The Brahmaputra‐Jamuna River, Bangladesh

Best, James L.; Ashworth, Philip; Sarker, Maminul Haque; Roden, Julie E.

doi:10.1002/9780470723722.ch19

Cited by 91 publications

(85 citation statements)

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“…This confluence angle-scour depth relationship is also supported by laboratory experiment, where scour depth is found to increase systematically at higher junction angles (Best 1988). Data collected on 14 confluence scours in the braided Jamuna River also support these mathematical and laboratory experiments (Flood Action Plan 24 1996a; Best et al 2007). These studies showed that scours produced with confluence angles up to 60u during the flood season are 2-3.5 times the average flow depths of incoming braided threads.…”

Section: Scaling Relationships Of Confluence-scourssupporting

confidence: 59%

“…Nevertheless, there remains disagreement on the scale dependence of confluence scours versus river size (Ashmore and Parker 1983;Best 1988;Best and Ashworth 1997;Sambrook Smith et al 2005). This may reflect the fact that most examples of confluence scours described in the literature are based on small-scale laboratory experiments (Ashmore and Parker 1983;Best 1988) or on scours in modern large braided rivers Ashworth et al 2000;Best et al 2007). Well-documented examples of confluence scours and scour-filling sedimentary facies in ancient outcrops are lacking, in part because there have not been enough studies to establish criteria to identify confluence scours in outcrop.…”

Section: Criteria For Identifying Confluence Scoursmentioning

confidence: 90%

“…Most of the examples of scours described in the sedimentological literature are focused on braided rivers Ashworth et al 2000;Best et al 2007). However, scours in meandering systems are common, as tight river bends can be characterized by a deep thalweg scour in the cut bank.…”

Section: Scours In An Ancient Meandering Systemmentioning

confidence: 99%

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Confluence Scours Versus Incised Valleys: Examples From the Cretaceous Ferron Notom Delta, Southeastern Utah, U.S.A

Ullah¹,

Bhattacharya²,

Dupré³

2015

Journal of Sedimentary Research

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Confluence scours in braided rivers occur where channel threads join together, producing erosional relief that may be considerably deeper than average channel depth. Based on studies of the continental-scale Ganges-Brahmaputra river system, it has been observed that the maximum depth of confluence scours by autocyclic processes may reach up to four to five times the average depth of the incoming channels. Considering the possibility of such massive scours in an ancient fluvial system, it was argued that allogenically produced incised valleys at sequence boundaries should only be properly defined in ancient systems if the erosional relief is more than five times average channel depth.Based on cross-sectional geometries, a number of confluence scour fills were interpreted on well-exposed fluvial outcrops in a Cretaceous-age compound incised-valley system in the Notom delta complex of the Ferron Sandstone Member, Utah. Crosssectional observations from outcrops and comparisons with modern rivers reveal that confluence scours have diagnostic fill facies (single set of large steep foresets) and do not produce multistory sand bodies. A confluence scour fill produces a singlestory body in which a fifth-order scour is filled with unit bar foresets, which in turn are overlain by a fourth-order surface capped by compound bar deposits. The story thickness in the confluence scour does not represent the average channel depth because confluence scours allow preservation of the deepest parts of channels as well as fully preserved abnormally thick stories. Therefore, we argue that interpretation of incised valleys in an ancient system associated with a sequence boundary should not be based on the depth of the erosional surface versus the number of average preserved channel stories. Rather, it should be defined by the erosional relief that is significantly deeper than the thickest fully preserved stories, which in a braided stream are likely to represent confluence scour fills.

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Section: Scaling Relationships Of Confluence-scourssupporting

confidence: 59%

Section: Criteria For Identifying Confluence Scoursmentioning

confidence: 90%

See 1 more Smart Citation

Confluence Scours Versus Incised Valleys: Examples From the Cretaceous Ferron Notom Delta, Southeastern Utah, U.S.A

Ullah¹,

Bhattacharya²,

Dupré³

2015

Journal of Sedimentary Research

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“…This is further illustrated in Fig. 10, which shows the frequency-separated anomalies of river runoff vs. total water storage in the GBD for the flood years of 2004and 2007(Riegger and Tourian, 2014Reager et al, 2015;Sproles et al, 2015). Generally, the hypothesis that storage can drive river runoff tends to indicate a slower process evolution through subsurface water storage and baseflow generation, expressed by a strong correlation at longer (monthly) timescales.…”

Section: The 2007 Floodmentioning

confidence: 93%

“…Two of these major flood events coincide with the GRACE mission's lifetime (March 2002-present). In July 2004, the Brahmaputra exceeded critical flood levels twice in a fortnight, inundating 38 % of the country (Best et al, 2007). In July and September 2007, two separate major flood peaks in the Brahmaputra caused inundation lasting weeks, affecting 42 % of the country (Islam et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Daily GRACE gravity field solutions track major flood events in the Ganges–Brahmaputra Delta

Gouweleeuw

Kvas

Gruber

et al. 2018

Hydrol. Earth Syst. Sci.

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Abstract. Two daily gravity field solutions based on observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission are evaluated against daily river runoff data for major flood events in the GangesBrahmaputra Delta (GBD) in 2004 and 2007. The trends over periods of a few days of the daily GRACE data reflect temporal variations in daily river runoff during major flood events. This is especially true for the larger flood in 2007, which featured two distinct periods of critical flood level exceedance in the Brahmaputra River. This first hydrological evaluation of daily GRACE gravity field solutions based on a Kalman filter approach confirms their potential for gravity-based largescale flood monitoring. This particularly applies to shortlived, high-volume floods, as they occur in the GBD with a 4-5-year return period. The release of daily GRACE gravity field solutions in near-real time may enable flood monitoring for large events.

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Effects of tectonic deformation and sea level on river path selection: Theory and application to the Ganges-Brahmaputra-Meghna River Delta

Reitz

Pickering

Goodbred

et al. 2015

J. Geophys. Res. Earth Surf.

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The set of active rivers of the Ganges-Brahmaputra-Meghna (GBM) Delta in Bangladesh overlies an active plate boundary that continually modifies the landscape of the delta by deformation. The response of rivers to spatially variable subsidence, from tectonic tilting or other causes, has been thought to include preferred occupation of regions of higher subsidence. In this paper, we develop further the theoretical framework for analysis of the interplay of tectonics and river dynamics, and apply this model to conditions in the GBM Delta. First, we examine the overall competition between variable subsidence and channel dynamics, and find that tilting in Bangladesh should be strong enough to influence river path selection. We then present new theory for the effect of subsidence that is spatially (not temporally) variable. We find a constant residence timescale on different parts of the delta, and differing frequencies of avulsion to these locations, and describe the effects of incision or floodplain deposition on these quantities. We present estimates of the channel residence timescale of the Jamuna (Brahmaputra) River reconstructed from the lithology, provenance, and dating of sediment cores. We apply our framework to a map of regional subsidence to predict the effects on avulsion for the Jamuna River. Comparison between our predicted (2150 years) and our stratigraphically based estimates of avulsion timescale (1800 years) shows encouraging consistency.

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The Brahmaputra‐Jamuna River, Bangladesh

Cited by 91 publications

References 0 publications

Confluence Scours Versus Incised Valleys: Examples From the Cretaceous Ferron Notom Delta, Southeastern Utah, U.S.A

Confluence Scours Versus Incised Valleys: Examples From the Cretaceous Ferron Notom Delta, Southeastern Utah, U.S.A

Daily GRACE gravity field solutions track major flood events in the Ganges–Brahmaputra Delta

Effects of tectonic deformation and sea level on river path selection: Theory and application to the Ganges-Brahmaputra-Meghna River Delta

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