scholarly journals Autogenic translation and counter point bar deposition in meandering rivers

2021 ◽  
Author(s):  
Z. Sylvester ◽  
P.R. Durkin ◽  
S.M. Hubbard ◽  
D. Mohrig
Keyword(s):  
Satellite Imagery ◽  
Riparian Vegetation ◽  
Kinematic Model ◽  
Time Lapse ◽  
Sediment Deposition ◽  
Lateral Migration ◽  
Meandering Rivers ◽  
Point Bar ◽  
Point Bars ◽  
Meander Bends

Although it has long been recognized that deposition along meandering rivers is not restricted to convex banks (i.e., point bars), the consensus is that sediment deposition on concave banks of channel bends mostly occurs when meander bends translate downstream because erosion-resistant barriers inhibit their lateral migration. Using a kinematic model of channel meandering and time lapse satellite imagery from the Mamoré River in Bolivia, we show that downstream translation and associated concave bank deposition are essential, autogenic parts of the meandering process, and resulting counter point bars are expected to be present whenever perturbations such as bend cutoffs and channel reoccupations create short bends with high curvatures. The implication is that zones of concave bank deposition with lower topography, finer-grained sediment, slack water, and riparian vegetation that differs from point bars are more common than previously considered.

scholarly journals Supplemental Material: Autogenic translation and counter point bar deposition in meandering rivers

2021 ◽  
Author(s):  
Z. Sylvester ◽  
et al.
Keyword(s):  
Meandering Rivers ◽  
Point Bar ◽  
Forward Models ◽  
Point Bars

Animations illustrating the evolution of counter point bars in the study area and in forward models.

The case of the braided river that meandered: Bar assemblages as a mechanism for meandering along the pervasively braided Missouri River, USA

2020 ◽  
Author(s):  
John M. Holbrook ◽  
Sarah D. Allen
Keyword(s):  
Missouri River ◽  
Braided River ◽  
Stream Power ◽  
Meandering Rivers ◽  
Meandering River ◽  
Braided Rivers ◽  
Single Thread ◽  
Point Bars ◽  
Meander Bends ◽  
Exclusive Processes

This paper offers a mechanism for meandering in an otherwise braided river and then discusses its general implications for river processes and fluvial deposits. Braided rivers manage to meander without the paired point bars and single-thread channels that are instrumental in developing bends in other meandering rivers. The driving processes for meandering in these braided systems remain enigmatic. The unchannelized and prechannelized Missouri River is an example of a braided meandering river, and it provides an opportunity to gain insight into these processes. This study utilized historical maps, sequential air photos, and surficial geologic maps both to define the processes by which this braided river meanders, and to characterize the deposits produced by these processes. These data show that the Missouri River meanders by building point assemblages instead of point bars. Repeated accretion of midchannel and lateral bars to a common point on the bank forces development of a meander bend around a point assemblage comprising multiple amalgamated compound bars. This differs from single-thread systems, which expand and translate bends around a single compound point bar. Alternating development of point assemblages forces meandering over successions of meander bends. Braided meander loops grow by expansion and translation like single-thread rivers, but they also may contract to produce counterpoint assemblages. Contraction appears to be the more common means of loop abandonment compared to loop cutoff for the braided Missouri River. This differs from single-thread meandering rivers, where contraction is limited, and loop cutoff is consistently the dominant abandonment process. Deposits of the braided meandering Missouri River differ from deposits of single-thread rivers in the rarity of both meander scrolls and single-thread channel fills. Instead, point and counterpoint assemblages comprise fusiform bar elements bound by small filled remnants of anabranch channels. These assemblages are commonly bound by meander cutbank scars. Cutbank scars associated with contraction, however, tend to be composite rather than discrete erosional surfaces, and they do not tend to bind river-scale abandoned channel fills. The braided meandering Missouri River also differs from wandering rivers because wandering rivers meander by building compound bars instead of assemblages, are more gravelly, have less pervasive and much less mobile midchannel bars, and appear to reflect a transitional intermediate pattern instead of a stable hybrid pattern. Braiding and meandering both expend stream power, and both are mechanisms for achieving channel equilibrium. The Missouri River exhibits both of these processes in tandem; thus, meandering and braiding are not mutually exclusive processes. Braided meandering rivers like the Missouri River are less common than either straight-braided or single-thread-meandering rivers, but they are not unique. The long-held distinction of braided versus meandering patterns for rivers thus may be practical but is not definitive.

scholarly journals Supplemental Material: Autogenic translation and counter point bar deposition in meandering rivers

2021 ◽  
Author(s):  
Z. Sylvester ◽  
et al.
Keyword(s):  
Meandering Rivers ◽  
Point Bar ◽  
Forward Models ◽  
Point Bars

Animations illustrating the evolution of counter point bars in the study area and in forward models.

Upstream and downstream morphodynamic influence in simulated and real meandering rivers

2021 ◽  
Author(s):  
Hossein amini ◽  
Guido Zolezzi ◽  
Federico Monegaglia ◽  
Emanuele Olivetti ◽  
Marco Tubino
Keyword(s):  
Migration Rate ◽  
Machine Learning Techniques ◽  
Stochastic Gradient Descent ◽  
Support Vector ◽  
Lateral Migration ◽  
Remotely Sensed Data ◽  
Meandering Rivers ◽  
Meandering River ◽  
Migration Rates ◽  
Meander Migration

<p>This study investigates the dependency of meander lateral migration rates on the spatial distribution of channel centerline curvature in both synthetic and real meandering rivers. It employs Machine Learning techniques (hereafter ML) to relate observed local lateral meander migration rates with the local and the upstream/downstream values of the centerline curvature. To achieve this goal, it was primarily essential to identify the feasibility of using ML in the meandering river's morphodynamics. We then determined the ability of ML to predict the excess near bank velocity based a set of input data using different regression techniques (linear and polynomial, Stochastic Gradient Descent, Multi-Layer Perceptron, and Support Vector Machine). We then moved forward to study the upstream-downstream influence on local migration rate. Synthetic meandering river planforms, as obtained through the planform evolution model of Bogoni et al. (2017), which is based on Zolezzi and Seminara (2001) meander flow model, were used as test cases for the calibration and check of the different adopted ML algorithms. The calibrated algorithms were then applied to multi-temporal information on meander planform dynamics obtained through the PyRiS software (Monegaglia et al., 2018), to quantify to which extent the upstream and downstream distribution of meander centerline curvature affects the local meander migration rate in real rivers.</p><p>References </p><p>1- Zolezzi, G., & Seminara, G. (2001b). Downstream and upstream influence in river meandering. Part 1. General theory and application overdeepening. Journal of Fluid Mechanics, 438(September 2015), 183–211. https://doi.org/10.1017/S002211200100427X</p><p>2- Monegaglia, F., Zolezzi, G., Güneralp, I., Henshaw, A. J., & Tubino, M. (2018). Automated extraction of meandering river morphodynamics from multitemporal remotely sensed data. In Environmental Modelling & Software (Vol. 105, pp. 171–186). https://doi.org/10.1016/j.envsoft.2018.03.028</p><p>3- Bogoni, M., Putti, M., & Lanzoni, S. (2017). Modeling meander morphodynamics over self-formed heterogeneous floodplains. In Water Resources Research (Vol. 53, Issue 6, pp. 5137–5157). https://doi.org/10.1002/2017wr020726</p><p>4- Benozzo, D.,  Olivetti, E., Avesani, P. (2017). Supervised Estimation of Granger-Based Causality between Time series. In Frontiers in Neuroinformatics. </p><p>https://doi.org/10.3389/fninf.2017.00068 </p><p>5- Sharma A., Kiciman, E. (2020). DoWhy: An End-to-End library for Causal Inference. arXiv preprint arXiv:2011.04216. </p><p>https://arxiv.org/abs/2011.04216</p>

Similar curvature-to-width ratios for channels and channel belts: Implications for paleo-hydraulics of fluvial ridges on Mars

Geology ◽  
2021 ◽  
Author(s):  
Alistair T. Hayden ◽  
Michael P. Lamb ◽  
Alexander J. Carney
Keyword(s):  
Coarse Grained ◽  
Scaling Relations ◽  
Radius Of Curvature ◽  
Finite Width ◽  
Lateral Migration ◽  
River Channels ◽  
Meandering Rivers ◽  
Channel Belt ◽  
Stacking Patterns ◽  
Geometric Consequence

The surface of Mars contains abundant sinuous ridges that appear similar to river channels in planform, but they stand as topographic highs. Ridges have similar curvature-to-width ratios as terrestrial meandering rivers, which has been used to support the hypothesis that ridges are inverted channels that directly reflect channel geometry. Anomalously wide ridges, in turn, have been interpreted as evidence for larger rivers on Mars compared to Earth. However, an alternate hypothesis is that ridges are exhumed channel-belt deposits—a larger zone of relatively coarse-grained deposits formed from channel lateral migration and aggradation. Here, we measured landform wavelength, radius of curvature, and width to compare terrestrial channels, terrestrial channel belts, and martian ridges. We found that all three landforms follow similar scaling relations, in which ratios of radius of curvature to width range from 1.7 to 7.3, and wavelength-to-width ratios range from 5.8 to 13. We interpret this similarity to be a geometric consequence of a sinuous curved line of finite width. Combined with observations of ridge-stacking patterns, our results suggest that wide ridges on Mars could indicate fluvial channel belts that formed over significant time rather than anomalously large rivers.

scholarly journals Influence of Different Satellite Imagery on the Analysis of Riparian Leaf Density in a Mountain Stream

2020 ◽  
Vol 12 (20) ◽  
pp. 3376 ◽  
Author(s):  
Giovanni Romano ◽  
Giovanni Francesco Ricci ◽  
Francesco Gentile
Keyword(s):  
Winter Wheat ◽  
Satellite Imagery ◽  
Vegetation Cover ◽  
Riparian Vegetation ◽  
Deciduous Forests ◽  
Sensor Data ◽  
Mountain Stream ◽  
Landsat 8 ◽  
Area Index ◽  
Sentinel 2

In recent decades, technological advancements in sensors have generated increasing interest in remote sensing data for the study of vegetation features. Image pixel resolution can affect data analysis and results. This study evaluated the potential of three satellite images of differing resolution (Landsat 8, 30 m; Sentinel-2, 10 m; and Pleiades 1A, 2 m) in assessing the Leaf Area Index (LAI) of riparian vegetation in two Mediterranean streams, and in both a winter wheat field and a deciduous forest used to compare the accuracy of the results. In this study, three different retrieval methods—the Caraux-Garson, the Lambert-Beer, and the Campbell and Norman equations—are used to estimate LAI from the Normalized Difference Vegetation Index (NDVI). To validate sensor data, LAI values were measured in the field using the LAI 2200 Plant Canopy Analyzer. The statistical indices showed a better performance for Pleiades 1A and Landsat 8 images, the former particularly in sites characterized by high canopy closure, such as deciduous forests, or in areas with stable riparian vegetation, the latter where stable reaches of riparian vegetation cover are almost absent or very homogenous, as in winter wheat fields. Sentinel-2 images provided more accurate results in terms of the range of LAI values. Considering the different types of satellite imagery, the Lambert-Beer equation generally performed best in estimating LAI from the NDVI, especially in areas that are geomorphologically stable or have a denser vegetation cover, such as deciduous forests.

Small-scale experiments on ice-jam initiation in a curved channel

1994 ◽  
Vol 21 (5) ◽  
pp. 719-727 ◽  
Author(s):  
Gilberto E. Urroz ◽  
Robert Ettema
Keyword(s):  
Froude Number ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Small Scale ◽  
Curved Channel ◽  
Point Bar ◽  
Ice Jams ◽  
Ice Jam ◽  
Point Bars ◽  
River Bends

Two principal ice-jam initiation mechanisms, namely, lodgement and gorging, were identified through ice conveyance experiments in a small-scale, curved flume of rectangular cross section. Polyethylene blocks and beads were used to simulate ice fragments. Lodgement occurred for ice fragments that were large relative to channel width, while gorging took place when ice pieces were relatively small and were transported through the channel in multilayer. Channel roughness was found to have a significant effect in helping the arching mechanism that produces lodging. Maximum ice-floe concentration before jamming was found to increase linearly with Froude number, F, when gorging was dominant, but showed little dependence on F for ice jams initiated by lodging. Experiments conducted with point bars placed at the bends indicated that ice jams were initiated mainly by beaching of floes on the point bar. Maximum ice-floe concentration also increased linearly with Froude number for the point-bar experiments. Key words: ice-covered rivers, river bends.

Determining lateral migration rates of meandering rivers using fallout radionuclides

Geomorphology ◽  
2010 ◽  
Vol 123 (3-4) ◽  
pp. 364-369 ◽  
Author(s):  
E. Black ◽  
C.E. Renshaw ◽  
F.J. Magilligan ◽  
J.M. Kaste ◽  
W.B. Dade ◽  
...  
Keyword(s):  
Lateral Migration ◽  
Meandering Rivers ◽  
Migration Rates ◽  
Fallout Radionuclides
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