Autogenic Controls on River Bank Migration; the Trinity River, TX
Abstract
Comparison of two time-lapse airborne lidar maps of 30 successive river bends the lower Trinity River in TX, USA, shows an interesting shift in river-bend kinematics. The initial time-lapse map covering the period between 2011 and 2015 shows a greater amount of deposition on point bars and erosion along the outer bank of bends than the period between 2015 and 2017, despite an almost doubling of days under flood conditions in the later interval (146 vs. 76 days). Tops of point bars that had experienced up to 1.5 m of vertical aggradation during the flooding between 2011 and 2015 were subsequently eroded back down to almost their initial elevation. The relative lateral movement of the point bars versus the outer banks of bends for the later interval cancelled out the changes in bar-to-bank width that occurred during the first interval. For the 2011 - 2015 interval, river bends along the upstream half of the study reach narrowed by an average of 2.2 m and widened along the downstream half of the reach by an average of 1.4 m. The period between 2015 and 2017 resulted in a subsequent widening of bends within the upstream reach by an average of 2.4 m and a narrowing along the downstream reach of 0.6 m; causing the overall amount of change to total an average of only 1% in the functional bar-to-bank width of the channel. Results suggest that the behavior of the river channel is dependent on the state of the channel at the beginning of the observation period, ultimately implying that autogenic controls can be more important than allogenic controls in determining the response of a river channel to different discharge events.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMEP11E2102M
- Keywords:
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- 1821 Floods;
- HYDROLOGYDE: 1825 Geomorphology: fluvial;
- HYDROLOGYDE: 4327 Resilience;
- NATURAL HAZARDSDE: 4328 Risk;
- NATURAL HAZARDS