• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.466-466
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• 2012

하천의 하구에서는 해수의 흐름에 따른 연안토사의 이동과 하천유황에 따른 상류에서의 토사량에 따라 하상이 변화한다. 특히 하구부에서의 퇴적토사 증가는 하천의 수질변화와 어도단절 등으로 인해 하천환경에 악영향을 끼칠 수 있는 하구폐쇄를 발생시킬 수 있어 이에 따른 모니터링이 필요하다. 본 연구에서는 동해안으로 유출되는 지방 1급 하천인 가곡천과 호산천을 대상으로 하구부 퇴적토사의 변화를 모니터링 하였다. 하상변화의 모니터링은 최신장비인 지상 LiDAR를 이용하여 다시기로 스캔한 지상 LiDAR 측정자료를 활용하여 퇴적량을 산출하고 퇴적과 침식의 변화양상을 분석하였다. 분석결과 퇴적지점과 침식지점 및 이에 대한 체적량 변화를 정밀하게 확인할 수 있었다. 지상 LiDAR를 활용한 하상변화 분석기법은 정밀한 퇴적량 추이를 빠르게 관찰할 수 있어 하구지역 뿐만 아니라 하천 전반에서의 하상변화를 조사하는 데에 있어 활용도가 높을 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.329-329
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• 2015

하천의 지류와 본류가 만나는 합류부 구간은 본류와 지류에서 유입되는 유량의 크기가 달라 복잡한 흐름을 형성하게 된다. 합류부 구간의 흐름특성 변화는 합류부 하상 및 하안의 지형학적 변화에 영향을 미칠 수 있으며 이러한 국부적인 구간에서 발생하는 하상변동 및 하안침식은 급격한 하도의 평면적 변화를 야기할 수 있다. 하상변동과 하안침식은 독립적으로 발생하는 것이 아니라 하도침식과 퇴적 그리고 하안침식과 퇴적이 상호작용하여 하천의 지형학적 변화를 야기한다. 따라서 합류부 구간의 하도 안정성을 확보하기 위해서는 합류부 구간에서 발생하는 하상변동과 하안침식을 연계한 정량적 분석이 필요하다. 본 연구에서는 하안침식과 하상변동이 상호작용하여 하천의 지형학적 변화를 야기할 것으로 예상되는 합류부 구간에 대해 2차원 수치모형인 CCHE2D를 활용하여 하안침식을 연계한 하상변동 분석을 수행하고자 한다. 대상구간은 4대강 살리기 사업 후 합류부 지점에서의 하상침식이 지류 하천 상류 방향으로 전이되는 두부침식 현상이 발생한 지점으로 하상유지공 유실 및 하안침식 문제가 발생하고 있는 남한강과 금당천 합류부 구간이다. 흐름 모의 조건은 4대강 살리기 사업 후 해당구간에서 발생한 가장 큰 홍수 사상인 2013년에 발생한 유량조건을 본류에서 유입되는 유입 유량으로 선정하였으며, 유량-유사량 관계식은 합류부 구간에서 약 9.3 km 떨어진 청미천 원부교 지점의 관계식을 사용하였다. 또한 유사이송공식은 CCHE2D 모형에서 선택 가능한 공식들 중 대상 하천에서 측정한 유사량과 가장 근사한 값을 제시하는 Wu et al.(2000) 공식으로 선택하였으며, 유사이송형태는 총유사량 조건을 적용하였다. 본 연구를 통해 하천과 지류하천이 만나는 합류부 지점에서의 하안침식에 의한 영향을 분석하고 평면적 지형변화를 실제 현상과 유사하게 재현한 수치모의 결과는 하도안정화 대책 수립에 적극 활용할 수 있을 것이다.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.199-199
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• 2022

선행 연구들을 통해 미세지형이 유역에서의 유사 유출량에 영향을 끼침을 알 수 있다. 그러나 여전히 유사-유출에 대한 미세지형의 영향이 불분명하여 유역 내 토양 침식 과정에서 미세지형적 거칠기를 고려할 때 혼란이 야기될 수 있다. 따라서, 유사유출량과 토양침식량에 대한 보다 정확한 예측 및 산정을 위해 미세지형이 토양 침식에 미치는 영향을 명확하게 하는 것이 필요하다. 본 연구에서는 Hairsine-Rose 침식 모형과 동역학파(Dynamic wave) 모형을 사용하여 강우-유출에 따른 미세지형의 유사-유출 과정을 수치적으로 모의하였다. 모의 결과에 따르면, 미세지형은 동일 강우 및 유출 조건에서도 유역 내 유사 유출량을 변화시켰다. 또한, 본 연구의 모의조건 하에서 지반이 비교적 미세토사로 구성된 경우 미세지형이 거칠수록 침식률이 증가하는 반면 지반의 토사가 대부분 굵은 입경을 가질 때는 매끄러운 지형보다 거친 미세지형에서 토양 침식률이 감소함을 확인하였다. 따라서, 지형의 미세지형 변동 정도와 토양침식률 사이에 비례 또는 반비례 관계가 형성됨을 보이고, 이러한 관계를 형성하는 과정에 입경 분포가 미치는 영향을 제시하였다. 마지막으로, 본 연구 결과를 통해 장갑화(armoring) 과정이 입경 분포뿐만 아니라 미세지형의 거칠기에 따라 유역별로 다르게 나타나는 것을 확인하였다. 따라서 유사-유출에 대한 미세지형의 영향을 적절하게 고려하기 위해 부상(Pick-up), 이류 및 퇴적 등 입경 별 퇴적물 이동이 다중 물리적으로 고려되어야 한다는 점을 강조한다. 본 연구를 통해 지표면의 미세지형적 거칠기 및 토양 입경에 대한 정확한 정보가 필요함을 알 수 있으며, 이를 충분히 고려한다면 강우 유출에 의한 토양 침식 메커니즘에 대한 이해도와 토양침식량에 대한 정량적 예측의 정확도가 향상될 것으로 예상된다.

• Journal of The Geomorphological Association of Korea
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• v.18 no.2
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• pp.39-51
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• 2011

In this study, the shape of the Baramarae beach, Anmyeondo Area in West Coast of Korea and the changes in the sedimentation and erosion environment were analyzed in time series. As a result of the time series analysis of the shape of the Baramarae beach using aerial photographs from 1967 to 2009, the sand spit that developed in the southern part of Halmi Island was found to have had an EEN direction, but it was changed to a NNS direction, as reflected in the 2009 aerial photographs, as it gradually shifted to the west. In the onsite measurement, the H-3, H-4, H-5, and H-6 spots showed a superior sedimentation environment and the H-7, H-8, and H-9 spots showed a superior erosion environment. It was thus found that sedimentation is superior in the southwest beach and that erosion is superior in the northeast beach. The results in the spots between H-3 and H-6 indicate that the sand in the beach could not move to the northeast beach of Halmi Island due to the bank that had been established in the southwest beach of the island. On the other hand, it seems that superior erosion takes place in spots H-7 to H-9 in the northeast beach, where sand is not provided from the southwest beach of Halmi Island. It was found from the seasonal analysis that the season when superior sedimentation takes place in all the spots is autumn, and that the season when superior erosion takes place is summer. Superior sedimentation takes place in winter and spring in the southeast side and in summer in the northwest side.

• Journal of the Korean earth science society
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• v.26 no.6
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• pp.584-596
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• 2005

Morphology, surface sediments, sedimentation rates and sea-cliff erosion have been monitored, for one year to investigate the shoreline changes and tidal beach characteristics in Cheonsu Bay along the west coast of Korea. The seacliff of the bay consists of intensively weathered sedimentary rocks and soft soil, showing an erosion range of $-58.9\~73.3cm/yr$ by a weak wave forcing. Active sea-cliff erosions are recognized by peculiar geomorphic features, including saw teeth-shaped coastline, gravels, relict weathered basement-rock and 'Island Stack' exposed on the high-tide beach surface. The beach sediments show low compositional maturity at the south and north headlands and gradually high towards the central part. This observation seems to be caused by the fact that beach sediments are to originate from the both headlands in the study area and then transported by long-shore current associated with a wave action.

• Journal of Korea Water Resources Association
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• v.38 no.4 s.153
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• pp.313-321
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• 2005

The elimination and erosion of cohesive sediments in port and reservoir water can so far be processed only with mechanical evacuation methods under extreme energy expenditure. The so-called flushing jets do not serve the purpose because they cannot set the material spaciously in motion despite high shear stresses at the bed. Therefore this study aims to examine the resuspension of the deposited fine material($Al_{2}O_3$) under presence of gas bubbles in order to decreased cohesive sediments in multipurpose dam, port and lakes. In the case of laboratory trial important parameters considered are supplied amount of air and the consolidation time of the solid materials. With increasing gas content alumina remains in suspension at high pH values in the laboratory test, where the particles fall mote rapidly without air addition.

• 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.

• Journal of Korea Water Resources Association
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• v.45 no.7
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• pp.657-674
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• 2012

This paper presents the effect of spatially-distributed rainfall on both rainfall-sediment-runoff and erosion or deposition in the experimental Cheoncheon catchment: upstream of Yongdam dam basin. The rainfall fields were generated by three rainfall interpolation techniques (Thiessen polygon: TP, Inverse Distance Weighting: IDW, Kriging) based only on ground gauges and two radar rainfall synthetic techniques (Gauge-Radar ratio: GR, Conditional Merging: CM). Each rainfall field was then assessed in terms of spatial feature and quantity and also used for rainfall-sediment-runoff and erosion-deposition simulation due to the spatial difference of rainfall fields. The results showed that all the interpolation methods based on ground gauges provided very similar hydrologic responses in spite of different spatial pattern of erosion and deposition while raw radar and GR rainfall fields led to underestimated and overestimated simulation results, respectively. The CM technique was acceptable to improve the accuracy of raw radar rainfall for hydrologic simulation even though it is more time consuming to generate spatially-distributed rainfall.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.1
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• pp.13-20
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• 2007

This study was performed to provide fundamental data for long-term geomorphic predictions of estuarine sandbars in the Nakdong River. We monitored the geomorphic changes of Jinudo (Jinu Island), which is located on the far-southern side of the first western sandbar. We evaluated the temporal and spatial dynamics of the sandbar and the relationship between erosion and deposit speed with environmental factors. We found that: 1) The south side of Jinudo showed very rapid water channel closing and shoal generation. This phenomenon was more obvious during autumn (September and October) than during spring, with greater water depth reduction and variation between sides. 2) The mean deposit speed for Jinudo was approximately 0.85 mm/day. The deposit speed was 1.32 and 1.26 mm/day for the east and south sides of Jinudo, respectively. The maximum deposit and erosion speeds were 27 mm/day and 26 mm/day in July and December, respectively, on the east side of the island. 3) Mean surface deposit size was 0.18-0.26 mm. The newly deposited sandbar had a rotatively larger deposit size than the original land. 4) Correlation analysis showed that, on the southern side of the island, deposit activity prevailed in the winter due to low precipitation and a northerly wind, while erosion was dominant in the summer due to high water flow and a southerly wind. In contrast, the correlation analysis for the eastern side of the island showed that deposition is dominant when water flow is high. These results indicate that geomorphic dynamics vary among island sides.

• Economic and Environmental Geology
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• v.48 no.4
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• pp.301-312
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• 2015

A commercial gas field was found in the southwestern continental shelf of the Ulleung Basin, East Sea in the late 1990s. To develop additional gas field, an exploration well was drilled through the coarse infill of submarine canyon near the gas field, but it was uneconomic to develop hydrocarbons. Using newly acquired deep seismic reflection and previous well data, we have identified additional geological structure which has hydrocarbon potentials below submarine canyons in the southwestern margin of the basin. Based on the interpretation of the deep seismic reflection and well data, the sequences of the study area can be classified into the syn-rift megasequence(MS1), post-rift megasequence(MS2), syn-compressional megasequence(MS3), and post-compressional megasequence(MS4) in relation to the tectonic events. MS1, deposited simultaneously with the basin formation before the middle Miocene, is characterized by chaotic seismic facies with low- to moderate-amplitude and low frequency reflections. MS2 comprises laterally continuous, low- to moderate-amplitude reflections, showing progradational stacking patterns due to high rates of sediment supply during basin expansion in the middle Miocene. MS3 is mainly composed of continuous reflections with high amplitude and moderate- to high-frequency which are interpreted as coarse-grained sediments. The coarse-grained sediments of MS3 sequence is widely truncated by several submarine canyons which filled with fine-grained sediment of MS4 to form a stratigraphic trap of hydrocarbon. Therefore, the reservoir and seal of the hydrocarbon trap in the study area are coarse-grained sediment of MS3 and submarine canyon filled with fine-grained sediment of MS4, respectively. A flat-spot seismic anomaly, which may indicate the presence of hydrocarbon, is observed within the stratigraphic trap.