Island Formation Resulting From Radially Symmetric Flow Expansion
Abstract
Island formation and distributary channel branching are important processes in prograding river deltas. In this study, we develop and test a new theory predicting the distance to islands and channel bifurcations based on fluid mass conservation and radially symmetric transport conditions. We analyze channelization and island formation using nine new and five existing delta experiments as well as four field deltas. The new experiments were designed to produce islands from initial deposition of a mouth bar. Before island formation, each bar evolved into a radially symmetric deposit with unchannelized flow over its top previously described as a topographic flow expansion. This morphology was stable to topographic perturbations, and its distal limit prograded basinward while maintaining a characteristic flow depth. Island formation and channel branching occurred on top of this deposit. We hypothesize that this distance (Ψ) is set by the location where boundary shear stress applied by expanding, radially averaged flow falls below the threshold of sediment motion. The model predicts that the distance to the first island scales with water discharge, scales inversely with flow depth, and scales with the inverse square root of median grain diameter. Finally, from experiment to field scales, distances to island locations are predictedmore »
- Authors:
-
[1];
[2];
[3]
- Univ. of Arkansas, Fayetteville, AR (United States)
- Univ. of Wyoming, Laramie, WY (United States); Univ. of Texas, Austin, TX (United States)
- Univ. of Wyoming, Laramie, WY (United States)
- Publication Date:
- Research Org.:
- Univ. of Arkansas, Fayetteville, AR (United States)
- Sponsoring Org.:
- USDOE
- OSTI Identifier:
- 1512957
- Alternate Identifier(s):
- OSTI ID: 1422632
- Grant/Contract Number:
- SC0016163
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Journal of Geophysical Research. Earth Surface
- Additional Journal Information:
- Journal Volume: 123; Journal Issue: 2; Journal ID: ISSN 2169-9003
- Publisher:
- American Geophysical Union
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 58 GEOSCIENCES; delta; island; mouth bar; jet; coast; flow expansion
Citation Formats
Shaw, John B., Miller, Kimberly, and McElroy, Brandon. Island Formation Resulting From Radially Symmetric Flow Expansion. United States: N. p., 2018.
Web. doi:10.1002/2017jf004464.
Shaw, John B., Miller, Kimberly, & McElroy, Brandon. Island Formation Resulting From Radially Symmetric Flow Expansion. United States. doi:10.1002/2017jf004464.
Shaw, John B., Miller, Kimberly, and McElroy, Brandon. Thu .
"Island Formation Resulting From Radially Symmetric Flow Expansion". United States. doi:10.1002/2017jf004464. https://www.osti.gov/servlets/purl/1512957.
@article{osti_1512957,
title = {Island Formation Resulting From Radially Symmetric Flow Expansion},
author = {Shaw, John B. and Miller, Kimberly and McElroy, Brandon},
abstractNote = {Island formation and distributary channel branching are important processes in prograding river deltas. In this study, we develop and test a new theory predicting the distance to islands and channel bifurcations based on fluid mass conservation and radially symmetric transport conditions. We analyze channelization and island formation using nine new and five existing delta experiments as well as four field deltas. The new experiments were designed to produce islands from initial deposition of a mouth bar. Before island formation, each bar evolved into a radially symmetric deposit with unchannelized flow over its top previously described as a topographic flow expansion. This morphology was stable to topographic perturbations, and its distal limit prograded basinward while maintaining a characteristic flow depth. Island formation and channel branching occurred on top of this deposit. We hypothesize that this distance (Ψ) is set by the location where boundary shear stress applied by expanding, radially averaged flow falls below the threshold of sediment motion. The model predicts that the distance to the first island scales with water discharge, scales inversely with flow depth, and scales with the inverse square root of median grain diameter. Finally, from experiment to field scales, distances to island locations are predicted within a factor of two.},
doi = {10.1002/2017jf004464},
journal = {Journal of Geophysical Research. Earth Surface},
number = 2,
volume = 123,
place = {United States},
year = {2018},
month = {2}
}
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