• Journal of the Korean earth science society
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• v.34 no.2
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• pp.120-135
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• 2013

To investigate the changes in depositional environment around Gangneung Harbor, we analyzed the surface sediment textural parameters and topography data collected five times from February 2007 to February 2009. In the study area, sediments were mainly composed of sand and its sediment size became finer at offshore sites. During summer time, however, the sand grains became coarser than winter season near Namhangjin Beach, inside the harbor, and offshore areas. On the other hand, the grain size of Anmok Beach showed a gradual finer trend with time. Compared with the previous studies conducted before the completion of Gangneung Harbor construction, the mean grain size became finer on Anmok Beach, while it was coarser on Namhangjin Beach. The bathymetric changes observed over a 2-year period showed predominant erosion in the area of 5 to 10 m water depths and deposition in 2 to 5 m water depths. The shallower area less than 2 m water depths showed an alternating trend and yet slightly more dominant erosion process. The sediment textural parameters and the distribution of erosion and deposition have changed continuously. Results imply that such changes show long-term trends as well as seasonal variations in which the trend may have been formed after the completion of Gangneung Harbor construction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5D
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• pp.655-662
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• 2009

The monitoring for analyzing coastline variations throughout many years is conducted in this study. Haeundae Beach is selected as a test area. We have collected RTK-GPS survey data, airborne LiDAR survey data from Sept. 2008 to 2005. We've done airborne LiDAR survey 2009 to 2006 and we would analyze coastline changes time series through interactive comparison analysis. The mean coastline distance of Haeundae shore is 1,347m (RTK-GPS) by airborne LiDAR survey (2 times). Coastline distance is decreased approximately 4.5% than mean distance in the November survey of 2008. We know right and left sides of the coastline are eroded and the center section shows us the littoral deposit of 3~7m toward sea. It turns out that the sand both sides is transported to the center section by a wave and tide and we know the coastline distance is getting smaller but the coastline width is getting longer like 2~7m.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.3
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• pp.23-31
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• 2009

The border of the shorelines in a nation is an important factor in determining the border of a national territory, but Korea's shorelines are rapidly changing due to the recent rise in sea level from global warming and growth-centered economic policy over the decades of years. This research was done centering on the areas having well-preserved shorelines as they naturally are and other areas having damaged shorelines in their vicinities due to artificial structures at the two beaches located at the neighboring areas and having mutually homogeneous ocean conditions with each other. First, this research derived the shorelines using the aerial photographies taken from 1947 until 2007 and revised the tidal levels sounding data obtained from a hydrographical survey automation system consisting of Echosounder[Echotrac 3100] and Differential Global Positioning System[Beacon]by using topographical data and ships on land obtained by applying post-processing Kinematic GPS measuring method. In addition, this research evaluated the changes and dimensional variations for the last 60 years by dividing these determined shorelines into 5 sections. As a result, the Haewundae Beach showed a total of 29% decrease rate in dimension as of the year 2007 in comparison with the year 1947 due to a rapid dimensional decline centering on its west areas, while the dimension of the Gwanganri Beach showed an increase in its dimension amounting to a total of 69% due to the decrease in flow velocity by artificial structures built on both ends of the beach-forming accumulation; thus, it was found that there existed a big difference in deposition & accumulation tendency depending on neighboring environment in spite of the homogeneous ocean conditions.

• Journal of Korea Water Resources Association
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• v.56 no.spc1
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• pp.1027-1036
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• 2023

Coastal topographic information is crucial in coastal management, but point measurment based approeaches, which are labor intensive, are generally applied to land and underwater, separately. This study introduces an efficient method enabling land and undetwater surveys using an unmanned aerial vehicle (UAV). This method involves applying two different algorithms to measure the topography on land and water depth, respectively, using UAV imagery and merge them to reconstruct whole coastal digital elevation model. Acquisition of the landside terrain is achieved using the Structure-from-Motion Multi-View Stereo technique with spatial scan imagery. Independently, underwater bathymetry is retrieved by employing a depth inversion technique with a drone-acquired wave field video. After merging the two digital elevation models into a local coordinate, interpolation is performed for areas where terrain measurement is not feasible, ultimately obtaining a continuous nearshore terrain. We applied the proposed survey technique to Jangsa Beach, South Korea, and verified that detailed terrain characteristics, such as berm, can be measured. The proposed UAV-based survey method has significant efficiency in terms of time, cost, and safety compared to existing methods.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.3
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• pp.148-156
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• 2002

The coastline of Hampyung Bay, southwestern coast of Korea, was examined and measured in the field for the understanding of geomorphic changes and sea-cliff erosion processes. The Hampyung-Bay coastline is characterized by steep-face slope and soft soil and/or intensively weathered rock composition. Saw teeth-shaped coastline, and relict weathered basement-rock and "Island Stack" exposed on the beach surface are peculiar geomorphic features indicating active sea-cliff erosion. The coastline in the study area is continuously retreating with the following cyclic process: erosion of cliff base, gravitational landslide or mass wasting, formation of talus, and then erosion and removal of talus. In this study, sea-level rise during summer in the west coast of Korea is suggested as one of the key factors fur the removal of soil taluses and, thereby, accelerating sea-cliff erosion.f erosion.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.1
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• pp.101-115
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• 2006

As coastal erosion is increasing sharply because of sudden changes in the natural environment and increases in artificial development, the problem of coastal erosion become an important issue, socially and economically. To building the data which needed to grasp the situation and find a solution, we need the monitoring system for long-term. In this study, we analyzed the coastal topography and land cover changes in the Haeundae Beach during 60 years. The Haeundae Beach is the most famous beach in the country and coastal erosion are going on. First, we analyzed the change of coastal topography by calculated the coastline and area of the beach using aerial photos during 60 years. We extracted the coastline by digitized on aerial photo and corrected the height of tide level using sounding and GPS survey data. And we computed the area of beach and analyzed the change of area during 60 years. Second, we analyzed the change of land cover using landcover map. We made the detailed landcover map by on-screen digitizing and estimated the soil loss for the area nearby Haeundae Beach. As a result, we could see that the coastline get nearer to land and the area of beach has been reduced in general. We think that interception of sand supply by the development is the artificial cause of coastal erosion. The result of this study would be useful in long-term coastal monitoring and to analyze the cause of coastal environment change. We expect that the result is available on the coastal information system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.552-561
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• 2023

The seafloor topography of Gomso Bay on the west coast of Korea was investigated using subtidal bathymetry and tidal-flat altimetry. Gomso Bay consists of 80% tidal flats and 20% subtidal zone, and is divided into an outer bay and an inner bay by the Jujincheon esturary channel. The outer bay tidal flat, has few tidal channels, has a concave topographic profile, and is characterized by the development of chenier and intertidal sand bars, giving it the appearance of gently sloping, dissipative beaches. The inner bay tidal flat has wide upper and middle tidal flats with a well-developed tidal channel system without cheniers. Moreover, the topographical cross-section between these tidal channels is convex upward, and shows the characteristics of a depositional environment greatly influenced by tidal channels and tidal action. An analysis of the horizontal movement of the tidal flat environment over the past 37 years investigating changes in the iso-depth lines in the Gomso-Bay tidal flat between 1981 and 2018 revealed that the Gomso-Bay tidal flat retreated gradually landward. As a result of analyzing the erosion and sedimentation characteristics of Gomso Bay, assuming that most of the water depth changes were due to changes in the elevation of the sea floor and sea level, an average of 1 cm (0 mm/y) of sediment was eroded in the outer bay over the past 37 years (1981-2018), In the inner bay, an average of 50 cm (14 mm/y) was deposited. Notably, the high tidal flats of the outer bay were largely eroded. Monitoring photographs of the coast showed that most of the erosion of the high tidal flats in the outer bay occurred in a short period around 1999 (probably 1997-2002), and that the erosion resulted from the erosion of sand dunes and high-tide beaches caused by temporarily greatly raised high tide levels and storms.