• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.24 no.5
• /
• pp.366-371
• /
• 2012

High swell has been known for the one of the main causes of beach erosion in the east coast of Korea. In this study, coastal topography changes due to high swells are simulated to find its effect on the backshore by using movable bed experiments and numerical experiments. Sea bottom topographical changes due to various incident waves were investigated using CSHORE model in the numerical experiments. Furthermore, the mechanism and the phenomena of beach erosion due to waves and high swells on the foreshore and backshore were analyzed and compared with movable bed hydraulic experiments.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 2004.08a
• /
• pp.361-363
• /
• 2004

• Journal of Environmental Science International
• /
• v.6 no.6
• /
• pp.589-594
• /
• 1997

A total of 24 surface sediment samples collected from coastal region and fronting of sea cliff on Cape Cod In southeastern Massachusetts, were analyzed to Investigate the sediment transport mechanism. According to the result of grainsize analysis, the overall trend of g.k size decreases from the north(Wood End Beach) to the south(Nauset Light Beachy. The coarser materials tend to be deposited at the foreshore than at the backshore. Especially gavel content(%) Is very high in northern beaches. The lavel fraction tended to concentrate at the toe of the beach. In addition to gravel. the beach and nearshore bar also tended to be deposite of very coarse sand and the Inner fraction accumulate in the offshore bar, Grainsize analyses of sediment Indicates that the coarsest sands Including gravel accumulate In the beach and nearshore bar, the finer fraction winnowed out by wave action to be deposited In the offshore bar. The beach and nearshore bar sands and gavel are subsequently transported laterally by the wave-driven longshore drift, and finally they come to rest in the distal end of Provincetown Hook. The faller offshore sands are trnasported laterally to the south by net southward-directed longshore current.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.8 no.3
• /
• pp.122-133
• /
• 2005

The change of surface sediment composition, shoreline and transection of geography were studied to investigate the Typhoon(Maemi) effect in Naa Beach located in the south area of East sea. In the backshore the volume of gravel is do creased, and increased in the volume of sand. The erosion in the sediment occurred to 4 m in the thickness and effected to 10 m in depth. And the coastline retreated to 12 m after typhoon. During typhoon conditions, higher amplitude waves deepen the wave base, causing much of the lower beach face and the offshore. The upper beach face is extensively eroded during typhoon and sand sediment is redeposited.

• The Korean Journal of Quaternary Research
• /
• v.14 no.1
• /
• pp.1-5
• /
• 2000

During the last three years (1997∼2000), a research project of beach dynamic environmental process and dynamic nature of the Nobong Beach, East Sea of Korea has been carried out for a better understanding of beach cycle (winter and summer). In fact, however, this paper deals with a particular feature of beach dynamics, that is, overwash process of overwash water and its sediments. The overwash mark sediments (OMS) are analyzed to understand various textural characters.

• Journal of the Korean earth science society
• /
• v.39 no.1
• /
• pp.23-45
• /
• 2018

Moderately diverse, but very abundant trace fossils are found from the Late Pleistocene deposits of Jeju Island, Korea. Vertical I-, Y- and U-shaped domichnia of annelids or decapods are, over 2500, extremely abundant, 3D network domichnia of callianassids are, over 200, very abundant, and small sinuous trails of nematode repichnia are, over 50, abundant in number. Horizontal trails attributable to polychaete or worm-like animals are, less than 50, common, but horizontal spreiten burrows, fish traces and crab trackways are, less than 10, rare in occurrence. Of these trace fossils, Taenidium barretti, Undichna britannica and Undichna unisulca represent the first record from the Pleistocene in Asia. Psilonichnus upsilon is the second record in Asia. Crab trackways probably produced by underwater punting gait of sideway walking crabs may represent the first record in the world. In addition, diverse and very abundant footprints of more than 500 hominids, more than 200 birds and more than 1000 mammals are closely associated with these invertebrate trace fossils. Trace fossil assemblage integrated with sedimentary facies is interpreted to have been formed in the marginal marine foreshore to backshore environment corresponding to the Psilonichnus and Skolithos ichnofacies.

• Journal of The Geomorphological Association of Korea
• /
• v.28 no.2
• /
• pp.45-57
• /
• 2021

In this study, the changes in morphology of Dokdo's gravel beach and its responses due to a storm event were analyzed using the aerial photos and 3D LiDAR data obtained during an ecosystem survey of the Dokdo in 2020. Dongdo Island's gravel beach, shown by aerial photo analysis, increased in area due to sedimentation after the construction of a dock, but there was no more significant changes in area after having grown to Sutdolbawi inside the dock. The changes in volume of the gravel beach were indicated based on 3D data acquired in May and November 2020. A strong typhoon that passed in September, 2002, caused erosion on the backshore and sedimentation on the foreshore and formed the berm by about 1.5 to 2 m high. The analysis showed that the sedimentation was 94.76 m³ in volume and 329 m² in area and the erosion was 250.75 m³ in volume and 603m² in area, which suggested that the overall change of the gravel beach was erosion. The changes in the morphology of the gravel beach on Seodo Island occurred with the seasons along with the changes in area. In addition, berms of different altitudes appeared on the southern and northern sides of the spit, which was also estimated to have formed by the seasonal current direction and wave energy.

• Journal of the Korean earth science society
• /
• v.41 no.1
• /
• pp.19-30
• /
• 2020

To understand the impact of typhoons on Gamji gravel beach Taejongdae in Busan, we carried out beach profiling using a VRS-GPS system and a Drone photogrammetry for the typhoons 'Kong-rey' invaded in October 2018 and 'Danas' in July 2019. In addition, grain sizes are analyzed to investigate the overall distribution pattern of gravels on the beach, and the beach topography is surveyed periodically to confirm the recovery rate of the beach. Grain-size analysis reveals that mean gravel sizes, in general, become finer from -6.2Φ to -5.4Φ towards the east in the seashore line direction. Variation in mean sizes is obviously observed in the cross-shore direction. Gravels in the swash zone are relatively fine about -4.5Φ in size and equant in shape, whereas the coarse and oblate gravels ranged from -5Φ to -6Φ are found in the berm. Gamji gravel beach particularly has two lines of berms: a lower berm situated facing beach and an upper berm about 10 m landward. After the typhoon Kong-rey passed by, about 1.4 m of severe erosion in upper berm occurred, and the berm eventually disappeared. On the backshore of the upper berm about 50 cm of erosion took place so that the elevation became lower. However, tangible erosion was not observed in the lower berm. When typhoon Danas hit, rated as mild storm, both upper and lower berm were eroded out. However, about 50 cm of deposition occurred only in the backshore. Only three days later, the new lower berm was formed, meaning that sedimentation rate must be high. This result indicates that Gamji gravel beach is recovered very fast from erosion caused by the typhoons when it is under the fair-weather condition even though beach morphology changes dramatically in a short period of time. Gravel beach is estimated to be or evaluated very resilient to typhoon erosion.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.23 no.6
• /
• pp.710-718
• /
• 2017

After Typhoon Chaba (No.18, 2016) collided with Manseongri Beach, a coastal improvement project was carried out since strong external forces such as waves, storm surges and wave-induced currents were observed to cause beach deformation. The shoreline, beach area and beach volume were periodically surveyed. On the basis of this field data, the beach deformation that occurred at Manseongri Beach has been formally described. Over three months after beach nourishment work began, the beaches were gradually stabilized in terms of natural external forces. However, this stabilization was interrupted by Typhoon Chaba. After two months of typhoon weather, the beach returned to a stable state and no changes were observed until one year after the beach recovery work. Just after the typhoon hit, the shoreline receded from the northern side, where no reduction of external forces occurred, while the rear beach area submerged by breakwater advanced. Also, the beach volume decreased by $3,395m^3$ after the typhoon, due to erosion that occurred on the northern beach, with deposition taking place on the southern backshore area. Therefore, it has been concluded that the coastal improvement project undertaken at Manseongri Beach has significantly contributed to conservation in areas of wave-dominant sediment transport.

• Ocean and Polar Research
• /
• v.43 no.4
• /
• pp.307-320
• /
• 2021

Udo Rhodolith Beach is a small-scale, mixed sand-and-gravel beach embayed on the N-S trending rocky coast of Udo, Jeju Island, South Korea. This study analyzes the short-term topographic changes of the beach during the extreme storm conditions of four typhoons from 2016 to 2020: Chaba (2016), Soulik (2018), Lingling (2019), and Maysak (2020). The analysis uses the topographic data of terrestrial LiDAR scanning and drone photogrammetry, aided by weather and oceanographic datasets of wind, wave, current and tide. The analysis suggests two contrasting features of alongshore topographic change depending on the typhoon pathway, although the intensity and duration of the storm conditions differed in each case. During the Soulik and Lingling events, which moved northward following the western sea of the Jeju Island, the northern part of the beach accreted while the southern part eroded. In contrast, the Chaba and Maysak events passed over the eastern sea of Jeju Island. The central part of the beach was then significantly eroded while sediments accumulated mainly at the northern and southern ends of the beach. Based on the wave and current measurements in the nearshore zone and computer simulations of the wave field, it was inferred that the observed topographic change of the beach after the storm events is related to the directions of the wind-driven current and wave propagation in the nearshore zone. The dominant direction of water movement was southeastward and northeastward when the typhoon pathway lay to the east or west of Jeju Island, respectively. As these enhanced waves and currents approached obliquely to the N-S trending coastline, the beach sediments were reworked and transported southward or northward mainly by longshore currents, which likely acts as a major control mechanism regarding alongshore topographic change with respect to Udo Rhodolith Beach. In contrast to the topographic change, the subaerial volume of the beach overall increased after all storms except for Maysak. The volume increase was attributed to the enhanced transport of onshore sediment under the combined effect of storm-induced long periodic waves and a strong residual component of the near-bottom current. In the Maysak event, the raised sea level during the spring tide probably enhanced the backshore erosion by storm waves, eventually causing sediment loss to the inland area.