• Journal of the Korean earth science society
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• v.24 no.6
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• pp.578-591
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• 2003

To investigate the seasonal variation patterns of tidal flat sediments in semi-enclosed Hampyong and Kwangyang Bays, respectively west and south coasts of Korea, accumulation rate and grain-size in the sediments were monitored during 2${\sim}$4 years. The mud flats in the northern and eastern parts of Hampyong Bay were eroded in summer and deposited in winter, but mixed flats in the southern part of the bay show reversed seasonal variations to the mud flats. These variations are most likely connected with wave actions induced by monsoon and physiographic setting of the tidal flats in the bay. In contrast, the tidal flats of Kwangyang Bay were eroded in summer and deposited in other seasons except summer, different from the case of Hampyong Bay. The physiography of Kwangyang Bay are characterized by dominant flood tides and weak wave actions. However, in summer, the surface sediments were abruptly eroded by occasional typhoons and heavy rainfall. These weather conditions appear to be important factors to accelerate erosion on the tidal flat in semi-enclosed bays, south coast of Korea.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.4
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• pp.287-294
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• 2012

Sedimentary environment in coastal zone has been changing due to a large number of coastal structures and continuous coastal development. As a result, the environment has been changing. In particular, the economic and environmental damage can occur due to cohesive sediment transport closely related with the fate of pollutants. Due to large sea wall construction the ebb dominance in the Mokpo coastal waters has been clearer. Cohesive sediment transport was simulated by the EFDC model. The simulated SS showed good agreements with the observed SS. From the sensitivity analysis of sediment parameters, we found out that the erosion rate, the critical shear stresses for erosion and deposition, and the settling velocity are important factors in cohesive sediment transport modeling.

• Journal of the Korean association of regional geographers
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• v.17 no.4
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• pp.416-431
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• 2011

Hiking trails in Mt Jiri, and Mt Halla, National Park have been examined in terms of their degrading factors. The trails are deteriorated by natural erosion processes as well as human trampling. Trail deterioration is classified into tread lowering, sidewall retreat, path widening and divergence based upon a place where erosional processes occur. Tread lowering and sidewall retreat is generally produced by natural erosion factors, whereas path widening and divergence is generated by human trampling. Rainwash is the most contributing process to tread lowering. By contrast, several processes such as rainwash, needle ice action, deflation, tree falling and animal activity play a major role in sidewall retreat according to physical conditions of a hiking trail. Path widening and divergence could be classified by a factor producing human trampling. There are lots of cases related to rainwash such as the tree root, gravel, and bedrock, exposed by a surface flow lowering a tread and the riser produced by tread scouring. A puddle of rainwater on a flat tread and a fallen tree of Abies koreana in a forest region are also major factors to cause path widening and divergence. A paved tread with stones encourages a hiker to walk out of a trail. Taking a shortcut also results in path widening and divergence without a factor giving a hiker inconvenience on a trail.

• 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.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.331-335
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• 2011

흔히 진흙으로 불리는 점착성 유사는 모래 등의 비점착성 유사와는 다른 특성을 보인다. 가장 큰 특징은 점착력에 의해 서로 엉겨 붙어 큰 덩어리(플럭)를 형성하고 다시 큰 플럭이 파괴되는 과정인 응집현상(Flocculation Process)을 보인다는 것이다. 이 응집현상의 과정을 통해 플럭은 크기 및 밀도를 지속적으로 변화시킨다. 크기 및 밀도의 변화는 플럭의 침강속도를 변화시켜 점착성 유사의 부유, 퇴적, 이송, 확산의 과정에 직접적인 영향을 미친다. 응집현상은 플럭의 침강속도 뿐 아니라 부피농도와 질량농도 사이의 비선형적 관계를 야기하여 흐름 운동량 방정식 유도, 난류의 모형화 등에서도 비점착성 유사와 다른 방향으로 진행된다. 점착성 유사가 우세한 지역의 또 다른 특성은 자기하중에 의한 압밀현상에 따라 발생하는 가변적인 한계소류력이다. 따라서 점착성 유사의 이동을 모형화 하는 과정에서는 가변적인 침식율의 가정 등을 통해 이에 대한 고려가 반드시 이루어져야 한다. 흐름의 운동량 방정식 및 난류 모형에서는 플럭의 부피 농도와 질량농도가 각 항의 물리적 의미에 부합하도록 개별적으로 선택 및 적용되어야 질량보존의 문제 등으로 발생할 수 있는 계산상의 오류를 배제할 수 있다. 적용 결과, 점착성 유사가 우세한 지역에서 나타나는 높은 부유 및 흐름정체기에서의 부유사 존재 등의 특성이 점착성 유사 이동을 위한 모형에서 보다 합리적으로 계산된다는 사실이 확인되었다. 그리고 비점착성 유사에 적합한 이동 모형이 점착성이 우세한 지역에 적용될 경우, 상황에 따라 유사량을 과대 및 과소 산정할 수 있다는 결론이 도출되었다. 조류의 영향이 존재하는 하구부의 경우에는 조류의 형태와 비대칭성에 따라 유사량의 차이가 큰 것으로 나타났다. 조류의 형태는 주로 하구부의 지형에 의해 결정되므로 준설, 매립, 확폭 등과 같은 하구부에서의 사업이 진행되는 경우, 유사량 변화에 대한 고려가 반드시 이루어져야 할 것으로 판단된다.

• Journal of the Korean Geographical Society
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• v.46 no.4
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• pp.425-441
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• 2011

Ridge traversing trail in Mount Jiri National Park is classified as flat, gully-like, unilateral, and asymmetric bilateral, paths based on a location and gradient of paths. These types are interchangeable due to a drainage condition of trail surfaces. Using a rapid survey, the trail is 135.9 cm wide, 23.6 cm deep and $5.1^{\circ}$ in a gradient, respectively. All treads have been compacted due to human trampling. The path width is affected by a slope aspect and a distribution of Sasa borealis. An asymmetric path is wider than a symmetric path. A soil erosion rate is equivalent to $68.9cm^2/year$ for the period from 1960 to 2009, suggesting that the trail has been widened 2.7 cm/year and the tread lowered 0.4 cm/year. Trampling and needle ice action combined with rainwash induced by a pipeflow are dominant erosion processes contributing to the trail expansion.

• Journal of Korea Water Resources Association
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• v.45 no.3
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• pp.291-300
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• 2012

We conducted a three-dimensional numerical simulation by using the FLOW-3D, with RANS as the governing equation, in an effort to track the dam-break wave.immediately after a dam break.in areas surrounding where the dam break took place as well as the bed change caused by the dam-break wave. In particular, we computed the bed change in the movable bed and compared the variation in flood wave induced by the bed change with our analysis results in the fixed bed. The analysis results can be summarized as follows: First, the analysis results on the flood wave in the L-shaped channel and on the flood wave and bed change in the movable-bed channel successfully reproduce the findings of the hydraulic experiment. Second, the concentration of suspended sediment is the highest in the front of the flood wave, and the greatest bed change is observed in the direct downstream of the dam where the water flow changes tremendously. Generated in the upstream of the channel, suspended sediment results in erosion and sedimentation alternately in the downstream region. With the arrival of the flood wave, erosion initially prove predominant in the inner side of the L-shaped bend, but over time, it tends to move gradually toward the outer side of the bend. Third, the flood wave in the L-shaped channel with a movable bed propagates at a slower pace than that in the fixed bed due to the erosion and sedimentation of the bed, leading to a remarkable increase in flood water level.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.2
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• pp.127-135
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• 1999

Grain-size distribution and accumulation rate of surface sediments on the tidal flats in Hampyong Bay, southwestern coast of Korea, were investigated in a sequential interval of 2 months for the period of 27 months (1994. 10~1996. 12). Seasonal variation of grain-size distribution is prevalent on the Shimock tidal flat in the southern side of the innerbay, rather than the Anarc tidal flat in the northern side around the baymouth. This variation, in particular, more distinctive in the areas around the both high and low tide water levels. The Shimock tidal flat shows typical seasonal variation of sedimentary processes, expected under monsoonal climate. Deposition of tine-grained sediments in summer dominates over erosion in winter, resulting in an annual accumulation rate of 3.7 mm/yr. In contrast, sedimentary processes on the Anarc tidal flat is abnormal that have experienced slight deposition of fine-grained sediments in the winter and severe erosion in the summer time, showing a negative annual accumulation rate of -49.6 mm/yr. Erosional processes in this area is interpreted due mainly to change of strength and direction of tidal currents, caused by the artificial construction of dyke for reclamation in the mid-tidal flat. As a result, It is immoderate to conclude whether sedimentary processes of Hampyong Bay is erosional or depositional at current situation. Further studies on sedimentary budget at the entrance to the bay are needed.

• Journal of the Korean Geophysical Society
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• v.2 no.3
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• pp.191-200
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• 1999

Analysis of chirp high-resolution seismic profiles from the central Yellow Sea reveals that depositional environments in this area can be divided into three distinctive zones from west to east: (1) subaqueous delta system near the Shandong Peninsula, (2) erosional zone in the central Yellow Sea, and (3) tidal sand ridges and sand waves near the Korean Peninsula. The Shandong subaqueous delta, extending southward from the Shandong Peninsula, changes gradually into prodelta southeastward. The sediments originated from the Yellow River are transported southward along the Chinese coastal area. The erosional zone in the central Yellow Sea contains numerous paleochannels and shows linear erosional features trending northwest-southeast. The erosional zone would be dominated by non-depositional or erosional processes during the Holocene. Tidal sand ridges and sand waves are well developed along the western coast of Korea. The residual sands, which were originally fluvial sediments at the sea-level lowstand, are interpreted as the result of winnowing process during the sea-level rise. Modern sand ridges generally migrates in a northeast-southwestern direction, which coincide with dominant tidal current direction.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.3
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• pp.149-157
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• 1998

Seasonal changes of topography, sediment grain size and accumulation rate in the Gomso-Bay tidal flat, west coast of Korea, have been studied in order to understand the seasonal accumulation pattern and preservation potential of the tidal-flat sediments. Seasonal levelings across the tidal flat show that the landward movement of both intertidal sand shoals and cheniers accelerates during the winter and typhoon periods, but it almost stops in summer when mud deposition is instead predominant at the middle and upper tidal flats. Seasonal variations of mean grain size were largest on the upper part of middle tidal flat where summer mud layers were eroded during the winter and typhoon periods. Measurements of accumulation depths from sea floor to basal plate reveal that accumulation rates were seasonally controlled according to the elevation of tidal-flat surface. The upper tidal flat where the accumulation rate of summer was generally higher than that of winter was characterized by a continuous deposition throughout the entire year, whereas in the middle tidal flat, sediment accumulations were concentrated in winter relative to summer and were intermittently eroded by typhoons. The lower tidal flat were deposited mostly in winter and eroded during summer typhoons. Can cores taken across the tidal flat reveal that sand-mud interlayers resulting from such seasonal changes of energy regime are preserved only in the upper part of the deposits and generally replaced by storm layers downcore. Based on above results, it is suggested that the storm deposits by winter storms and typhoons would consist of the major part of the Gomso-Bay sediments.