• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.2
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• pp.54-63
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• 2010

The intensive rainfall over 455 mm occurred between on 9 to 14 July 2009 triggered debris flows around the mountain area in Jecheon County. We mapped the debris flow area and estimated the debris flow volume using a high resolution digital elevation model (DEM) generated respectively from terrestrial LiDAR (Light Detection And Ranging) and topographic maps. For the LiDAR measurement, the terrestrial laser scanning system RIEGL LMS-Z390i which is equipped with GPS system and high-resolution digital camera were used. After the clipping and filtering, the point data generated by LiDAR scanning were overlapped with digital map and produced DEM after debris flow. The comparison between digital map and LiDAR scanning result showed the erosion and deposition volumes of about $17,586m^3$ and $7,520m^3$, respectively. The LiDAR data allowed comprehensive investigation of the morphological features present along the sliding surface and in the deposit areas.

• Journal of Ocean Engineering and Technology
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• v.28 no.3
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• pp.236-244
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• 2014

This study considered a seagrass habitat in order to analyze the characteristics of a marine environment of seagrass located in the Seomjin river estuary, through an analysis of the distribution of the water depth, field observation, and three-dimensional numerical experiments using an EFDC model. The seagrass habitat was usually distributed at D.L(-) 0.5~0.0 m, and was hardly seen in the intertidal zone higher than that range. The distribution of the water temperature was within the range of $7.0{\sim}23.2^{\circ}C$, and the seagrass was demonstrated to have a strong tolerance to changes in the water temperature. In addition, the salinity distribution was found to be 27.2~31.0 psu, with suspended solids of 32.1 mg/L, which were higher than the previous research results (Huh et al., 1998), implying that there may be a reduction in the amount of deposits caused by the suspended solids. As for the sedimentary facies, they were comprised of 62.7% sand, 19.1% silt, and 18.2% clay, indicating that the arenaceous was superior and the sedimentary facies were similar to that of Dadae Bay. According to a numerical experiment, the maximum tidal current was 75 cm/s, while the tidal residual current was 10 cm/s, confirming that it sufficiently adapted to strong tidal currents. The erosion and deposition are predicted to be less than 1.0 cm/year. Thus, it is judged that the resuspension of sediments due to tidal currents and the changes in sedimentary facies are insignificant.

• Journal of the Korean Association of Geographic Information Studies
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• v.23 no.2
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• pp.95-105
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• 2020

In order to promote efficient coastal management, it is important to continuously monitor the characteristics of the terrain, which are changed by various factors. In this study, time series UAV images were taken of Gyeokpo beach. And the standard deviation of ±11cm(X), ±10cm(Y), and ±15cm(Z) was obtained as a result of comparing with the VRS measurement performance for UAV position accuracy evaluation. Therefore, it was confirmed that the tolerance of the digital map work rule was satisfied. In addition, as a result of monitoring the erosion and sedimentation changes using the DSM(digital surface model) constructed through UAV images, an average of 0.01 m deposition occurred between June 2018 and December 2018, and in December 2018 and June 2019. It was analyzed that 0.03m of erosion occurred. Therefore, 0.02m of erosion occurred between June 2018 and June 2019. From the topographical change analysis results, the area of erosion and sediment height was analyzed, and the area of erosion and sedimentation was widely distributed in the ±0.5m section. If we continuously monitor the topographical changes in the coastal regions by using the 3D terrain modeling results using the time series UAV images presented in this study, we can support the coastal management tasks such as supplement or dredging of sand.

• The Journal of Engineering Geology
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• v.10 no.2
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• pp.52-74
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• 2000

The basement rock of upper stream of Keum River Valley consists of Precambrian gneiss which is resistant to weathering. That of mid and lower stream valley, however, is mainly composed of Mesozoic granites which are vulnerable to weathering. The upstream part of Geum River Basin is typified by the deeply-incised and steep meandering streams, whereas mid and lower part is characterized by wide floodplain and gently dipping river bottom toward the Yellow Sea. In particular flooding deposits, in which are imprinted a number of repetitions of erosion and sedimentation during the Holocene, are widely distributed in the lower stream of Geum River Basin. For understanding of erosions in the mid and lower stream of Geum River Basin, the rate of erosion of each small basins were estimated by using the data of field survey, erosional experiments and GIS ananlysis. It was revealed that erosion rate appeared highest in granite areas, and overall areas, in this field survey were represented by relatively high erosion rates. By implemeatation of remote sensing and imagery data, the temporal changes of river bed sediments for about last 11 years were successfully monitored. Observed as an important phenomenon is that the river bed has been risen since 1994 when an embankment (Dyke) was constructed in the estuarine river mouth. From the results derived from the detailed river bed topographical map made in this investigation, the sedimentation of the lower river basin is considered to be deposited with about 5 cm/year for the last 11 years. Based on this river bed profile analysis by HEC-6 module, it is predicted that Geum River bed of Ganggyeong area is continuously rising up in general until 2004. Although extraction of a large amount of aggregates from Gongju to Ganggyung areas, the Ganggyung lower stream shows the distinct sedimentation. Therefore, it is interpreted that the active erosions of tributary basins Geum drainage basins can affect general river bed rising changes of Geum River.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.69-69
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• 2016

하천은 크게 하도와 홍수터 그리고 제방으로 나눌 수 있으며, 국내에서는 다른 국가들과 다르게 대하천사업 이후 하천의 홍수터에 생태공원이나 체육시설 등과 같은 다양한 친수시설들을 조성하여 활용하고 있다. 하지만 최근 이상기후로 인해 홍수의 발생빈도 및 강도가 증가하고 있으며 여름철 집중호우에 의한 하천의 홍수위 상승은 이러한 친수시설의 침식과 퇴적 등과 같은 침수피해를 가중시키는 원인이 되기도 한다(Ku et al., 2013). 따라서 이와 같은 홍수피해를 예측하기 위해서는 홍수터를 포함한 복단면에서의 수치해석이 선행되어야 하며, 일반적으로 2차원 수치해석이 바람직한 것으로 제안되고 있다(Sato et al., 1989). 또한 하천에서의 2차원 수치해석 결과를 이용하여 침식과 퇴적에 관한 친수시설 안정성 평가 지수를 산정할 수 있으며, 산정된 지수를 통해 홍수터에서의 홍수피해를 예측할 수 있다. 다른 국가에서는 국내와 다르게 홍수터에 대한 활용이 거의 없기 때문에 홍수에 따른 홍수터에서의 위험도를 평가한 연구는 거의 없는 실정이며, 한국에서도 홍수터에서의 홍수위험도 평가에 대한 연구는 Song et al.(2016)이 다른 국가에서 활용하고 있는 제내지에서의 홍수위험도 평가 지수를 홍수터에 도입하여 실제 태풍에 의한 홍수위험도를 간접적으로 평가한 연구 정도가 대부분이라고 볼 수 있다. 따라서 본 연구에서는 Einstein-Krone 공식(1962)을 이용하여 침식과 퇴적을 동시에 고려할 수 있는 Transient Erosion and Deposition Index(TEDI)와 Steady Erosion and Deposition Index(SEDI)를 개발하였다. 또한 개발된 지수를 실제 자연하천에 적용하여 태풍 사상에서의 산정된 지수를 통해 홍수터 안정성을 평가하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.35-35
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• 2023

The main reason for its instability is sediment scouring downstream of hydraulic structures. Both physical and numerical models have been used to investigate the influence of soil properties on scour hole geometry. Nevertheless, no research has been conducted on resistance parameters that affect sedimentation and erosion. In addition, auxiliary structures like wing walls, which are prevalent in many real-world applications, have rarely been studied for their impact on morphology. The hydraulic characteristics of steady flow through a boxed culvert are calibrated using a 3D Computational Fluid Dynamics model compared with experimental data in this study, which shows a good agreement between water depth, velocity, and pressure profiles. Test cases showed that 0.015 m grid cells had the lowest NRMSE and MAE values. It is also possible to quantify sediment scour numerically by testing roughness/d₅₀ ratios (c_s) and diversion walls at a meander flume outlet. According to the findings, c_s = 2.5 indicates a close agreement between numerical and analytical results of maximum scour depth after the culvert; four types of wing walls influence geometrical deformation of the meander flume outlet, resulting in erosion at the concave bank and deposition at the convex bank; two short headwalls are the most appropriate solution for accounting for small changes in morphology. A numerical model can be used to estimate sediment scour at the meander exit channel of hydraulic structures based on the roughness parameter of soil material and headwall type.

• Journal of the Semiconductor & Display Technology
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• v.7 no.1
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• pp.29-34
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• 2008

In this paper, the DE(double erosion) cathode for the reactive magnetron sputtering system is developed for high deposition rate and high target utilization efficiency. The utilization efficiency of the developed DE cathode is 22% higher than that of normal SE(single erosion) cathode. Sputtering process for the nickel oxide thin films with the DE cathode is performed under the following conditions; power with $1kW{\sim}3kW$, pressure with 4mtorr and 8mtorr, oxygen flow ratio with $0%{\sim}80%$. As a result, the hysteresis phenomenon of discharge voltage in 4mtorr is lower than that in 8mtorr and the hysteresis phenomenon of discharge voltage is getting lower as the applied power is getting higher. The structure of cross section and surface roughness of the thin films are observed by FE-SEM and AFM. The structure of cross section of the thin films is columnar and the average surface roughness under oxygen flow ratio of 0%, 52.5% and 65.0% are $2.08{\AA}$, $2.20{\AA}$ and $0.854{\AA}$, respectively.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.2
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• pp.1-11
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• 2018

Probable Maximum Flood (PMF) is mostly applied for the designs of large-scale hydraulic structures and it is estimated by computing the runoff hydrograph where Probable Maximum Precipitation (PMP) is inserted as design rainfall. The existing PMP is estimated by transferring the heavy rainfall from all watersheds of korea to the design watershed, however, in this study, PMP was analyzed by selecting only rainfall events occurred in the design watershed. And then, Catchment-scale Soil Erosion Model (CSEM) was used to estimate the PMF and sediment-runoff yield according to the watershed-based estimated PMP. Although the PMF estimated in this study was lower than the existing estimated PMF in the Yongdam-dam basin, it was estimated to be higher than the 200-year frequency design flood discharge. In addition, sediment-runoff yield was estimated with a 0.05 cm of the maximum erosion and a 0.06 cm of the maximum deposition, and a total sediment-runoff yield of 168,391 tons according to 24-hour PMP duration.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.707-712
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• 2008

Plasma resistant nanocrystalline $Y_2O_3$ films were deposited on alumina substrates through the electron-beam PVD technique. Increasing substrate temperature to $600^{\circ}C$ resulted in the textured microstructures with significantly enhanced adhesion force of the coating to the substrate. During the exposure to fluorine plasma, erosion rate of the coated specimen was higher than that of a sintered yttria specimen, but significantly lower than that of a single crystalline alumina. Considering the adhesion and erosion behaviors observed in the coated specimen prepared at $600^{\circ}C$, the deposition technique appears effective in reducing contamination particles generated from the ceramic parts in the plasma environment.

• Journal of The Geomorphological Association of Korea
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• v.19 no.2
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• pp.161-172
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• 2012

The Taeanhaean National Park is located on the middle of the west coast of Korean peninsula. Due to the relatively high wave energy, large tidal range which is about 7m, and extremely complex coastal line, various coastal land-forms such as mud-flats, sand beaches, sand dunes, sea cliffs etc. are well distributed in this area, and thus various coastal ecosystems are well preserved. However, because of reckless sand diggings and construction of artificial structures in the coastal zone, the natural flowing and exchange of coastal deposits were disturbed and the erosion in the beach and the dune has been seriously accelerated. To understand of the causes of these problems, we tried three times periodical measuring with VRS/RTK GPS instrument at the Hakampo and Anmyeon beach. According to seasonal changes of the coast-line, beach area and cross-section of study sites, generally erosion process was dominated in the summer and deposition process was followed after summer.