Recent changes in channel morphology of a highly engineered alluvial river – the Lower Mississippi River

Joshi, Sanjeev; Jun, Xu

doi:10.1080/02723646.2017.1340027

Cited by 13 publications

(20 citation statements)

References 36 publications

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“…This paper focuses on the lowermost reach of the LMR (Figure 1), extending from the ORCS juncture to the Head of Passes (HOP), which extends from river kilometer (RK) 490 to 0. In general, this study serves as an important extension/comparison to both studies of Joshi and Jun [34], as well as Wang and Xu (see details in Section 1.2). We believe this study will further contribute to understanding of thalweg geomorphology response to a series of engineering interventions in the LMR region over a relatively long-term period (decadal scale).…”

Section: Study Aimsmentioning

confidence: 99%

“…Contrasting these other studies, Joshi and Jun [34] analyzed the riverbed adjustment by using 18 cross-sections near gauging stations, as well as river stage data, from 1992-2013. They found the channel degradation was only observed in a 60-km reach (out of 500 km in total), whereas all the other reaches were either experiencing gradual aggradation, or showed no significant change over time.…”

Section: Study Sitementioning

confidence: 99%

“…Furthermore, Wang and Xu [14] utilized the hydrographic survey data from 1992-2013 and identified both degrading and aggrading sub-reaches; nevertheless, this study also indicated that a vast amount of sediment was deposited in the LMR channel, especially between RK 386 and 163. Note that one important aim of this study is to extend and compare the study period from Wang and Xu [14] and Joshi and Jun [34]. As both these studies merely focused on the period from the 1980s to the 2010s, our study covers from the 1950s to present.…”

Section: Study Sitementioning

confidence: 99%

“…These sounding points were spaced at 30-40-m intervals along each cross-section. With sufficient spatial and temporal resolution, several previous studies utilized these datasets for their research [6,14,19,22,34,37,69,77,78]. In our study, these hydrographic transects were employed to construct the thalweg profiles for six different times, including 1952, 1963, 1975, 1992, 2004, and 2013.…”

Section: Constructing Thalweg Profilesmentioning

confidence: 99%

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Decadal-Scale Variations of Thalweg Morphology and Riffle–Pool Sequences in Response to Flow Regulation in the Lowermost Mississippi River

Mossa

2019

Water

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The lowermost Mississippi River (LMR) is one of the largest deltaic systems in North America and one of the heavily human-manipulated fluvial river systems. Historic hydrographic surveys from the mid-1900s to the early 2010s were used to document the thalweg morphology adjustments, as well as the riffle-pool sequences. Extensive aggradation was observed during 1950s to 1960s, as the Atchafalaya River was enlarging before the completion of the Old River Control Structure (ORCS). Following the completion of the ORCS, reductions in sediment input to the LMR resulted in net degradation of the thalweg profile patterns since the mid-1960s except for the 1992-2004 period. Different flood events that supplied sediment might be the cause of upstream aggradation from 1963-1975 and net aggradation along the entire reach from 1992-2004. Furthermore, the change pattern of thalweg profiles appear to be controlled by backwater effects, as well as the Bonnet Carré spillway opening. Results from riffle-pool sequences reveal that the averaging W s ratios (length to channel width) are 6-7, similar to numerous previous studies. Temporal variations of the same riffles and pools reveal that aggradation and degradation might be heavily controlled by similar factors to the thalweg variations (i.e., sediment supply, backwater effects). In sum, this study examines decadal-scale geomorphic responses in a low-lying large river system subject to different human interventions, as well as natural flood events. Future management strategies of this and similar river systems should consider recent riverbed changes in dredging, sediment management, and river engineering.

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Section: Study Aimsmentioning

confidence: 99%

Section: Study Sitementioning

confidence: 99%

Section: Study Sitementioning

confidence: 99%

Section: Constructing Thalweg Profilesmentioning

confidence: 99%

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Decadal-Scale Variations of Thalweg Morphology and Riffle–Pool Sequences in Response to Flow Regulation in the Lowermost Mississippi River

Mossa

2019

Water

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“…Both USACE and USGS did not have daily discharge records for St Francisville. However, the Q d s at Tarbert Landing were used for daily sediment and sand load estimations at St Francisville because the river discharge is approximately same for corresponding river stages at Tarbert Landing and St Francisville [36]. River discharge measurements were used for suspended load analysis specifically and both river stage and discharge measurements were used for bedload analysis.…”

Section: River Stage Discharge and Bathymetric Datamentioning

confidence: 99%

Bedload and Suspended Load Transport in the 140-km Reach Downstream of the Mississippi River Avulsion to the Atchafalaya River

Joshi

2017

Water

Self Cite

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The Mississippi River Delta has been continuously losing land since the 1930s due to several factors, chief of which is the reduced sediment supply. A few recent studies have estimated individual components of short-term sediment transport, i.e., bedload and suspended load, separately for some locations along the Lowermost Mississippi River (LmMR, commonly considered as the last 500-km reach of the Mississippi River before entering the Gulf of Mexico). However, the combined effects of both components on the long-term sediment supply along the river reach are still unclear. One of the major obstacles here hindering our understanding is that it is difficult and impractical to accurately measure bedloads in large alluvial rivers, such as the Mississippi. In this study, we estimated bedloads of three medium grain sizes (D 50 = 0.125, 0.25 and 0.5 mm) for three locations along the uppermost 140-km reach of the LmMR: Tarbert Landing (TBL) at river kilometer (rk) 493, St Francisville (St F) at rk 419, and Baton Rouge (BTR) at rk 367.5 during 2004-2015. We also estimated suspended loads at St F during 1978 and at BTR during 2004 in order to discern the interactive relationship between bedloads and suspended loads. We found gradually increasing bedloads for all the three medium grain sizes from TBL (83, 41.5 and 20.75 million tons (MT), respectively) to BTR (96, 48 and 24 MT). We also found that suspended loads at TBL (reported previously) were significantly higher than those at St F and BTR during corresponding overlapping periods. Bedloads increased almost linearly with suspended loads, river discharge and river stage at the upstream locations (TBL and St F); however, such a relationship was not evident downstream at BTR. The total sediment load (bedload + suspended sediment load) was substantially higher at TBL (931 MT), while lower and nearly equal at other two downstream locations (550 MT at St F and 544 MT at BTR) during 2004-2010 (the matching period of availability of both loads). These findings indicate that the uppermost 20-25 km LmMR reach (covering TBL) has potentially entrapped substantial suspended load over the last three to four decades, while bedload transport prevails in the lower reach (covering St F and BTR). We suggest that future sediment management in the river should seek engineering solutions for moving trapped coarse sediments downstream towards the coast for the Mississippi River Delta restoration.

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Estimate of decadal‐scale riverbed deformation and bed‐load sediment transport during flood events in the lowermost Mississippi River

Mossa

Jaeger

2022

Earth Surf Processes Landf

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Riverbed changes are important to applications in engineering in the environment, such as navigation, salt‐water intrusion and habitat quality. This study employed decadal hydrographic data over the past 50 years (1963–2013), as well as daily water stages and discharges to outline the long‐term channel morphological changes and bed‐load sediments deposited by floods in the lowermost Mississippi River (LMR). To generate accurate bathymetric digital elevation models (DEMs), we interpolated the hydrographic survey in a channel‐centred coordinate system by employing ordinary kriging with anisotropy. Riverbed deformations were estimated by subtracting the elevations between DEMs at two different times to generate a series of DoDs (DEM of difference). The results from DoDs exhibit temporal riverbed change patterns and also reveal net degradation after the completion of the Old River Control Structure in 1963, except for the period 1992–2004. Spatially, over 32% of the total area experienced continuous erosion, with only 0.4% having continuous aggradation. Historical erosion over the past 50 years could be removing the alluvial veneer in sections of the river, and exposing more non‐alluvial sediments, particularly between river kilometre RK 230 and RK 40. Our analysis also shows that riverbed deformation patterns are mainly controlled by flood events, backwater effects, as well as the drawdown effect near the Bonnet Carré spillway. In this study, we also examine whether the LMR traps bed‐load sediment under flood conditions. The probability distribution estimated by Monte Carlo simulation suggests only low amounts of bed‐load sediments are deposited on the channel bed during floods. Spatially, the short‐term bed‐load erosion/deposition pattern roughly matches the decadal‐scale riverbed deformation estimated from DoDs. Moreover, this study finds that the trends between the thalweg changes and riverbed deformation are similar, suggesting that both of these patterns are controlled by the same factors.

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Recent changes in channel morphology of a highly engineered alluvial river – the Lower Mississippi River

Cited by 13 publications

References 36 publications

Decadal-Scale Variations of Thalweg Morphology and Riffle–Pool Sequences in Response to Flow Regulation in the Lowermost Mississippi River

Decadal-Scale Variations of Thalweg Morphology and Riffle–Pool Sequences in Response to Flow Regulation in the Lowermost Mississippi River

Bedload and Suspended Load Transport in the 140-km Reach Downstream of the Mississippi River Avulsion to the Atchafalaya River

Estimate of decadal‐scale riverbed deformation and bed‐load sediment transport during flood events in the lowermost Mississippi River

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