Observations and scaling of tidal mass transport across the lower Ganges–Brahmaputra delta plain: implications for delta management and sustainability
R. P. Hale,Rachel Bain,Steven L. Goodbred,James L. Best +3 more
- Vol. 7, Iss: 1, pp 231-245
TLDR
In this article, the authors studied the sediment transport in the Sundarbans National Forest and found that sediment transport is flood-oriented, likely as a result of flood-inducing pumping by the main-stem rivers.Abstract:
. The landscape of southwest Bangladesh, a region constructed primarily by
fluvial processes associated with the Ganges River and Brahmaputra River, is now
maintained almost exclusively by tidal processes as the fluvial system has
migrated east and eliminated the most direct fluvial input. In natural areas such
as the Sundarbans National Forest, year-round inundation during spring high
tides delivers sufficient sediment that enables vertical accretion to keep
pace with relative sea-level rise. However, recent human modification of the
landscape in the form of embankment construction has terminated this pathway
of sediment delivery for much of the region, resulting in a startling
elevation imbalance, with inhabited areas often sitting >1 m
below mean high water. Restoring this landscape, or preventing land loss in
the natural system, requires an understanding of how rates of water and
sediment flux vary across timescales ranging from hours to months. In this
study, we combine time series observations of water level, salinity, and
suspended sediment concentration with ship-based measurements of large
tidal-channel hydrodynamics and sediment transport. To capture the greatest
possible range of variability, cross-channel transects designed to encompass
a 12.4 h tidal cycle were performed in both dry and wet seasons during
spring and neap tides. Regional suspended sediment concentration begins to increase in August,
coincident with a decrease in local salinity, indicating the arrival of the
sediment-laden, freshwater plume of the combined Ganges–Brahmaputra–Meghna
rivers. We observe profound seasonality in sediment transport, despite
comparatively modest seasonal variability in the magnitude of water
discharge. These observations emphasize the importance of seasonal sediment
delivery from the main-stem rivers to this remote tidal region. On tidal
timescales, spring tides transport an order of magnitude more sediment than
neap tides in both the wet and dry seasons. In aggregate, sediment transport
is flood oriented, likely as a result of tidal pumping. Finally, we note that
rates of sediment and water discharge in the tidal channels are of the same
scale as the annually averaged values for the Ganges and Brahmaputra rivers.
These observations provide context for examining the relative importance of
fluvial and tidal processes in what has been defined as a quintessentially
tidally influenced delta in the classification scheme of Galloway (1975).
These data also inform critical questions regarding the timing and magnitude
of sediment delivery to the region, which are especially important in
predicting and preparing for responses of the natural system to ongoing
environmental change.read more
Citations
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Journal ArticleDOI
Resilience of River Deltas in the Anthropocene
A.J.F. Hoitink,Jeffrey A. Nittrouer,Paola Passalacqua,John B. Shaw,Eddy J. Langendoen,Y. Huismans,D.S. van Maren +6 more
TL;DR: In the development of reliable tools to design resilient deltas, one of the first challenges is to close the sediment balance at multiple scales, such that morphodynamic model predictions match with fully independent measurements.
Journal ArticleDOI
Surface elevation and sedimentation dynamics in the Ganges-Brahmaputra tidal delta plain, Bangladesh: Evidence for mangrove adaptation to human-induced tidal amplification
TL;DR: In this paper, the authors utilize an array of surface elevation tables, sediment traps, and groundwater piezometers to provide longitudinal trends of sedimentation and elevation dynamics with respect to local platform elevation and associated hydroperiod.
Journal ArticleDOI
Shoreline change assessment using geospatial tools: a study on the Ganges deltaic coast of Bangladesh
TL;DR: The spatiotemporal trend of shoreline position of the Ganges deltaic coast of Bangladesh is revealed and that would be beneficial for the coastal management and planning of the region.
Journal ArticleDOI
Impacts of tidal-channel connectivity on transport asymmetry and sediment exchange with mangrove forests
R. L. McLachlan,Andrea S. Ogston,Nils E. Asp,Aaron T. Fricke,Charles A. Nittrouer,Vando J.C. Gomes +5 more
TL;DR: In this paper, in-situ observations of water and sediment flux were obtained in two tidal channels near the Amazon River to characterize how connectivity impacts sediment transport in coastal mangrove forests.
Journal ArticleDOI
Flow Reorganization in an Anthropogenically Modified Tidal Channel Network: An Example from the Southwestern Ganges‐Brahmaputra‐Meghna Delta
TL;DR: In this article, the authors examined variations in discharge exchange between two parallel, 1-to 2-km wide tidal channels (the Shibsa and the Pussur) in southwestern Bangladesh over spring-neap, and historical timescales.
References
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