The influence of microform bed roughness elements on flow and sediment transport in gravel bedrivers : comment on a paper by Marwan A. Hassan and Ian Reid
The purpose of this discussion is two-fold : 1) to provide a further demonstration of the importance of treating the bedform-flow resistance-sediment transport system in a gravel-bedriver as a dynamic interaction, as has been the case for many
years in the context of sand-bedrivers; and 2) to emphasize the importance of understanding this interaction and the feedback that controls it in terms of the characteristics of near-bed turbulence.
Process-based model of grain lifting from riverbed to estimate suspended-sediment concentration in a small headwater basin
Grain size distribution ; Hokkaido ; Japan ; Meltwater ; Model ; Pic discharge ; Riverbed ; Sand ; Suspended load ; Watershed
Suspended sediment is supplied from riverbed sediment in Hiyamizusawa Brook, Hokkaido, Japan, during the snowmelt season. The stirring up of fine grains from the riverbed is an important control of the time variation of suspended-sediment flux
. A model previously used to explain the stirring up of fine grains within a cobble and pebble bed is applied to a sand bed, with a modification . Consequently, the amount of fine material stirred up from the riverbed is estimated from the grain size
distribution of riverbed sediment, and the suspended flux is thus calculated. The results were equivalent to the field data.
Breakup and reestablishment of the armour layer in a large gravel-bedriver below dams : the lower Ebro
Carrying capacity ; Dam ; Ebro ; Flood ; Grain size distribution ; Hydraulic works ; Riverbed ; Spain ; Stream
This paper describes the breakup and the reestablishment of the bed armour layer in the regulated gravel-bed Ebro River during a flooding period. The study was conducted over a 28-km study reach from 2002 to 2004. The surface, subsurface and bed
load grain size distribution constitute the bases for the analysis of bed-armouring dynamics. The results indicate that the magnitude of floods controlled the degree of armouring of the riverbed. The supply and transport of bed material appear
to be in balance in the river reach immediately below the dam.
A theoretical model of river channel changes is presented, which shows some nonequilibrium thermodynamic criteria of a river channel to bedding and equilibrium.
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-bedrivers are considered. The channel width-bankfull discharge relationship suggested by XU
(1996) for discrimination of channel patterns of sand-bedrivers in China, is also tested in this study by the same database. Discussion of the results.
Australia ; Carrying capacity ; Fluvial processes ; Hydrodynamics ; Methodology ; New South Wales ; Riverbed
The dynamics of riverbeds can be assessed from scour and fill data obtained from scour chains. Chain insertion, anchoring and relocation can be determined with minimal manpower by utilising a set of tested employment methodologies
. These are described in sufficient detail to allow fluvial geomorphologists, ecologists and river engineers to more commonly utilise chains in studies of river stability and river response.
This progress report reviews the research into the processes of : 1) coarse surface layers; 2) armour versus pavement; 3) bed surface structure and sediment transport; 4) imbrication; 5) small- and medium-scale gravel bedforms; 6) gravel bedforms
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-bedrivers. 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.
Underlying gravel layers in a large sand bedriver and their influence on downstream-dam channel adjustment
Bank erosion ; Channel geometry ; China ; Dam ; Fluvial erosion ; Gravel ; Hydraulic works ; Longitudinal section ; Riverbed ; Stream
In this paper, a study is made based on data from the Hanjiang River, the longest tributary of the Yangtze River in China. This example demonstrates the significance of the study of the underlying gravel layers in sand-bedrivers in relation
Measurement of bedload in rivers in Erosion and sediment yield : some methods of measurement and modelling.
Only in recent years have bed load data for rivers existed in sufficient quantity and reliability to facilitate a better understanding of the bedload transport process. Data for the East Fork River, Wyoming indicate that when sand-size particles
are dominant as bedload the bed load accounts for about half the total load. The examples of the Tanana, Snake and Clearwater Rivers indicate that for gravel bedrivers the bed load probably accounts for less than 10 % of the total load.
This paper intends to approach the phenomena of river-bed material variability inside a network of rivers from the drainage basin of Siret as a link between sediment sources and their sediment delivery. The AA. will focus on the spatial variability
of the distribution types of river-bed material and will try to moot the origin of bimodality of river-bed deposits. As opposed to its tributaries, the source of the first mode, of gravel, is allochtonous to the Siret river, generated by the massive input of coarse
Persistence of the surface texture of a gravel-bedriver during a large flood
Channel geometry ; Colorado ; Flood ; Grain size distribution ; Gravel ; Meander ; Meltwater ; Pic discharge ; Riverbed ; Stream ; United States of America
The goal of this paper is to clarify conditions under which the surface layer of a gravel-bedriver may persist during large floods. Detailed field measurements of channel topography and bed surface grain size were made in a gravel-bed reach
of time. During the 2003 peak flow, the river avulsed immediately upstream of the sudy reach. The abandonment was rapid, leaving the bed texture essentially frozen in place.
of the Colorado River prior to a flood in 2003. Runoff produced during the 2003 snowmelt was far above average, resulting in a sustained period of high flow with a peak discharge; all available grain sizes within the study reach were mobilized in this period
Evaluating bed-material transport equations using field measurements in a sandy gravel-bed stream, Arbúcies River, NE Spain
Bed-material load under a wide range of hydraulic conditions was sampled in a poorly sorted, sandy, gravel-bedriver (Arbúcies, NE Spain) during 1991 and 1992. The Arbúcies data showed a marked scatter of bed-material discharges, reflecting the high
variability of bedload rates as well as of suspended concentrations. Bed-material discharges were used to test 5 bedload and bed-material formulae. The degree of agreement between observed and predicted values varies greatly.
This paper presents a detailed assessment of the distributed monitoring and terrain modelling of riverbed topography using a technique that combines rigorous analytical photogrammetry with rapid ground survey. A detailed assessment is undertaken
of the quality of the morphological information acquired. This allow some general comments to be made concerning the use of more traditional methods to monitor and represent small-scale river channel morphology.
A large scale landslide occurred in the Tal valley in late January, 1990. This paper discusses the causes and the mechanism of the riverbed uplift in relation to the landslide along the river bank.
This paper reports on results from a series of experiments conducted in a flume using four types of bed, differentiated by the size of the bed material. These experiments are intended to complement research undertaken into pebble-beddedrivers