scholarly journals Sediment Transport and Morphological Response to Nearshore Nourishment Projects on Wave-Dominated Coasts

2021 ◽  
Vol 9 (11) ◽  
pp. 1182
Author(s):  
Cody L. Johnson ◽  
Brian C. McFall ◽  
Douglas R. Krafft ◽  
Mitchell E. Brown
Keyword(s):  
Sediment Transport ◽  
Numerical Experiments ◽  
Decision Makers ◽  
Construction Technique ◽  
Morphological Response ◽  
Nearshore Processes ◽  
Coastal Modeling ◽  
Shoreline Protection ◽  
Navigation Channel ◽  
Channel Maintenance

Nearshore nourishments are constructed for shoreline protection from waves, to provide sediment nourishment to the beach profile, and to beneficially use dredged sediment from navigation channel maintenance. However, it is poorly understood how placement morphology and depth influence nearshore processes operated on wave-dominated coasts. This study investigates the wave fields, sediment transport, and morphological response to three common nearshore nourishment shapes, nearshore berm (elongated bar), undulated nearshore berm, and small discrete mounds, with numerical experiments utilizing the Coastal Modeling System. The nourishments are placed in depths between 3 m and 7 m with a volume of approximately 100,000 m3 and between 400 m and 1000 m in alongshore length. Numerical experiments are carried out in three distinct coastal settings with representative wave climates and geomorphology. Simulation results indicate that shallower, more continuous berms attenuate the most wave energy, while deeper, more diffuse placements retain more sediment. Results from this study improve the understanding of nearshore nourishment shapes and can support decision makers identifying the most appropriate construction technique for future nearshore nourishment projects.

scholarly journals Effects of proposed navigation channel improvements on sediment transport in Mobile Harbor, Alabama

2018 ◽  
Author(s):  
Davina L. Passeri ◽  
Joseph W. Long ◽  
Robert L. Jenkins ◽  
David M. Thompson
Keyword(s):  
Sediment Transport ◽  
Mobile Harbor ◽  
Navigation Channel

scholarly journals Effects of waves and currents on the siltation problem of Damietta harbour, Nile Delta coast, Egypt

2007 ◽  
Vol 8 (2) ◽  
pp. 33 ◽  
Author(s):  
ABO BAKER.I. ABO ZED
Keyword(s):  
Sediment Transport ◽  
Nile Delta ◽  
Monitoring Program ◽  
Wave Direction ◽  
Littoral Drift ◽  
Wave Refraction ◽  
The North ◽  
Dynamic Factors ◽  
Navigation Channel ◽  
Nile Delta Coast

This study evaluates the effect of prevailing dynamic factors on the sedimentation process in Damietta Harbour along the Nile delta coast of Egypt. The monitoring program spanned the period between 1978 and 1999 and included measurements of waves, currents and bathymetric profiles. The evaluation was based on determination of erosion and accretion rates, current regime, sediment transport, wave characteristics and wave refraction. Results revealed that the predominant wave direction from N-NW sector (86 %) throughout the year is responsible for generation of a longshore eastward current. Less frequent waves from the N-NE sector generate an opposing longshore westward current. The refraction pattern for the prevailing wave direction indicates that the harbour and its navigation channel are located within a divergence of wave orthogonal and in an accretion sediment sink area. The annual net rate of littoral drift on the western side of the harbour is about 1.43 * 105 m3 (accretion), while the annual net rate of littoral drift on the eastern side is about 2.54 * 105 m3 (erosion). Currents fluctuate tremendously in speed and direction, especially during the winter months. Hence, sediment transport takes place in offshore, eastward, and onshore directions. Progressive vector diagrams show that the largest near bottom offshore, onshore and easterly net drift occurs during summer, spring and winter respectively. The onshore sediment transport generated during spring and summer plays an important role in the redistribution of eroded sediments during the winter. The overall study of dynamic factors indicated that the harbour site is characterized by eastern, western, offshore and onshore sediment movements. Therefore, the north-south orientation of the navigation channel, with its depth greater than the surrounding area, interrupts sediment drift from different directions and reduces the current speed. Consequently, the sediments sink within the navigation channel from different directions. The sources of sediments contributing to the siltation process of the harbour and its navigation channels are mainly derived from the Rosetta promontory, Burullus beaches, Damietta promontory and from offshore and the dumping area.

scholarly journals Mechanism of Tsunami-Induced Erosion of Bridge-Abutment Backfill and Its Countermeasures

Water ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 3529
Author(s):  
Tomoaki Nakamura ◽  
Chisato Sugiyama ◽  
Yong-Hwan Cho ◽  
Norimi Mizutani
Keyword(s):  
Numerical Analysis ◽  
Sediment Transport ◽  
Numerical Experiments ◽  
Sediment Suspension ◽  
Downstream Side ◽  
Upstream Side ◽  
Bridge Abutment ◽  
Sediment Transportation ◽  
Bedload Sediment ◽  
The Stability

Tsunamis can destroy bridges in coastal areas. Studies have attempted to unravel the mechanism of tsunami-induced damage and develop effective countermeasures against future tsunamis. However, the mechanisms of tsunami-induced erosion of bridge-abutment backfill and its countermeasures have not been studied adequately. This study investigates this topic using numerical analysis. The results show that the tsunami flowing down along the downstream wing of the abutment induces bedload sediment transport on the ogive section of the backfill on the downstream side of the abutment, resulting in the onset of backfill erosion. Sediment suspension and bedload sediment transportation occur when the backfill inside the abutment starts to flow out from below the downstream wing. This leads to subsidence of the backfill at the upstream side of the downstream wing. The subsequent backfill erosion is mainly caused by bedload sediment transport. Numerical experiments on countermeasures show that extending the wings downward can prevent the acceleration of backfill erosion in the presence of the abutment. A combination of multiple countermeasures, including extended wings, would be more effective in maintaining the stability of the abutment after a tsunami. This suggests the application of such countermeasures to actual bridges as an effective countermeasure against backfill erosion.

scholarly journals NORTH JETTY COASTLINE EVOLUTION AND SHORELINE ENGINEERING, GRAYS HARBOR, WASHINGTON

2018 ◽  
pp. 84
Author(s):  
Aaron Porter ◽  
Vladimir Shepsis ◽  
George Kaminsky ◽  
David Michalsen
Keyword(s):  
Sediment Transport ◽  
Sandy Beach ◽  
Transport Processes ◽  
Shoreline Erosion ◽  
Natural Sediment ◽  
Erosion Processes ◽  
The North ◽  
Coastline Evolution ◽  
Navigation Channel ◽  
The City

This study was initiated by the Port of Grays Harbor and the City of Ocean Shores, WA to address ongoing shoreline erosion processes, and sedimentation at the Grays Harbor Federal Navigation Channel. The North Jetty at the entrance to Grays Harbor Estuary, WA was constructed at the beginning of last century (1907) and resulted in major regional changes to the coastline. During the first 40 years post-construction of the jetty, approximately ten miles of sandy beach shoreline, two miles wide north of the jetty, was created by natural sediment transport processes. The accreted land was the base for the creation of the City of Ocean Shores. Since that time the shoreline has been periodically altered by extreme erosion events.

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