The geomorphological characteristics of the Mekong River in northern Cambodia: A mixed bedrock–alluvial multi-channel network

Meshkova, Lyubov; Carling, Paul A.

doi:10.1016/j.geomorph.2011.06.041

Cited by 39 publications

(37 citation statements)

References 32 publications

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“…Morphological features found in the Mahakam lakes area are in some respect similar to what was found in Mekong River, especially regarding the embayments [ Darby et al , ]. The Mekong River also features deep pools and limited lateral migration, but these processes can be the consequence of structural constraints [ Meshkova and Carling , ]. Similar to the Strickland River, lateral migration may be limited to the apices of bends, while the largest part of the river is relatively fixed [ Aalto et al , ].…”

Section: Discussionmentioning

confidence: 99%

Sharp bends associated with deep scours in a tropical river: The river Mahakam (East Kalimantan, Indonesia)

et al. 2014

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Autogenic scouring in sharp river bends has received ample attention in laboratory and modeling studies. These studies have significantly advanced our understanding of how flow processes are influenced by strong curvature and how they affect the bathymetry. Here we present a 300 km reach of the Mahakam River in Indonesia, which features several sharp bends (W/R > 0.5), providing a unique field data set to validate existing knowledge on sharp bends. Scour depths were found to strongly exceed what can be expected based on existing understanding of sharp bends and are highly correlated with curvature. A comprehensive stream reconnaissance was carried out to compare the occurrence of sharp bends and deep scours with lateral bank migration. Histograms of the occurrence of erosive, stable, advancing, and bar‐type banks as a function of curvature quantify the switch from a mildly curved bend regime to a sharp bend regime. In mild bends, outer banks erode and inner banks advance. In sharp bends the erosion pattern inverts. Outer banks stabilize or advance, while inner banks erode. In sharply curved river bends, bars occur near the outer banks that become less erosive for higher curvatures. Inner banks become more erosive for higher curvatures but nevertheless accommodate the larger portion of exposed bars. No relation was found between the land cover adjacent to the river and the occurrence of sharp bends. Soil processes may play a crucial role in the formation of sharp bends, which is inferred from iron and manganese concretions observed in the riverbanks, indicating ferric horizons and early stages of the formation of plinthic horizons. Historical topographic maps show the planform activity of the river is low, which may relate to the scour holes slowing down planimetric development.

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Section: Discussionmentioning

confidence: 99%

Sharp bends associated with deep scours in a tropical river: The river Mahakam (East Kalimantan, Indonesia)

et al. 2014

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“…These networks include main channels, secondary channels, and connecting channels. It can be found in many environment types from high latitudes to subtropical and semi-arid (Nanson and Knighton 1996); some examples can be found in San Francisco (Kimmerer 2004), Texas (Phillips 2014), Mekong (Meshkova and Carling 2012), Amazon (Gallo and Vinzon 2005), Guinea, (Capo et al 2009), and China (Hu et al 2011). In some cases, channels can migrate, although they tend to be more stable in a cohesive sediment environment or in the presence of bedrocks and manmade levees.…”

Section: Responsible Editor: Carlos Augusto França Schettinimentioning

confidence: 99%

Suspended sediment dynamics in a tidal channel network under peak river flow

Achete¹,

Wegen²,

Roelvink

et al. 2016

Ocean Dynamics

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Peak river flows transport fine sediment, nutrients, and contaminants that may deposit in the estuary. This study explores the importance of peak river flows on sediment dynamics with special emphasis on channel network configurations. The Sacramento-San Joaquin Delta, which is connected to San Francisco Bay (California, USA), motivates this study and is used as a validation case. Besides data analysis of observations, we applied a calibrated process-based model (D-Flow FM) to explore and analyze high-resolution (∼100 m, ∼1 h) dynamics. Peak river flows supply the vast majority of sediment into the system. Data analysis of six peak flows (between 2012 and 2014) shows that on average, 40 % of the input sediment in the system is trapped and that trapping efficiency depends on timing and magnitude of river flows. The model has 90 % accuracy reproducing these trapping efficiencies. Modeled deposition patterns develop as the result of peak river flows after which, during low river flow conditions, tidal currents are not able to significantly redistribute deposited sediment. Deposition is quite local and mainly takes place at a deep junction. Tidal movement is important for sediment resuspension, but river induced, tide residual currents are responsible for redistributing the sediment towards the river banks and to the bay. We applied the same forcing for four different channel configurations ranging from a full delta network to a schematization of the main river. A higher degree of network schematization leads to higher peak-sediment export downstream to the bay. However, the area of sedimentation is similar for all the configurations because it is mostly driven by geometry and bathymetry.

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“…This reach includes a wide range of channel forms, as reflected in Gupta and Liew (2007) having broken this section of river into four reaches (their reaches 3, 4, 5, and part of 6). For our analysis, the key attribute of all these reaches is bedrock control (and thus we consider it a single reach), though a variety of sedimentary forms are present including sections with alluvial banks and anastomosed channels with rock-core islands covered with a relatively thin veneer of sand and silt (Meshkova and Carling 2012;Van et al 2012). For example, from Sambor to Kratie, the bedrock Figure 2 Reaches of predominantly bedrock vs. alluvial channel, as generalized from Adamson (2001), Gupta (2004), and Carling (2009a).…”

Section: Delineation Of Reachesmentioning

confidence: 99%

Anticipated geomorphic impacts from Mekong basin dam construction

Rubin

Kondolf

Carling

2014

International Journal of River Basin Management

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The Mekong River is undergoing rapid dam construction. Seven mainstem dams are completed or under construction in China and 133 completed or proposed for the Lower Mekong River basin. We combined geomorphic assessments of the Mekong channel and delta with models of sediment trapping by reservoirs to forecast geomorphic change. We expect the biggest changes to occur along alluvial reaches, though stripping of thin sediment deposits in bedrock reaches may also have significant consequences for benthic invertebrates, fishes, and other aquatic organisms dependent on the presence of alluvium in the channel. If all dams are built as proposed, the resulting 96% reduction in sediment supply would have profound consequences on productivity of the river and persistence of the delta landform itself. Strategies to pass sediment past dams should be implemented to reduce the magnitude of sediment starvation and resulting impacts.

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The geomorphological characteristics of the Mekong River in northern Cambodia: A mixed bedrock–alluvial multi-channel network

Cited by 39 publications

References 32 publications

Sharp bends associated with deep scours in a tropical river: The river Mahakam (East Kalimantan, Indonesia)

Sharp bends associated with deep scours in a tropical river: The river Mahakam (East Kalimantan, Indonesia)

Suspended sediment dynamics in a tidal channel network under peak river flow

Anticipated geomorphic impacts from Mekong basin dam construction

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