scholarly journals Decadal‐Scale Riverbed Deformation and Sand Budget of the Last 500 km of the Mississippi River: Insights Into Natural and River Engineering Effects on a Large Alluvial River

2018 ◽  
Vol 123 (5) ◽  
pp. 874-890 ◽  
Author(s):  
Bo Wang ◽  
Y. Jun Xu
Keyword(s):  
Mississippi River ◽  
River Engineering ◽  
Alluvial River ◽  
Decadal Scale ◽  
Sand Budget

Climatic control of Mississippi River flood hazard amplified by river engineering

Nature ◽  
2018 ◽  
Vol 556 (7699) ◽  
pp. 95-98 ◽  
Author(s):  
Samuel E. Munoz ◽  
Liviu Giosan ◽  
Matthew D. Therrell ◽  
Jonathan W. F. Remo ◽  
Zhixiong Shen ◽  
...  
Keyword(s):  
Mississippi River ◽  
Flood Hazard ◽  
River Engineering ◽  
Climatic Control ◽  
River Flood

The response of the Lower Mississippi River to river engineering

1996 ◽  
Vol 45 (1-4) ◽  
pp. 433-455 ◽  
Author(s):  
Lawson M. Smith ◽  
Brien R. Winkley
Keyword(s):  
Mississippi River ◽  
River Engineering ◽  
Lower Mississippi River

scholarly journals Riverbed Changes of the Uppermost Atchafalaya River, USA—A Case Study of Channel Dynamics in Large Man-Controlled Alluvial River Confluences

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2139
Author(s):  
Bo Wang ◽  
Y. Jun Xu ◽  
Wei Xu ◽  
Heqin Cheng ◽  
Zhongyuan Chen ◽  
...  
Keyword(s):  
Mississippi River ◽  
River Flow ◽  
River Mouth ◽  
Red River ◽  
Atchafalaya River ◽  
Alluvial River ◽  
Drag Forces ◽  
Confluence Zone ◽  
River Confluences

River confluences are important nodes for downstream sediment transport and geomorphological development. Previous studies have established the knowledge that under natural conditions, river confluence zones experience channel scour followed with middle channel bar development. Less care is however given to the intensity of a confluence scour zone under man-controlled conditions, such as discharge regulation and levee confinement. In general, our knowledge about long-term bed evolution downstream of large alluvial river confluences is limited. Here we conducted a study focused on the 69-km uppermost channel of the Atchafalaya River, the largest distributary of the Mississippi River, to test the hypothesis that the channel downstream of two large tributaries sustains longer-term, extensive bed scouring owing to increased discharge in the main channel and, therefore, mid-channel bars in such a confluence zone cannot be built under confined channel conditions. The Atchafalaya River carries the total flow from the Red River and approximately 25% of the Mississippi River flow, traveling southwards 230 km before emptying into the Gulf of Mexico. We utilized long-term records on water surface elevation and discharge during 1935–2016, as well as channel bathymetry survey data during 1998–2006 to determine changes in hydraulic head and morphologic deformation in the confluence zone. The results from this study show that the combined flow from the Red River and Mississippi River into the Atchafalaya River steadily increased to approximately 5848 cubic meters per second (m3 s−1) in the recent decades, and the channel bed of the uppermost Atchafalaya River experienced considerable erosion since the 1930s. At a specific discharge of 8000 ± 100 m3 s−1, the river stage decreased by 5.8, 5.6, and 4.9 m from 1935 to 2016 at (from upstream to downstream) Simmesport, Melville, and Krotz Springs gauging stations, respectively. The average bed elevation reduced by 1.9 m from 1998 to 2006, although its thalweg increased by 0.3 m. Based on the channel bed assessment, a total volume of 6.6 × 107 m3 sediment was eroded from the uppermost 69 km of the Atchafalaya over the 8 years. The findings suggest that confluence zones of large alluvial rivers under controlled flow and confined levee conditions can experience extensive, long-lasting channel erosion. This can be especially progressive if the channel below a confluence is confined by levees, which can increase drag forces and prevent middle channel deposition. Further studies are needed to determine if the eroded sediment from the uppermost Atchafalaya is carried out to the river mouth or is deposited in the lower Atchafalaya. Such knowledge will have both scientific and practical relevance in river engineering and management.

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

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1175 ◽  
Author(s):  
Chia-Yu Wu ◽  
Joann Mossa
Keyword(s):  
Mississippi River ◽  
Management Strategies ◽  
River System ◽  
Temporal Variations ◽  
Large River ◽  
Sediment Supply ◽  
Flood Events ◽  
River Systems ◽  
Decadal Scale ◽  
River Control

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 Ws 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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