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Simulation modelling of river channel erosion in River channel changes.

Simulation modelling of river channel erosion in River channel changes.

Morphology of Red Creek, Wyoming, an arid-region anastomosing channel system

Morphology of Red Creek, Wyoming, an arid-region anastomosing channel system
Aggradation is occuring in the main channel and on the floodplain throughout the study reach. Infilling of the main channel occurs primarily by lateral accretion, while the floodplain accretes vertically through deposition of overbank sediment from
the main channel and anabranches. Infilling of the main channel may cause avulsion of the main channel into an anabranch. The abandoned main channel segment may then fill completely or act as an anabranch. Because lateral migration of channels is inhibited
by the high cohesion of the silt and clay channel sediment, periodic avulsion is the primary form of lateral mobility in the system.

Controls on channel form and channel change in the Bell River, Eastern Cape, South Africa

Controls on channel form and channel change in the Bell River, Eastern Cape, South Africa
Cape Province ; Channel geometry ; Fluvial erosion ; Fluvial hydrology ; Meander ; South Africa ; Stream
Channel instability has occurred in the Bell River in the form of meander cutoffs, incipient meander cutoffs and general channel instability. This is documented for a 40 year period and the causes examined. - (AJC)

A model of channel response in disturbed alluvial channels

A model of channel response in disturbed alluvial channels
The adjustment of channel geometry and phases of channel evolution are characterized by six process-oriented stages of morphologic development : premodified, constructed, degradation, threshold, aggradation, and restabilization. Downcutting and toe
removal during the degradation stage causes bank failure by mass wasking when the critical height and angle of the bank material is exceeded (threshold stage). Channel widening continues through the aggradation stage as the slough line develops
as an initial site of lower-bank stability. Alternate channel bars form during the restabilization stage and represent incipient meandering of the channel.

Channel adjustment and a test of rational regime theory in a proglacial braided stream

Channel adjustment and a test of rational regime theory in a proglacial braided stream
Alberta ; Braided channel ; Canada ; Channel geometry ; Discharge ; Grain size distribution ; Gravel ; Proglacial lake ; Sediment load ; Stream
The AA. analyze the historical trends in channel pattern and the contemporary downstream changes in channel geometry, grain size, and gradient in the gravel bed, proglacial Sunwapta River, Alberta. The rational equations incorporate the effect
of grain size and slope on channel width and the effect of width and grain size on channel slope. The regime equations are successful even though they were devised for single channel gravel streams. The results confirm the influence of grain size on channel
pattern thresholds and demonstrates, using spatial transitions in channel pattern, that channel pattern predictions based on stream power alone are inadequate.

Discrimination of channel patterns for gravel- and sand-bed rivers

Discrimination of channel patterns for gravel- and sand-bed rivers
Braided channel ; Discriminant analysis ; Gravel ; Meander ; River bed ; Runoff ; Sand ; Shear stress ; Stream ; Stream flow
Based on data from around 200 alluvial rivers in several countries, a systematic comparison of flow shear stress and stream power has been made between sand- and gravel-bed rivers. The formation of channel pattern can be regarded as the outcome
of sediment transport and channel bank constraints in an alluvial river. To overcome the difficulty of quantifying channel bank constraints, channel width/depth ratio and a dimensionless channel width index are used to reflect it indirectly.

Types of river channel patterns and their natural controls

Types of river channel patterns and their natural controls
Braided channel ; Channel geometry ; Classification ; Discharge ; Floodplain ; Hydrological regime ; Meander ; Stream ; Terminology
River channel patterns are thought to form a morphological continuum. This continuum is two-dimensional, defined by plan features of which there are three (straight, meandering, branching), and structural levels of fluvial relief of which
there are also three (floodplain, flood channel, low-water channel). Combinations of these three categories define the diversity of patterns. The critical stream power values and hydrological regime together define the channel pattern, and analysis of the pattern

An Experimental study of channel confluences

An Experimental study of channel confluences

River channel changes.

River channel changes.

Link lengths and channel network topology

Link lengths and channel network topology

Channel evolution of the pre-channelized Danube River in Bratislava, Slovakia (1712-1886)

Channel evolution of the pre-channelized Danube River in Bratislava, Slovakia (1712-1886)
Bank erosion ; Bratislava ; Channel geometry ; Danube ; Eighteenth Century ; Flood ; Fluvial dynamics ; Historical mapping ; Human impact ; Meander ; Nineteenth Century ; Slovak Republic ; Stream
Channel adjustments of the Danube River near Bratislava are reconstructed from historical river maps for 1712-1886, the period preceding mid-course channelization. The study reach comprised an anastomosing-meandering planform, characteristic
of the upper area of a large alluvial fan. The key mechanisms of channel change were avulsions through channel switching into chute channels, meander development through progression and cutoffs, and abandonment of secondary channels. The gravel-bed Danube River

Channel pattern discrimination based on the relationship between channel slope and width

Channel pattern discrimination based on the relationship between channel slope and width
Braided channel ; Carrying capacity ; Channel geometry ; Comparative study ; Cross section ; Discriminant analysis ; Fluvial dynamics ; Longitudinal section ; Mathematical model ; Meander ; Model ; River bed ; Roughness ; Slope gradient ; Stream
The classic channel slope-discharge relationship proposed by Leopold and Wolman (1957) for channel pattern discrimination has been tested by a large database including 4 types of rivers : gravel-bed meandering rivers, gravel-bed braided rivers, sand
-bed meandering rivers and sand-bed braided rivers. The result shows that this relationship cannot discriminate channel patterns well when both gravel- and sand-bed rivers are considered. The channel width-bankfull discharge relationship suggested by XU
(1996) for discrimination of channel patterns of sand-bed rivers in China, is also tested in this study by the same database. Discussion of the results.

Catastrophic human-induced change in stream-channel planform and geometry in an agricultural watershed, Illinois, USA

Catastrophic human-induced change in stream-channel planform and geometry in an agricultural watershed, Illinois, USA
Agricultural land use ; Channel geometry ; Drainage network ; Human impact ; Hydraulic works ; Illinois ; Impact ; Rural landscape ; United States of America ; Watershed
This study shows that channelization in the Embarras River basin of east central Illinois has altered stream channel and planform geometrie to an extent that exceeds background rates of change for un channelized reaches by one to two orders
of magnitude. The average rate of change in channel position resulting from stream responses to channelization also greatly exceeds the average rate of change for unchannelized reaches, yet the spatial extent of stream adjustments to channelization is limited
, and most straightened or relocated channels persist in their altered state for decades following channelization.

Some thermodynamic criteria for river channel changes

Some thermodynamic criteria for river channel changes
A theoretical model of river channel changes is presented, which shows some nonequilibrium thermodynamic criteria of a river channel to bedding and equilibrium.

Stream channel pattern : a threshold model

Stream channel pattern : a threshold model
An alternative approach to the analysis of channel pattern is presented. Discussion is focussed on an explanatory model, a logistic regression model, which explicitly represents channel pattern as the dependent variable, and has gradient

Data generation processes for spatial series: the example of ephemeral channel form

Data generation processes for spatial series: the example of ephemeral channel form
Channel ; Gully erosion ; Mass movement ; Methodology ; Model ; Precipitation ; Rill wash ; Time series ; Watershed
Recently developed techniques for time series analysis are applied to channel width and slope series collected in small ephemeral channels in Southern Italy. Tests for the difference between trend and difference stationarity, although developed
in the field econometrics, are found to be more suitable for data generation processes in geomorphology. The ephemeral channel data exhibit trend stationarity and the results of spectral analysis and vector autoregression analysis of detrended channel width

Asynchronous terrace development in degrading braided channels

Asynchronous terrace development in degrading braided channels
This paper describes a process of terrace development in rapidly degrading channels that produces a physically continuous terrace tread that consists of temporally nonsynchronous segments. Moreover, the AA. show that lower terraces developed
in the upstream portion of a degrading channel may correlate with higher terrace surfaces developed farther down channel. The results are based upon data collected and observations made in degrading braided channels in a laboratory flume and in a degrading braided
Channel, Ash Creek, Arizona.

Anastomosis and the continuum of channel pattern

Anastomosis and the continuum of channel pattern
Australia ; Canada ; Channel geometry ; Classification ; Concept ; Flood ; Floodplain ; Fluvial processes ; Meander ; River bed
Anastomosing rivers are characterized by multiple channels separated by islands excised from the floodplain. Their status relative to the continuum concept of channel pattern is assessed with channel pattern defined in terms of three variables: flow
strentgh, bank erodibility and relative sediment supply. Anastomosis may in certain cases represent a transitional form of channel pattern but there is no denying the longevity of some anastomosing systems.

Pool and riffle characteristics in relation to channel gradient

Pool and riffle characteristics in relation to channel gradient
California ; Channel geometry ; Fluvial processes ; Geomorphometry ; Longitudinal section ; United States
The channel gradients, along three rivers in coastal northern California, discussed in this paper are higher than those often reported for channels with pool-riffle, rather sequences. However, the AA. have designated these as pool-riffle, than step
-pool, channels, because of the presence of a strong lateral flow component, and the lack of well-organized bed-steps spanning the entire channel width.

Channel characteristics and formation mechanism of Ganjiang River

Channel characteristics and formation mechanism of Ganjiang River
Bank erosion ; Braided channel ; Channel geometry ; China ; Discharge ; Grain size distribution ; Jiangxi ; Seasonal variability ; Sediment load ; Stream
Relative straight channel of the middle and upper reaches of Ganjiang has been formed due to the contraction of mountains and hills being composed of bedrocks on both banks of the river. But however, at the lower reaches, branching channel
predominates due to limited contracting force of the river banks as the evolution and development of branching channels are closely related with locations and controle effect of nodal points. There are sufficient water containing less sediments in particles

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