Surface elevation and sedimentation dynamics in the Ganges-Brahmaputra tidal delta plain, Bangladesh: Evidence for mangrove adaptation to human-induced tidal amplification

Bomer, Edwin J.; Wilson, Carol; Hale, R. P.; Hossain, Abu Naser Mohsin; Rahman, Fatema

doi:10.1016/j.catena.2019.104312

Cited by 65 publications

(69 citation statements)

References 80 publications

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“…[78]) and a high degree of physico-chemical stress (e.g., alternating fresh and saline water conditions, [28,29,77]). These interpretations are in accordance with observational studies in the region, documenting sediment accretion rates in excess of 1 cm/yr [79][80][81] and seasonal differences in salinity of~20 psu [41].…”

Section: Progressive Changes In Bedding Typesupporting

confidence: 91%

“…Specifically, we propose that sandy beds are deposited during monsoon conditions, while mud-rich beds are deposited during low flow conditions (i.e., dry season). Centimeter-scale sand beds (e.g., KAL-D, 1.75-1.80 m depth; Figure 7) likely represent sedimentation from a single monsoon flood pulse, as supported by sediment tile accumulation measurements [79,81]. Sand beds on the order of decimeters (e.g., BTP-D, 1.80-2.40 m depth; Figure 7) may indicate the amalgamation of several monsoon flood deposits, a possible product of time periods when repeatedly strong flood pulses eroded fine-grained low-flow deposits (sensu [16]).…”

Section: Progressive Changes In Bedding Typementioning

confidence: 84%

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An Integrated Approach for Constraining Depositional Zones in a Tide-Influenced River: Insights from the Gorai River, Southwest Bangladesh

Bomer

Wilson

Datta

2019

Water

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The tidal to fluvial transition (TFT) of estuaries and coastal rivers is one of the most complex environments on Earth with respect to the transportation and deposition of sediment, owing in large part to competing fluvial and marine processes. While there have been recent advances in the stratigraphic understanding of the TFT, it is still unclear whether these findings are site-specific or representative of mixed tidal-fluvial systems worldwide. Yet, research from this depositional domain holds profound societal and economic importance. For instance, understanding the underlying stratigraphic architecture of channel margins is critical for assessing geomorphic change for fluvio-deltaic settings, which are generally vulnerable to lateral channel migration and resultant erosion. Findings would also benefit paleo-geographic reconstructions of ancient tide-influenced successions and provide an analog for hydrocarbon reservoir models. In the Ganges-Brahmaputra Delta of Bangladesh, the Gorai River is one of two Ganges distributaries actively connected to the Bay of Bengal. With fluvial input from the Ganges and meso-scale (2–4 m range) tides at the coast, the Gorai exhibits a variety of hydrodynamic regimes across its 350-km reach, providing a unique opportunity to investigate along-channel depositional patterns across the TFT. This study integrates multiple datasets—core sedimentology, river channel bathymetry, and remote sensing—to provide a process-based framework for determining the relative position of sedimentary deposits within the tidal-fluvial continuum of the Gorai River. The results of this investigation reveal coincident, abrupt shifts in river channel morphology and sediment character, suggesting the occurrence of backwater-induced mass extraction of relatively coarse sediments (i.e., fine sand). Despite being situated in an energetic tidal environment, evidence of tidal cyclicity in cored sediments is relatively rare, and the bulk stratigraphy appears strongly overprinted by irregularly spaced cm- to dm-scale sediment packages, likely derived from monsoonal flood pulses. Such findings differ from previously-studied mixed tidal-fluvial systems and underscore the site-specific complexities associated with this depositional domain.

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Section: Progressive Changes In Bedding Typesupporting

confidence: 91%

Section: Progressive Changes In Bedding Typementioning

confidence: 84%

An Integrated Approach for Constraining Depositional Zones in a Tide-Influenced River: Insights from the Gorai River, Southwest Bangladesh

Bomer

Wilson

Datta

2019

Water

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“…Values of soil bulk density were then multiplied by % TOC to obtain soil C density. C sequestration rates were calculated as the product of soil C density and average sediment accretion rates derived from long-term 137 Cs activities [51] and short-term sediment tiles [20].…”

Section: Soil Pore-water Content Organic Content and Bulk Densitymentioning

confidence: 99%

“…The combination of tidal inundation and rainfall infiltration raises the groundwater table and saturates the substrate, ultimately causing elevation gain via soil swelling (i.e., "dilation water storage," [55,56]). Conversely, decreased soil pore-water content during the dry season ( Figure 5 or Figure 8A) is caused by evapotranspiration [57] and lowering of the water table [20], contributing to less elevation gain or even elevation loss (Figure 3, Table 1). These trends did not apply to all locations, however, as SSET-6 exhibited substantial elevation gain but minimal changes in seasonal pore-water content ( Figure 5 or Figure 8A).…”

Section: Effects Of Below-ground Process Controls On Surface Elevatiomentioning

confidence: 99%

“…Among the studies that have investigated the surface elevation dynamics and sustainability in mangrove systems, many have focused on changes in the sediment profile extending from the ground surface to the depth of incompressible substrate (e.g., consolidated sand, limestone, volcanic rock), generally occurring between 5 and 15 meters belowground (e.g., [17,18,20,21]). In contrast, comparatively little attention has been given to the uppermost half-meter to meter of the sediment profile, termed the "live root zone" (LRZ), where biological processes have a relatively high influence on surface elevation change [8,22,23].…”

Section: Introductionmentioning

confidence: 99%

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Process Controls of the Live Root Zone and Carbon Sequestration Capacity of the Sundarbans Mangrove Forest, Bangladesh

Bomer¹,

Wilson²,

Elsey‐Quirk³

2020

Sci

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The conservation of coastal wetland ecosystems, like mangrove forests and salt marshes, represents a critical strategy for mitigating atmospheric emissions and climate change in the 21st century. Yet the existence of these environments is threatened by human-induced disturbances, namely deforestation and accelerated sea-level rise. Coastal systems maintain surface elevation in response to sea-level rise through a combination of physical and biological processes both above and below the ground surface. The quantification and relative contribution of belowground process controls (e.g., seasonal water content, organic matter decomposition) on surface elevation change is largely unexplored but crucial for informing coastal ecosystem sustainability. To address this knowledge deficit, we integrated measurements of surface elevation change of the live root zone (0.5 to 1 m depth) with geotechnical data from co-located sediment cores in the Sundarbans mangrove forest (SMF) of southwest Bangladesh. Core data reveal that the primary belowground controls on surface elevation change include seasonal fluctuations in pore-water content and the relative abundance of fine-grained sediments capable of volumetric expansion and contraction. In contrast to many mangrove environments, the soils of the SMF contain little organic matter and are dominantly composed (>90%) of inorganic clastic sediments. The mineral-rich soil texture likely leads to less compaction-induced subsidence as compared to organic-rich substrates and facilitates surface equilibrium in response to sea level rise. Despite a relatively high soil bulk density, soil carbon (C) density of the SMF is very low owing to the dearth of preserved organic content. However, rates of C accumulation are balanced out by locally high accretion rates, rendering the SMF a greater sink of terrestrial C than the worldwide mangrove average. The findings of this study demonstrate that C accumulation in the SMF, and possibly other alluvial mangrove forests, is highly dependent on the continued delivery of sediment to the mangrove platform and associated settings.

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Climate Change

2021

Tropical Marine Ecology

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Surface elevation and sedimentation dynamics in the Ganges-Brahmaputra tidal delta plain, Bangladesh: Evidence for mangrove adaptation to human-induced tidal amplification

Cited by 65 publications

References 80 publications

An Integrated Approach for Constraining Depositional Zones in a Tide-Influenced River: Insights from the Gorai River, Southwest Bangladesh

An Integrated Approach for Constraining Depositional Zones in a Tide-Influenced River: Insights from the Gorai River, Southwest Bangladesh

Process Controls of the Live Root Zone and Carbon Sequestration Capacity of the Sundarbans Mangrove Forest, Bangladesh

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