Accreting, fast and slow: Geometry, kinematics and sediment load of fluvial channels

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Presenter

Zoltán Sylvester, Ph.D.
Research Professor
Bureau of Economic Geology
Dept. of Earth and Planetary Sciences
The University of Texas at Austin

Description

Although satellite imagery is increasingly used to study river mobility, two challenges remain: (1) fast, accurate tracking of channel banks and centerlines, and (2) linking these observations to predictive models and stratigraphic architecture. We developed ‘rivabar,’ a graph-based Python tool that automatically extracts centerlines and banklines. Using ‘rivabar’ on time-lapse Landsat and Planet Labs imagery, we visualize the evolution of single-thread and multi-thread rivers and investigate how well simple models predict channel migration. In single thread rivers with low sediment loads, curvature-based models predict migration rates well, and the stratigraphy of the point bars is relatively simple. In contrast, high sediment loads result in the rapid growth of bars that are accreted to the inner bank; the resulting stratigraphy is more complicated, and simple curvature-based models of meandering are less predictive. Predicting channel movement in multi-thread rivers is even more challenging. However, preliminary results show that the upstream sides of mid-channel bars typically erode and migrate downstream, while the downstream sides grow irregularly. These observations suggest that sediment load is an important driver of stratigraphic complexity. Our automated mapping approach offers a scalable way to better understand channel mobility and stratigraphic complexity from widely available remote sensing data.