Predicting the Planform Configuration of the Braided Toklat River, Alaska, With a Suite of Rule-Based Models


  • Charles J.P. Podolak

    1. Hydrologist, U.S. Geological Survey, Anchorage, Alaska 99508; currently, Postdoctoral Associate, Nicholas School of the Environment, Duke University, Box 90328, Durham, North Carolina 27708-0328
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  • Paper No. JAWRA-12-0047-P of the Journal of the American Water Resources Association (JAWRA). Discussions are open until six months from print publication.



Abstract:  An ensemble of rule-based models was constructed to assess possible future braided river planform configurations for the Toklat River in Denali National Park and Preserve, Alaska. This approach combined an analysis of large-scale influences on stability with several reduced-complexity models to produce the predictions at a practical level for managers concerned about the persistence of bank erosion while acknowledging the great uncertainty in any landscape prediction. First, a model of confluence angles reproduced observed angles of a major confluence, but showed limited susceptibility to a major rearrangement of the channel planform downstream. Second, a probabilistic map of channel locations was created with a two-parameter channel avulsion model. The predicted channel belt location was concentrated in the same area as the current channel belt. Finally, a suite of valley-scale channel and braid plain characteristics were extracted from a light detection and ranging (LiDAR)-derived surface. The characteristics demonstrated large-scale stabilizing topographic influences on channel planform. The combination of independent analyses increased confidence in the conclusion that the Toklat River braided planform is a dynamically stable system due to large and persistent valley-scale influences, and that a range of avulsive perturbations are likely to result in a relatively unchanged planform configuration in the short term.