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Title: 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 » within a factor of two.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]
  1. Univ. of Arkansas, Fayetteville, AR (United States)
  2. Univ. of Wyoming, Laramie, WY (United States); Univ. of Texas, Austin, TX (United States)
  3. 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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