Modeling Deltaic Lobe-Building Cycles and Channel Avulsions for the Yellow River Delta, China

Andrew J. Moodie, Jeffrey A. Nittrouer, Hongbo Ma, Brandee N. Carlson, Austin J. Chadwick, Michael P. Lamb, Gary Parker

Research output: Contribution to journalArticle

Abstract

River deltas grow by repeating cycles of lobe development punctuated by channel avulsions, so that over time, lobes amalgamate to produce a composite landform. Existing models have shown that backwater hydrodynamics are important in avulsion dynamics, but the effect of lobe progradation on avulsion frequency and location has yet to be explored. Herein, a quasi-2-D numerical model incorporating channel avulsion and lobe development cycles is developed. The model is validated by the well-constrained case of a prograding lobe on the Yellow River delta, China. It is determined that with lobe progradation, avulsion frequency decreases, and avulsion length increases, relative to conditions where a delta lobe does not prograde. Lobe progradation lowers the channel bed gradient, which results in channel aggradation over the delta topset that is focused farther upstream, shifting the avulsion location upstream. Furthermore, the frequency and location of channel avulsions are sensitive to the threshold in channel bed superelevation that triggers an avulsion. For example, avulsions occur less frequently with a larger superelevation threshold, resulting in greater lobe progradation and avulsions that occur farther upstream. When the delta lobe length prior to avulsion is a moderate fraction of the backwater length (0.3– (Formula presented.)), the interplay between variable water discharge and lobe progradation together set the avulsion location, and a model capturing both processes is necessary to predict avulsion timing and location. While this study is validated by data from the Yellow River delta, the numerical framework is rooted in physical relationships and can therefore be extended to other deltaic systems.

Original languageEnglish (US)
Pages (from-to)2438-2462
Number of pages25
JournalJournal of Geophysical Research: Earth Surface
Volume124
Issue number11
DOIs
StatePublished - Nov 1 2019

Keywords

  • backwater
  • deltaic lobe
  • lowland deltas
  • river avulsion

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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