Long-Term Cumulative Effects of Intra-Annual Variability of Unsteady River Discharge on the Progradation of Delta Lobes: A Modeling Perspective

Weilun Gao, Dongdong Shao, Zheng Bing Wang, William Nardin, Prateek Rajput, Wei Yang, Tao Sun, Baoshan Cui

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)
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Abstract

Rivers, regardless of their scales and geographic locations, are characterized with natural and human-induced variability in their discharges. While previous studies have established the effects of both interannual and intra-annual variabilities of unsteady river discharge on delta morphological evolution, the long-term cumulative effects of intra-annual unsteadiness on the progradation of delta lobes has remained hitherto elusive. To address this issue, numerical experiments using simplified unsteady discharges were performed in Delft3D and compared with those assuming constant bank-full discharges. A modified box model was further used to explore the effects of varying intra-annual unsteadiness on the progradation of delta lobes at reduced computational cost. While the overall trends of the progradation and the ultimate area created were found to be similar between the unsteady discharge scenarios and their corresponding constant bank-full discharge scenarios, the nuances of intermittent zig-zag variation in natural delta lobe area were well reproduced by model simulations assuming unsteady river discharges. In addition, long-term predictions suggested the potential existence of a tipping point in the area growth trajectory beyond which the delta lobe area declines during periods of low discharge. When confounding factors such as waves and variable sediment capture ratio were further taken into consideration, simulation results for unsteady river discharge scenarios exhibit significant deviations from constant bank-full discharge scenarios. The implications of the modeling results for delta protection and restoration measures, such as the water-sediment regulation scheme in the Yellow River and artificial channel diversions in the Mississippi River Delta, are also discussed.
Original languageEnglish
Pages (from-to)960-973
Number of pages14
JournalJournal of Geophysical Research: Earth Surface
Volume124
Issue number4
DOIs
Publication statusPublished - 2019

Bibliographical note

Accepted Author Manuscript

Keywords

  • delta progradation
  • delta restoration
  • numerical modeling
  • unsteady river discharge

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