Wave flume experiments on the formation of longshore bars produced by breaking waves
Coastal dynamics ; Coastal environment ; Experimentation ; Japan ; Model ; Sand bar ; Vortex
Mechanisms and processes of longshore bar formation were investigated in connection with vortices induced by breaking waves in the laboratory. Four kinds of wave-flume experiments were conducted using a two-video-camera system to examine
the vortices and bar formation in detail. Four process models on bar formation are constructed based on the action of vortices: they are models for break-point single bar, inshore single bar, successive multiple bars, and simultaneous multiple bars
. The occurrence condition for these four types of bars can be quantitatively determined.
The central aim of this research is to enhance the understanding of the behaviour of alongshore bars in a water depth of about 2 to 7 m on the time scale of years (medium scale). Such bars are a frequent morphological phenomenon along the Dutch
coast. To that end, processes on a much smaller time scale were studied; these processes may be responsible for the observed multi-year bar behaviour. The field research was carried out at the central part of the North sea coast at Terschelling
Controls on formation and form of barred nearshore profiles in Thematic Issue II.
Linear regression is used to examine effects of maximum fetch length and nearshore slope in controlling characteristics of barred nearshore profiles. Data came from twelve sites in the Great Lakes and two in the Gulf of St. Lawrence. Fetch length
is a good predictor of height of the outer bar, depth to the crest, and offshore distance| bar number correlates significantly with decreased nearshore slope. Incident waves are the dominant control on nearshore bar formation and maintenance during storms.
Morphodynamics of intertidal bars in wave-dominated coastal settings - a review
Beach ; Coastal dynamics ; Coastal environment ; Earth surface processes ; Intertidal zone ; Sand bar ; Sediment transport ; Tide ; Wave
The aims of this review are to identify the dominant morphodynamic processes governing intertidal bar systems and provide a conceptual framework with which these bars can be further investigated. It is the dominant importance of tidal water level
variations and wave processes in shallow water depths (swash and surf zone bores), rather than wave height variability and deeper water wave processes (breaking and shoaling waves), that constitutes the main difference between intertidal and subtidal bar
Channel bar dynamics on multi-decadal timescales in an active meandering river
Aerial photography ; Bar ; Channel geometry ; Cheshire ; Discharge ; England ; Fluvial dynamics ; Meander ; Photointerpretation ; Riparian vegetation ; Stream ; Typology ; United Kingdom
Four sets of aerial photographs in the period 1984-2007 were used to map and quantify bar numbers and areas in GIS on an active meandering reach of the River Dane (Cheshire). Bar types were classified. Additional temporal resolution was provided
by annual ground photography and mapping for 1981-2010. Analysis was extended backward by use of large scale Ordnance Survey maps from 1873 onwards. As expected, point bars are the most common type but free bars of several types are major components of bar
deposition. Bar activity shows a relation with discharge events and phases and possibly with changing riparian conditions, but superimposed on this is a common sequence of bar evolution from incipient gravel mid-channel bars to full floodplain integration
. This life-cycle is identified as 7-9 years on average. No evidence for mobility of free bars within the course is found. Variability of bar occurrence needs to be taken into account in river management and ecological evaluation.
Formation of stationary alternate bars in a steep channel with mixed-size sediment : a flume experiment
Alternate bars were formed by sediment transport in a flume with Froude-modelled flow and relative roughness characteristic of gravel-boulder channels with steep slopes. This paper describes the experiment and present arguments that steep channel
gradients and widely graded sediment enhance the stability of alternate bars.
Through investigating 11 profiles of the bar, two types of vertical depositional sections are recognized, one dominated by large trough cross-bedding and the other by opposite inclined bedding. The point bar is divided into six sub-facies according
Hydrodynamics, sediment transport, and daily morphological development of a bar-beach system
Coastal dynamics ; Coastal environment ; Coastal geomorphology ; Hydrodynamics ; Intertidal zone ; Netherlands (The) ; Sand bar ; Sediment transport
The aim of this research is the increase of the knowledge of the behaviour of nearshore breaker bars on the short to medium time scale (days to weeks) and to reveal the hydrodynamic and sediment transport processes underlying this behaviour
. The research focuses on processes associated with the transformation and breaking of high-frequency wind-waves near the inner of the two nearshore breaker bars of Egmond aan Zee (Central Dutch Coast). - (AGD)
Configuration of channel bars in Černá Opava River as a consequence of flooding in September 2007
The article deals with changes of setting of channel bars which originate from the overbank flooding events. Channel bars carry information about a flow behavior during and out of flooding. They characterize processes inside the river channel
. Channel bars got connected with the banks due to their enlargement after the flood. - (EN)
Coastal dynamics ; Coastal environment ; Denmark ; Intertidal zone ; Sand bar ; Sediment transport ; Storm ; Suspended load
This paper examines the processes responsible for the morphodynamics of an intertidal swash bar at Skallingen, Denmark, during 7 successive storms. The contributions of gravity waves, infragravity waves and mean currents to the cross-shore suspended
sediment transport are systematically described and related to the morphological response of the intertidal swash bars at Skallingen.
Coastal environment ; Coastal geomorphology ; Earth surface processes ; Nearshore zone ; Netherlands (The) ; Remote sensing ; Sand bar ; Years 1990-99
The central objective of this thesis was to improve the understanding of nearshore bar behaviour over time scales ranging from days to years, using a 3,4-year data set of ARGUS video images (from March 1995 to September 1998) of the double barred
Characteristics and dynamics of multiple intertidal bars, north Lincolnshire, England
The objectives of this paper are : to examine the geographic distribution of multiple intertidal bars along the coastline of England and Wales to indicate the environmental conditions (geomorphologic setting, waves, tides) that characterize
such morphology; to describe the longshore and cross-shore variability of intertidal bar geometry; and to gain insight into inter- and intra-annual intertidal bar dynamics.
Morphological changes on meander point bars associated with flow structure at different discharges
Bar ; Channel geometry ; Discharge ; Finland ; Geophysics ; Hydrogeomorphology ; Meander ; Stream ; Stream flow
This study investigates the impact of flow structure of different discharges on meander point bar morphology. The study reach is located in northern Finland on the meandering, unregulated Pulmanki River in the valley of Pulmanki. The AA. carried out
mobile and terrestrial laser scanning campaigns before and after a flood on 2 sandy-bed point bars. Between the scans, the flow structure was examined using an Acoustic Doppler Current Profiler at 3 flow stages. The results indicated that a meander point
bar both affects and in turn, is itself modified by the flow at different discharges. The lower flow stages also have a significant effect on point bar morphology, especially on deposition over the bar head. Secondary circulation is responsible
for scroll bar formation on the point bar margin beyond the apex. Finally, the shape of the bend and the grain size distribution control the impacts of the flow structure, leading to divergent morphologies of point bars with certain generic features.
River mouth bar formation, riverbed aggradation and channel migration in the modern Huanghe (Yellow) River delta, China
This paper addresses the recent (1970s-1990s) processes of river mouth bar formation riverbed aggradation and distributary migration in the Huanghe River mouth area, in the light of station-based monitoring, field measurements and remote sensing
interpretation. The results show that the morphological changes of the river mouth bar have been closely associated with the largely reduced fluvial discharge and sediment load. Landform development such as bar progradation occurred in 2 phases, before and after
1989, which correspond to faster and lower bar growth rates, respectively. Furthermore, the history of river mouth bar formation reflects human impacts.
Short-term intertidal bar mobility on a ridge-and-runnel beach, Merlimont, northern France
Coastal dynamics ; Coastal environment ; Coastal sedimentation ; Digital elevation model ; Earth surface processes ; France ; Intertidal zone ; Longshore current ; Nord-Pas-de-Calais ; Sand bar ; Sediment transport ; Topography
Digital elevation models and topography profiles of a beach with intertidal bar and through (ridge-and-runnel) morphology in Merlimont, near Somme estuary, were analysed in order to assess patterns of cross-shore and longshore intertidal bar
mobility. The beach exhibited a pronounced dual bar-trough system that showed cross-shore stationarity. The bars and throughs were, however, characterized by significant longshore advection of sand under the influence of suspension by waves and transport
Six experimentally derived formulae that predict the conditions for alternate bar formation and equilibrium bar dimensions are assessed using field data. The study site is an artificially straightened section of the Embarras River located 16 km
south of Champaign, Illinois. Data were collected on channel form, gradient, alternate bar dimensions, bar sediment size, and flow conditions over a two-year study period.
A field test of Tubino's (1991) model of alternate bar formation
This study investigates the fluvial dynamics of straight natural stream channels. In particular, this experimental field study quantitatively assesses a physically based non-linear mathematical theory of alternate bar formation under unsteady
natural flow conditions within a straight alluvial stream. The study site is an artificially straightened section of the Embarras River located approximately 16 km south of Champaign, Illinois. Data were collected on channel form, gradient, alternate bar
This article presents a biogeographic analysis of vegetation on point bars. The results are based primarily on an analysis of off-road mapping, which was conducted in nine selected point bars of the upper stream of the Sava River. Human interference
and functional significance of point bars have been researched, too. As a result of our research a graphic model of succession on the point bars has been created. - (L'A.).
Mid-channel bar growth and its relationship to local flow strength and direction
This paper provides data on the spatial and temporal pattern of surface velocity as mid-channel bar growth is initiated downstream of a fixed junction scour in a generic scale flume model. These flume data and interpretations are compared
to descriptions in the literature of the braiding process. A new model for mid-channel bar growth is presented which helps explain the long-term development of the confluence-diffluence unit.