free settings at event to decadal timescales.