• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.20-20
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• 2020

신곡수중보는 한강종합개발사업(1982년~1986년) 중 하도정비로 인하여 상시 수위가 저하됨으로써 조수의 과도한 역류 등으로 발생하는 이수상의 문제점을 해결하고 상류에 설치된 잠실수중 보 사이의 수위유지 및 하천 공간 이용의 극대화, 연안 농경지의 용수공급 및 하천환경 보전을 목적으로 건설되어, 「잠실 및 신곡수중보 관리규정(1986)」 및 「신곡수중보 운영 매뉴얼」에 의해 관리·운영되고 있다. 신곡수중보는 준공된 이래로 한강하류의 흐름 해석에 있어 중요한 기준과 경계로서 이와 관련한 다양한 연구가 진행되었다. 신곡수중보로 인한 흐름의 변화가 하상과 생태에 미치는 영향에 관한 연구와 하구역에서의 조위 및 흐름특성과 밀도류의 거동에 관한 1, 2차원 수치해석연구가 활발히 진행되었다. 본 연구에서는 그동안 1, 2차원 수치해석연구로 한정되었던 신곡수중보 흐름특성에 관련하여 실제 수문 운영 방식을 반영한 3차원 수치해석을 수행하여 구조물의 상·하류에서 발생하는 와류 및 이차류와 같은 3차원적 흐름 구조와 이에 따른 지형의 침식·퇴적 및 구조물에 미치는 영향 등을 구체적으로 분석하였다. 우선, 신곡수중보 운영 매뉴얼과 실제 가동보 운영시스템을 비교하여 수문개방 시기, 유량 기준의 수문 운영 방법, 수위 변화에 따른 수문 운영 방법, 수문개방 순서를 분석하고 신곡수중보 주변 흐름에 대한 3차원 수치해석모형 구축을 위한 경계조건을 산정하였다. 수치해석에는 상용프로그램인 FLOW-3D를 사용하였으며, 경계처리기법 및 난류해석을 위해 FAVOR 기법과 RNG k-ε 모델을 적용하였다. 수문 동시개방 개수, 수문 개방 위치 및 순서, 개방 높이에 대한 조건을 변화시켜 구성한 시나리오에 대해 수치해석 후, 유속, 난류에너지, 이차류 등의 흐름특성을 분석하고 상·하류 수위차에 따른 방류량을 산정하여 시설물의 관리안을 도출하고 운영 매뉴얼의 개정안을 제시하였다.

• Journal of the Korean Association of Geographic Information Studies
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• v.22 no.4
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• pp.158-168
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• 2019

Korea Hydrographic and Oceanographic Agency(KHOA) carried out a research project named 'Marine Fisheries Infrastructure Construction and Technology Training for the Philippines' as part of the 1st Official Development Assistance(ODA) from 2015 to 2018. It is preparing for the 2nd ODA project which will begin in 2020. Besides, recently, the Philippines is paying attention to marine territory management and response capability due to problems such as the sea-level rise and coastal erosion caused by climate change. Therefore, before 2nd ODA to the Philippines, this study analyzed the vertical ocean model on the vertical datum in Korea and suggests the direction of development of the vertical ocean modeling system for the vertical datum in the Philippines using the observed data from the permanent tide station which was built by the Philippines ODA research project over the last four years. Moreover, as a pilot study, the Sulu Sea in the Philippines was selected and analyzed by harmonic analysis method. At each tide station, constants for correction had been computed. And the grid-based tidal model was constructed based on this study. As a result of the study, similar tidal characteristic were observed when the prediction and the measured tide were compared by applying the constants for correction between two station in the sea area with similar tidal level. These results could be used as basic data for the 2nd ODA to the Philippines, and contributed to construct and maintain a close cooperation and friendship between Korea and the Philippines.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.869-875
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• 2016

The purpose of this study is to analyze the long-term wave characteristics and tendencies of coastal waters near Korea based on wave hind-casting modelling. Wave hind-casting modelling was performed with a wind data set from ECMWF (2001~2014), which provides data from 1979 to the present. The results of numerical modelling were verified with observed data collected using wave buoys installed by the Korea Meteorological Administration (KMA) and Korea Hydrographic and Oceanographic Agency (KHOA) in offshore waters. The results agreed well with observations from buoy stations, especially during event periods such as typhoons. The quantitative RMSE value was 0.5 m, which was significant. Consequently, the results of a wave tendency analysis for 14 years (2001~2014) showed an increased appearance ratio for waves of more than 2 m in height at all regional domains. The mean appearance ratio was 0.082 % per year, which implies that coastal waves have been increasing continuously. This coastal wave tendency analysis data can be used to evaluate coastal vulnerability due to recent climate change and the design of coastal erosion prevention structures.

• Journal of the Korean Geographical Society
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• v.42 no.3 s.120
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• pp.368-387
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• 2007

In order to explain geomorphological characteristics of the Korean Peninsula, it is necessary to understand the spatial distribution of tectonic movements and its causes. Even though geomorphological elements which might have been formed by tectonic movements(e.g. tilted overall landform, erosion surface, river terrace, marine terraces, etc.) have long been considered as main geomorphological research topics in Korea, the knowledge on the spatial distribution of tectonic movement is still limited. This research aims to identify the spatial distributions of tectonic movement via sequential analyses of Digital Elevation Model(DEM). This paper first developed a set of terrain analysis techniques derived from theoretical interrelationships between tectonic uplifts and landsurface denudation processes. The terrain analyses used in this research assume that elevations along major drainage basin divides might preserve original landsurfaces(psuedo-landsuface) that were formed by tectonic movement with relatively little influence by denudation processes. Psuedo-landsurfaces derived from a DEM show clear spatial distribution patterns with distinct directional alignments. Lines connecting psuedo-landsufaces in a certain direction are defined as psuedo-landsurface axes, which are again categorized into two groups: the first is uplift psuedo-landsurface axes that indicate the axis of landmass uplift; and the second is denudational psuedo-landsurface axes that cross step-shaped pusedo-landsurfaces formed via surface denudation. In total, 13 axes of pusedo-landsurface are identified in the Korean Peninsula, which show distinct direction, length, and relative uplift rate. Judging from the distribution of psudo-landsurfaces and their axes, it is concluded that the Korean Peninsula ran be divided into four tectonic regions, which are named as the Northern Tectonic Region, Center Tectonic Region, Southern Tectonic Region, and East Sea Tectonic Region, respectively. The Northern Tectonic Region had experienced a regional uplift centered at the Kaema plateau, and the rate of uplift gradually decreased toward southern, western and eastern directions. The Center Tectonic Region shows an arch-shaped uplift. Its uplift rate is the highest along the East Sea and the rate decreases towards the Yellow sea. The Southern Tectonic Region shows an asymmetric uplift centered a line connecting Dukyu and Jiri Mountains in the middle of the region. The eastern side of the Southern Regions shows higher uplift rate than that of the western side. The East Sea Tectonic Region includes south-eastern coastal area of the peninsula and Gilju-Myeongchun Jigudae, which shows relatively recent tectonic movements in Korea. Since this research visualizes the spatial heterogeneity of long-term tenonic movement in the Korean peninsula, this would provide valuable basic information on long-term and regional differences of geomorphological evolutionary processes and regional geomorphological differences of the Korean Peninsula.

• The Journal of the Acoustical Society of Korea
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• v.32 no.1
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• pp.14-21
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• 2013

The erosion, suspension, and transport of sediment frequently occur in the coastal waters and estuarine. These processes often generate the so-called fluid mud layer, which is defined as a high-concentration aqueous suspension of fine grained sediment (> 10 g/l), consisting mainly of silt and clay-size particles. Therefore the high-resolution ultrasound is mostly used to detect or monitor the fluid mud layer. Because the sound attenuation tends to increase rapidly with the suspended sediment concentration, it is necessary to consider the accurate attenuation correction to estimate the backscattering strengths from the suspended sediment layers. In this paper, the volume backscattering strengths with various suspended sediment concentrations were measured using 5-MHz ultrasound signal in a small-scale water tank. The sound attenuation due to the viscosity and scattering from suspended sediment particles was predicted by the Richard's model and applied to the sonar equation to estimate the volume backscattering strengths from the suspended sediment concentrations. For the case that the additional attenuation was not considered, the volume backscattering strengths increased to the concentration of 20 g/l, and over this point, the backscattering strengths were roughly constant. However, for the case that the attenuation due to the suspended sediment concentration was considered, the backscattering strengths increased with the concentration.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.335-349
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• 2017

Submerged breakwaters installed under the water surface are a representative coastal structure to prevent coastal erosion, and various types of submerged breakwaters have been proposed and discussed so far. Generally, submerged breakwaters make the complex wave fields due to abrupt change in water depth at the crown of the breakwater. In this study, wave heights and mean water level formed around a breakwater are examined numerically for three-dimensional permeable submerged breakwaters. OLAFOAM, CFD open source code, is applied in the numerical analysis, and the comparisons are made with available experimental results on the permeable upright wall and the impermeable submerged breakwater to verify its applicability to the three-dimensional numerical analysis. Based on the applicability of OLAFOAM numerical code, the wave height and mean water level distribution formed around the permeable submerged breakwaters are investigated under the formation condition of salient. The numerical results show that as the gap width between breakwaters decreases, the wave height in the center of the gap increases, while it decreases behind the gap, and the installing position of the breakwater from the shoreline has little influence on the change of the wave height. Furthermore, it is found that the decrease of the mean water level near the gap between breakwaters increases with decreasing of the gap width.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.3
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• pp.3-10
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• 2010

The development of various spatial information and GIS has led to the research on interpretation of natural phenomena and correlational studies. This study is aimed to analyze the correlation between RUSLE(Revised Universal Soil Loss Equation) around Nakdong River area during the period of 1955 to 2005 and the amount of area change in the islets at the estuary terrain calculated in the study "Change Detection at the Nakdong Estuary Delta using Satellite Image and GIS". For the calculation of RUSLE, The 'Revised-USLE' model, a modified USLE model commonly used in Korea was used. For the rainfall erosion factor to calculate and compare the area of islets, the actual observation data for one year before the observation of satellite image from all observatories across Korea was used. The correlation coefficient between RUSLE and area change of islets was 0.57 for Jinwoo Islet; 0.7 for Sinja Islet; 0.87 for Doyodeung. This results showed that there was a great influence from Doyodeung where the main water way of Nakdong River runs. This study showed that the study using USLE for various fields and through identifying the characteristics of each factor is useful to understand natural phenomenon in practice.

• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.3
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• pp.48-62
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• 2018

In this study, landslide of debris flow occurred at 51 sites around Daeryounsan located in between Chuncheon-si and Hongcheon-gun during July in 2013 were investigated in field and behavior characteristics of debris flow were analyzed on the basis of records of rainfall and site investigation. According to debris flow types of channelized and hill slope, location and slope angle of initiation and deposit zone, and width and depth of erosion were investigated along entire runout of debris flow. DEM(Digital Elevation Model) of Daeryounsan was constructed with digital map of 1:5,000 scale. Land slide hazard was estimated using SINMAP(Stability INdex MAPping) and the predicted results were compared with field sites where debris flow occurred. As analyzed results, for hill slope type of debris flow, predicted sites were quite comparable to actual sites. On the other hand, for channelized type of debris flow, debris flow occurrence sites were predicted by using stability index associated with topographic wetness index. As analyzed results of 4 different conditions with the parameter T/R, Hydraulic transmissivity/Effective recharge rate, proposed by NRCS (Natual Resources Conservation Service), predicted results showed more or less different actual sites and the degree of hazard tended to increase with decrease of T/R value.

• Journal of the Korean Geographical Society
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• v.49 no.1
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• pp.1-17
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• 2014

This study estimates geomorphological processes of fluvial terraces by uplifts and bedrock features, by the analyses of topography, distribution, formation age and incision rate of fluvial terraces using Gwang-cheon River in Uljin, Namdae-cheon River in Pyeonghae and Osip-cheon River in Yeongdeok located in the southern Taebaek Mountain Range. The tectonic and climatic terraces I in the upper reaches of Gwang-cheon River with an altitude from riverbed of 9~12m indicate the formation age of MIS 2 with a incision rate of 0.40m/ka. However, the tectonic and climatic terraces I in the upper reaches of Osip-cheon River with an altitude from riverbed of 7~10m show the formation age of MIS 3 with an incision rate of 0.10m/ka. These results suggest that the uplift rate in the Gwang-cheon River basin is likely to be higher than that in the Osip-cheon River basin. Unlike the lower reaches of Osip-cheon River, the thalassostatic terraces are not found in the lower reaches of Gwang-cheon River, because the basin has low maintainable ability of landforms in river valley due to high uplift rate and bedrock properties resistant to weathering and erosion. On the other hand, the lowest tectonic and climatic terraces in the study areas indicate different formative ages and the terraces during the cooling stage in interglacial as well as during interstadial are also found. Therefore, this study suggests that chronological method for fluvial terrace by the previous developmental model of climatic terrace should be reconsidered.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.493-500
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• 2019

In this study, sensitivity analysis of sediment transport scaling factors in Delft3D-Morphology was performed to examine the effect those parameters on simulation results of cross-shore profile changes. For numerical experiments, one-year wave time series data which were observed in 2018 on the Maengbang coast in Gangwon prefecture were applied as external force. Bathymetric data observed in January and October of the same year were used as initial bathymetric data and annual bathymetric change data, respectively. The simulation performance of the model was evaluated based on the Brier Skill Score index for each part by dividing an arbitrary cross section within the calculation domain into the onshore and offshore parts. As a result, it was found thet the f_BED variable has a slight effect on the simulation results. The f_BEDW and f_SUSW variables show good simulation performance in onshore part when the value less than 0.5 is applied and vice versa. Among the experimental conditions, the optimal combinations of variables are f_BED = 1.0, f_BEDW = 1.0, f_SUSW = 0.1 for the onshore region and f_BED = 1.0, f_BEDW = 1.0, f_SUSW = 0.5 for the offshore region. However, since these combinations were derived based on the observation data on Maengbang beach in 2018, users should be careful when applying those results to other areas.