scholarly journals NATURAL BAR-BYPASSING OF SAND AT A TIDAL INLET

1982 ◽  
Vol 1 (18) ◽  
pp. 90
Author(s):  
Walter J. Sexton ◽  
Miles O. Hayes
Keyword(s):  
Sediment Accumulation ◽  
Tidal Inlet ◽  
Tidal Channel ◽  
Tidal Prism ◽  
Cross Sectional ◽  
Sediment Volume ◽  
Overall Stability ◽  
Ebb Tidal Delta ◽  
Channel Configuration ◽  
Wave Induced

Captain Sam's Inlet, a shallow unstable inlet, periodically migrates up to three kilometers (km) alongshore over a 30- to 40-year period. As the inlet migrates, sediment accumulates at the seaward terminus of the tidal inlet to form a wave-modified ebb-tidal delta that trends downdrift. Continued sediment accumulation on the tidal-delta shoal and subsequent lengthening of the tidal channel in a downdrift direction results in an unstable channel configuration. The ebb delta is eventually breached on its updrift side, releasing a sediment package for inlet bypassing. The sediment-bypassing process was initiated at Captain Sam's Inlet after the final landfall of Hurricane DAVID in September 1979. Initially, the newly formed updrift hurricane channel scoured 1.1 m, migrated updrift, and became the predominant tidal channel at the inlet with eventual abandonment of the prehurricane, main ebb channel. These two channels outlined a portion of the ebb-tidal delta that was freed for bypassing. The initial sediment volume contained in the bypassing shoal, above the -0.6 m (-2 ft) MSL contour, was 47,000m3. The sediment volume of the bypassing shoal did not change significantly until final attachment to Seabrook Island. This channel dominance and the wave-induced migration of the bypassing sediment package aided the bypassing of sand at the inlet. Immediately after filling of the prehurricane, main ebb channel on the delta, the downdrift beaches began accreting. The accretion continued throughout the bypassing process. The tidal prism and cross-sectional area reflected little change during the bypass, showing evidence of the system's overall stability.

scholarly journals On the Tidal Prism: The Roles of Basin Extension, Bottom Friction and Inlet Cross-Section

2021 ◽  
Vol 9 (1) ◽  
pp. 88
Author(s):  
Marco Petti ◽  
Sara Pascolo ◽  
Silvia Bosa ◽  
Nadia Busetto
Keyword(s):  
Cross Section ◽  
Bottom Friction ◽  
Static Method ◽  
Tidal Prism ◽  
Empirical Relationships ◽  
Cross Sectional ◽  
Asymptotic Regime ◽  
Static Regime ◽  
The One ◽  
Basin Area

The prism of the Lignano tidal inlet was approximately constant over the last forty years, although the section width has halved. This has led to questions concerning the factors that most influence the tidal prism, and on the applicability of the well-known A–P relationship. A conceptual scheme of the sea–channel–lagoon system has been used to perform a sensitivity analysis of different parameters that characterize both the basin and the inlet cross-section. A 2D hydrodynamic model has been applied to evaluate the prism and compare it to the one derived by a static method, which is the basis of the analytical derivation of the A–P linkage. Three regimes have been found in the prism variability as a function of the basin extension: a linear static regime between prism and basin area; an asymptotic regime in which the prism depends only on the basin bottom friction; and an intermediate one. In addition, the roles of the inlet and channel sizes on the prism value have been investigated. The results, compared to the empirical relationships between the prism and the inlet cross-section, show that a variation in the cross-sectional area does not always corresponds to a change in tidal prism.

scholarly journals Comparative Analysis of Different Mobile LiDAR Mapping Systems for Ditch Line Characterization

2021 ◽  
Vol 13 (13) ◽  
pp. 2485
Author(s):  
Yi-Chun Lin ◽  
Raja Manish ◽  
Darcy Bullock ◽  
Ayman Habib
Keyword(s):  
Flow Direction ◽  
Sediment Accumulation ◽  
Digital Terrain Model ◽  
Vertical Direction ◽  
Point Clouds ◽  
Lidar Data ◽  
Cross Sectional ◽  
Premature Failure ◽  
3D Point Clouds ◽  
Mapping Systems

Maintenance of roadside ditches is important to avoid localized flooding and premature failure of pavements. Scheduling effective preventative maintenance requires a reasonably detailed mapping of the ditch profile to identify areas in need of excavation to remove long-term sediment accumulation. This study utilizes high-resolution, high-quality point clouds collected by mobile LiDAR mapping systems (MLMS) for mapping roadside ditches and performing hydrological analyses. The performance of alternative MLMS units, including an unmanned aerial vehicle, an unmanned ground vehicle, a portable backpack system along with its vehicle-mounted version, a medium-grade wheel-based system, and a high-grade wheel-based system, is evaluated. Point clouds from all the MLMS units are in agreement within the ±3 cm range for solid surfaces and ±7 cm range for vegetated areas along the vertical direction. The portable backpack system that could be carried by a surveyor or mounted on a vehicle is found to be the most cost-effective method for mapping roadside ditches, followed by the medium-grade wheel-based system. Furthermore, a framework for ditch line characterization is proposed and tested using datasets acquired by the medium-grade wheel-based and vehicle-mounted portable systems over a state highway. An existing ground-filtering approach—cloth simulation—is modified to handle variations in point density of mobile LiDAR data. Hydrological analyses, including flow direction and flow accumulation, are applied to extract the drainage network from the digital terrain model (DTM). Cross-sectional/longitudinal profiles of the ditch are automatically extracted from the LiDAR data and visualized in 3D point clouds and 2D images. The slope derived from the LiDAR data turned out to be very close to the highway cross slope design standards of 2% on driving lanes, 4% on shoulders, and a 6-by-1 slope for ditch lines.

Bio-geomorphic effects on tidal channel evolution: impact of vegetation establishment and tidal prism change

2012 ◽  
Vol 38 (2) ◽  
pp. 122-132 ◽  
Author(s):  
Wouter Vandenbruwaene ◽  
Tjeerd J. Bouma ◽  
Patrick Meire ◽  
Stijn Temmerman
Keyword(s):  
Tidal Channel ◽  
Tidal Prism ◽  
Channel Evolution ◽  
Vegetation Establishment

Long term monitoring of sewer sediment accumulation and flushing experiments in a man-entry sewer

2006 ◽  
Vol 54 (6-7) ◽  
pp. 109-117 ◽  
Author(s):  
J.-L. Bertrand-Krajewski ◽  
J.-P. Bardin ◽  
C. Gibello
Keyword(s):  
Field Experiments ◽  
Sediment Accumulation ◽  
Clear Correlation ◽  
Sediment Removal ◽  
Sediment Volume ◽  
Sediment Mass ◽  
Physical And Chemical ◽  
Parameter Values ◽  
Continuous Field

This paper presents continuous field experiments carried out during 4 years in a man-entry egg-shaped combined sewer in Lyon, France in order to contribute to the knowledge and the modelling of sediment accumulation and sediment removal by means of a Hydrass flushing gate. The 250 μm sediments are mainly mineral, and their physical and chemical characteristics appear as rather stable in time and space. Long-term sediment monitoring reveals: i) a regular asymptotic increase of both the sediment mass and the slope of its longitudinal profile, ii) a clear correlation between local sediment profile irregularities and sewer ancillaries but without significant influence on the global and long term accumulation. Simple sediment accumulation modelling shows: i) a good suitability of a three parameters conceptual model to reproduce asymptotic sediment volume accumulation, and ii) a good suitability of the Velikanov model to reproduce sediment profiles. Both models reproduce observations with an acceptable margin of uncertainty for operational management purposes but are very sensitive to input data and parameter values. The Hydrass flushing gate is efficient and it appeared that the mass of sediments moves downstream linearly with the number of flushes.

scholarly journals A SEMI-ANALYTIC MODEL OF TIDAL INLETS AND THEIR EVOLUTION

2018 ◽  
pp. 62
Author(s):  
Magnus Larson ◽  
Almir Nunes ◽  
Hitoshi Tanaka ◽  
Hans Hanson
Keyword(s):  
Water Exchange ◽  
Flow Model ◽  
Transport Model ◽  
Analytic Model ◽  
Sectional Area ◽  
Tidal Prism ◽  
Tidal Inlets ◽  
Cross Sectional ◽  
Inlet Velocity ◽  
Sediment Transport Model

The water exchange between the sea and a lagoon or bay through an inlet due to tides is a classical topic that has been investigated in a large number of studies (Keulegan, 1967; O’Brien and Dean, 1972; O’Brien and Clark, 1974; Escoffier, 1977). In this paper, a simple semi-analytic model of the flow induced by tides through an inlet connecting the sea to a lagoon or bay is developed. The model is employed to derive explicit expressions for key parameters associated with inlet flows such as bay water level amplitude, tidal prism, maximum inlet velocity, and mixing (retention) time. Also, the inlet flow model is combined with a sediment transport model to determine the conditions for equilibrium as well as the evolution of the inlet cross-sectional area towards equilibrium or closure.

scholarly journals REDUCTION PROCESS OF CROSS-SECTIONAL AREA AT RIVER MOUTH

1986 ◽  
Vol 1 (20) ◽  
pp. 113
Author(s):  
Takuzo Shimizu ◽  
Kosuke Kondo ◽  
Ryoichi Kajima
Keyword(s):  
River Mouth ◽  
Reduction Process ◽  
Field Measurements ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Tidal Prism ◽  
Cross Sectional ◽  
Reduction Processes ◽  
The Cross ◽  
Crosssectional Area

Reduction processes of the cross-sectional area at a river mouth were investigated on the basis of numerical simulations and field measurements, in order to predict the possibility of closing of the mouth of the Samegawa River, Fukushima, Japan. As a result, it was found that the decrease in tidal prism, induced by a reduction of the cross-sectional area, had an important effect on the closing of the river mouth. By considering this effect and estimating the sediment transport rate properly, a practical prediction model was successfully established for simulating the reduction processes of the crosssectional area at the river mouth.

scholarly journals Reconciling Spatial and Temporal Patterns of Cenozoic Shortening, Exhumation, and Subsidence in the Southern Bolivian Andes

2021 ◽  
Vol 9 ◽  
Author(s):  
Nicholas D. Perez ◽  
Ryan B. Anderson ◽  
Brian K. Horton ◽  
Bailey A. Ohlson ◽  
Amanda Z. Calle
Keyword(s):  
Sediment Accumulation ◽  
Foreland Basin ◽  
High Elevation ◽  
Thrust Belt ◽  
Spatial And Temporal Patterns ◽  
Eastern Cordillera ◽  
Sediment Volume ◽  
Bolivian Andes ◽  
Climate Shifts ◽  
Flexural Modeling

The Bolivian Andes are an archetypal convergent margin orogen with a paired fold-thrust belt and foreland basin. Existing chronostratigraphic constraints highlight a discrepancy between unroofing of the Eastern Cordillera and Interandean Zone fold-thrust systems since 40 Ma and the onset of rapid sediment accumulation in the Subandean Chaco foreland after 11 Ma, previously attributed to Miocene climate shifts. New results from magnetostratigraphic, backstripping, erosional volumetric calculations, and flexural modeling efforts are integrated with existing structural and thermochronologic datasets to investigate the linkages between shortening, exhumation, and subsidence. Magnetostratigraphic and backstripping results determine tectonic subsidence in the Chaco foreland basin, which informs flexural models that evaluate topographic load and lithospheric parameters. These models show that Chaco foreland subsidence is consistent with a range of loading scenarios. Eroded volumes from the fold-thrust belt were sufficient to fill the Chaco foreland basin, further supporting the linkage between sediment source and sink. Erosional beveling of the Eastern Cordillera, local intermontane sediment accumulation after 30–25 Ma, and regional development of the high-elevation San Juan del Oro geomorphic surface from 25 to 10 Ma suggest that the western Eastern Cordillera did not store the large sediment volume expected from erosion of the fold-thrust belt, which arrived in the Subandean Zone after 11 Ma. Eocene to middle Miocene foreland basin accumulation was likely focused between the Eastern Cordillera and Interandean Zone, and has been almost completely recycled into the modern Subandean foreland basin. The delay between initial fold-thrust belt exhumation (early Cenozoic) and rapid Subandean subsidence (late Cenozoic) highlights the interplay between protracted shortening, underthrusting, and foreland basin recycling. Only with sufficient crustal shortening, accommodated by eastward advance of the fold-thrust belt and attendant underthrusting of Brazilian Shield lithosphere beneath the Subandes, did the Subandean zone enter proximal foreland basin deposystems after ca. 11 Ma. Prior to the late Miocene, the precursor flexural basin was situated westward and not wide enough to incorporate the distal Subandean Zone. These results highlight the interplay between a range of crustal and surface processes linked to tectonics and Miocene climate shifts on the evolution of the southern Bolivian Andes.

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