• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.4
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• pp.495-508
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• 2019

Tidal datums are key and basic information used in fields of navigation, coastal structures' design, maritime boundary delimitation and inundation warning. In Korea, the Approximate Lowest Low Water (ALLW) and the Approximate Highest High Water (AHHW) have been used as levels of tidal datums for depth, coastline and vertical clearances in hydrography and coastal engineering fields. However, recently the major maritime countries including USA, Australia and UK have adopted the Lowest Astronomical Tide (LAT) and the Highest Astronomical Tide (HAT) as the tidal datums. In this study, 1-hr interval 19-year sea level records (1999-2017) observed at 9 tidal observation stations along the west and south coasts of Korea were used to calculate LAT and HAT for each station using 1-minute interval 19-year tidal prediction data yielded through three tidal harmonic methods: 19 year vector average of tidal harmonic constants (Vector Average Method, VA), tidal harmonic analysis on 19 years of continuous data (19-year Method, 19Y) and tidal harmonic analysis on one year of data (1-year Method, 1Y). The calculated LAT and HAT values were quantitatively compared with the ALLW and AHHW values, respectively. The main causes of the difference between them were explored. In this study, we used the UTide, which is capable of conducting 19-year record tidal harmonic analysis and 19 year tidal prediction. Application of the three harmonic methods showed that there were relatively small differences (mostly less than ±1 cm) of the values of LAT and HAT calculated from the VA and 19Y methods, revealing that each method can be mutually and effectively used. In contrast, the standard deviations between LATs and HATs calculated from the 1Y and 19Y methods were 3~7 cm. The LAT (HAT) differences between the 1Y and 19Y methods range from -16.4 to 10.7 cm (-8.2 to 14.3 cm), which are relatively large compared to the LAT and HAT differences between the VA and 19Y methods. The LAT (HAT) values are, on average, 33.6 (46.2) cm lower (higher) than those of ALLW (AHHW) along the west and south coast of Korea. It was found that the S_a and N₂ tides significantly contribute to these differences. In the shallow water constituents dominated area, the M₄ and MS₄ tides also remarkably contribute to them. Differences between the LAT and the ALLW are larger than those between the HAT and the AHHW. The asymmetry occurs because the LAT and HAT are calculated from the amplitudes and phase-lags of 67 harmonic constituents whereas the ALLW and AHHW are based only on the amplitudes of the 4 major harmonic constituents.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.333-333
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• 2011

배수갑문 외측에 발생하는 유사 퇴적 현상으로 인하여 배수갑문의 통수능이 감소하게 되는데, 이로 인하여 홍수 배제 능력과 조수 차단 능력이 감소하여 간척지의 홍수 피해와 침수 피해 등이 발생할 위험성이 증가한다. 본 연구에서는 대천 방조제 배수갑문 외측에 발생하는 유사 퇴적현상을 규명하기 위해, 3차원 수치 모형인 EFDC(Environmental Fluid Dynamics Code) 모형을 이용하여 모의하였다. 격자망을 구성하기 위해서 SMS(Surface Water Modeling System) 모형을 이용하여 배수갑문이 위치하고 있는 방조제에 대한 격자체계를 구성하였다. 격자체계는 직교좌표계를 사용하여 4269개의 격자를 만들어 모형에 적용하였다. 수위 및 유량에 대한 경계조건은 기상자료, 조위관측소 자료, 배수갑문 운용자료를 통해 구축하였으며, 초기조건은 보령 조위자료를 이용하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.3
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• pp.217-227
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• 2012

On 31 March 2007, the abnormal wave occurred along western coast of Korean including Yeonggwang. In this paper, this event is studied using available field measurement data for the event analysis and numerical model for reproducing the unknown waves. We found several 1-min interval tidal elevation and mean sea level pressure (MSLP) data along the western coast of Korea and analyzed it using wavelet technique. We computed the arrival time and the propagation direction of abnormal wave using wavelet results and performed the numerical simulation using 2 dimensional shallow water wave model. The sea level under the forcing of air pressure jump was obviously amplified by the Proudman resonant effect. The computed sea levels compared with observations are underestimated, but the order of arrival time at the tidal station showed good agreement.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.6
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• pp.222-232
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• 2022

In this study we investigated the characteristics of long-term tidal constituents based on 30 tidal gauge data along the coasts of Korea and its the effects on total water level (TWL) forecasts. The results show that the solar annual (Sa) and semiannual (Ssa) tides were dominant among long-term tidal constituents, and they are relatively large in western coast of Korea peninsula. To investigate the effect of long-term tidal constituents on TWL forecasts, we produced predicted tides in 2021 with and without long-term tidal constituents. The TWL forecasts with and without long-term tidal constituents are then calculated by adding surge forecasts into predicted tides. Comparing with the TWL without long-term tidal constituents, the results with long-term tidal constituents reveals small bias in summer and relatively large negative bias in winter. It is concluded that the large error found in winter generally caused by double-counting of meteorological factors in predicted tides and surge forecasts. The predicted surge for 2021 based on the harmonic analysis shows seasonality, and it reduces the large negative bias shown in winter when it subtracted from the TWL forecasts with long-term tidal constituents.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.320-320
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• 2020

하천이용을 위한 다양한 개발사업이 이루어지고 있고 대규모 보가 설치되면서 과거와는 다른 변화된 수리조건에서 기존의 방법으로는 유량자료 생산이 더욱 어려워졌기 때문에 자동유량측정시설의 필요성이 증대되어 조위나 배수 영향을 받는 지점에서 기존 방식을 대체하거나 보완할 수 있는 새로운 유량측정방법으로 자리매김하게 되었다. 자동유량측정시설은 2020년 4월 현재 기준으로 한강 19개소, 낙동강 23개소, 금강 10개소, 영산간 10개소 총 62개소가 운영 중이다. 하지만 4대강 사업 이후, 수질 문제 등의 이유로 2017년 6월부터 순차적으로 4대강 보를 개방하여 보 운영수위에 따라 유속측정이 곤란한 관측소가 증가하고 있으며 이로 인해 환경부 수자원정보센터에서는 보 운영 별 최저수위에서도 자동유량측정시설 운영이 가능하도록 시설물을 개선하는 사업을 실시하고 있다. 개선사업 기간 동안 자료생산의 공백이 발생하지 않도록 인력에 의한 유량측정성과를 확보하여 관측소별 대안유량 산정방법을 개발하였다. 개발된 대안유량은 관측소 개선공사 기간뿐만 아니라 보 운영에 따른 수위저하로 인한 미계측 기간에도 적용하여 유량자료의 손실을 최소화 하도록 하였다. 2019년 운영현황을 범위로 전체 관측소 62개 중 4대강 보 구간에서 관측소 개선공사 8개소와 수위 저하로 유속측정이 불가능한 12개소 중 수위-유량관계곡선식 적용이 가능한 2개소를 제외한 10개소를 대상으로 평균 76일 결측이 발생한 것에 대해 대안유량 산정방법을 적용하여 전 기간 유량자료를 보완하였다. 그 결과 전체 2019년 자동유량측정시설 유량산정률은 99.8%로 자료생산의 공백을 최소화 할 수 있었으며 향후, 보 구간 자동유량측정시설 개선이 완료된 후에도 장비 이상 또는 이상치 발생 시에도 대안유량 산정방법을 활용하여 자료생산의 공백을 최소화 할 수 있을 것으로 기대하고 있다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.365-373
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• 2013

Representative tidal gauging (TG) stations are selected to cover the tidal characteristics of the Korean peninsula coastal seas, and the statistical parameters of the data are analysed from the perspective of the probability distribution at that TG station. The shape of the distribution in the Incheon and Gunsan TG stations, which are tide-dominated areas, shows two clear modes at HWONT and LWONT in the distributions, and in the Mokpo station, shows an asymmetric double peak distribution. In contrast, the frequency distribution shape shows a smoothed flat peak in the Jeju, Yeosu and Busan TG stations, and a single peak in the Pohang and Sokcho TG stations. The emersion and submersion equations suggested as the 6-parameter Gaussian mixture models in this study are accurate, and well fitted to the observed tidal elevation data. The ${\mu}_1$, ${\mu}_2$ parameters are highly correlated to the LWONT and HWONT, and the ${\sigma}_1$ and ${\sigma}_2$ parameters are also closely correlated to the mean tidal range. The ${\mu}_1$ and ${\mu}_2$ parameters coincide with the modes of the suggested probability distribution of the hourly tidal level data.

• Journal of Korea Water Resources Association
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• v.33 no.5
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• pp.635-645
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• 2000

In tidal rivers, the river level, discharge and tide are interrelated. Therefore, the stage-discharge relation that takes no account of tidal effects is inaccurate. For the calculation of river discharge in low water level, this paper attempts to formulate a multiple regression equation of stage-discharge curve to calculate the river discharge in low water level with variables as river level and differences between sea level and river level. Numerical application were perfonned on Ulsan gaging station in Taehwa river, and the comparison with existing rating curve equation showed good applicability of this multiple regression equation.uation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.1
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• pp.11-18
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• 2022

In order to improve the accuracy of particle tracking prediction techniques near the Korean Strait, this study compared and analyzed a particle tracking model based on a seawater flow numerical model and a machine learning based on a particle tracking model using field observation data. The data used in the study were the surface drifter buoy movement trajectory data observed in the Korea Strait, prediction data by machine learning (linear regression, decision tree) using the tide and wind data from three observation stations (Gageo Island, Geoje Island, Gyoboncho), and prediciton data by numerical models (ROMS, MOHID). The above three data were compared through three error evaluation methods (Correlation Coefficient (CC), Root Mean Square Errors (RMSE), and Normalized Cumulative Lagrangian Separation (NCLS)). As a final result, the decision tree model had the best prediction accuracy in CC and RMSE, and the MOHID model had the best prediction results in NCLS.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.8
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• pp.570-578
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• 2014

A three-dimensional ocean circulation model was applied to a shallow estuary, Mobile Bay, to study local wind setup and setdown. Tides started from the northern Gulf of Mexico propagates up to the Mobile River system which is located in the north of the Mobile Bay. However, the tides started in the south of Mobile Bay were distorted when travelling upstream while affected by river discharge and local winds. The water surface elevation was less/over predicted responding north/south winds, respectively, when winds only at the Dauphin Island station (DPI) were used. However, the model predicted water surface elevation better when using two local winds from DPI and Mobile Downtown Airport (MDA). Wind speeds were greatly reduced (~ 88%) in about 43 km distance between DPI and MDA, and the canopy effects may be the reason for this. For this reason, the local winds are greatly responsible for local surface elevation setup and setdown especially at the shallow estuary like Mobile Bay.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.6
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• pp.391-405
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• 2015

A global tsunami prediction system was suggested for a distant tsunami using a finite fault model and a cyclic boundary condition. The possibility of the suggested system as a distant tsunami response system was checked by applying it into the case of 2014 Chile tsunami. A comparison between the numerical results(tsunami height and arrival time) with different conditions (boundary condition, governing equation, grid size and fault model) and measured data (DART buoy, tide station) showed the importance of the finite fault model and the cyclic boundary condition.