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Morphodynamics of River Deltas in Response to Different Basin Water Depths: An Experimental Examination of the Grade Index Model
Author(s) -
Wang Junhui,
Muto Tetsuji,
Urata Kento,
Sato Toshihiko,
Naruse Hajime
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl082483
Subject(s) - beach morphodynamics , progradation , delta , geology , aggradation , hydrology (agriculture) , structural basin , geomorphology , sediment , sediment transport , oceanography , facies , fluvial , geotechnical engineering , aerospace engineering , engineering
Basin water depth ( h ) governs the long‐term morphodynamics of river deltas, which are embodied in the grade index ( G index ). The G index , a volume‐in‐unit‐time ratio of subaerial sediment allocation to the entire supplied sediment, can be given as a function of the dimensionless basin water depth ( h * ). Tank experiments reported herein reveal that delta progradation and deltaplain aggradation are suppressed and distributary channel migration and avulsion take place less frequently when the G index value is lower (i.e., when the basin water is deeper; h * ≫ 1). If the G index ~0 (i.e., extremely deep basin water; h * ~+∞), the delta can neither prograde nor aggrade, and the distributary channels tend to stabilize. The grade index model helps explain the contrasting morphodynamics of the Liwu Delta (east Taiwan) and Yellow River Delta, as natural examples of deepwater and shallow‐water deltas, respectively.