• Geophysics and Geophysical Exploration
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• v.16 no.3
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• pp.145-153
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• 2013

High-resolution chirp profiles were analyzed to investigate the echo types of near-surface sediments in the Yellow Sea off the Baegryeong Island. On the basis of seafloor morphology and subbottom echo characters, 7 echo types were identified. Flat seafloor with no internal reflectors or moderately to well-developed subbottom reflectors (echo type 1-1 and 1-2) is mainly distributed in the southern part of the study area. Flat seafloor with superposed wavy bedforms (echo type 1-3) is also distributed in the middle part. Mounded seafloor with either smooth surface or superposed bedforms (echo type 2-1, 2-2, and 2-3) occurs in the middle part of the study area. Irregular and eroded seafloor with no subbottom reflectors (echo type 3-1) is present in the northern part of the study area off the Baegryeong Island. According to the distribution pattern and sedimentary facies of echo types, depositional environments can be divided into three distinctive areas: (1) active erosional zone due to strong tidal currents in the northern part; (2) formation of tidal sand ridges in response to tidal currents associated with sea-level rise distributed in the middle part; and (3) transgressive sand sheets in the southern part. Such a depositional pattern, including 7 echo types, in this area reflects depositional process related to the sea-level rise and strong tidal currents during the Holocene transgression.

• 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.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.3
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• pp.205-212
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• 2015

Farmers with forage barley (Hordeum vulgare L.)-rice (Oryza sativa L.) cropping system at reclaimed tidal lands burn crop residues to facilitate seedbed preparation or remove them for feed stock. This study was conducted to investigate the effect of rice straw amendment and N fertilization on soil properties and N uptake of rice under forage barely-rice cropping system at reclaimed tidal paddy field. Rice straw was applied at the rates of 0, 2.5 and $5.0ton\;ha^{-1}$ and N was fertilized at 0, 100, 200 and $400kg\;ha^{-1}$. Although there was no significant difference in the growth and yield of rice, fresh and dry weight of forage barely increased with increasing the amount of rice straw. The amount of N uptake of rice at harvesting stage was $65.8-69.2kg\;ha^{-1}$ by the amount of rice straw amendment, but there were no significant differences among rice straw amendment levels. After harvesting the rice, the soil salinity decreased with rice straw amendment compared to the control. After forage barely and rice cultivation, soil organic matter contents increased to $2.6-2.8g\;kg^{-1}$ and $3.2-3.5g\;kg^{-1}$, respectively. The amount of N uptake of rice at harvesting stage increased up to $82kg\;ha^{-1}$ in $400kg\;ha^{-1}$ N applied plots which were $37.8kg\;ha^{-1}$ higher than the control. Nitrogen fertilization decreased N recovery efficiency. The highest yield of rice was observed at $244kg\;ha^{-1}$ N fertilization level, but the optimum N level was estimated at $168kg\;ha^{-1}$ in order to keep the protein content of rice under 6.5%. Further researches on N uptake and application of organic matter according to soil salinity will be necessary to increase N use efficiency at reclaimed tidal paddy field.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.67-84
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• 2002

A shallow high-resolution seismic reflection survey was carried out at the Mineopo tidal flat on the western coast of Korea. The purpose of the survey was to investigate shallow sedimentary structure of the tidal (fat associated with the recent sea level change. A total of 795 shots were generated at 1 m interval from a 5-kg hammer source and recorded on 48 channels of 100 Hz geophones along two mutually perpendicular profiles. The water-saturated ground condition resulted in suppressed ground rolls by significantly decreasing rigidity. In addition, seismic velocities over 1500 m/s provided easy segregation of reflected arrivals from lower velocity noise. As a consequence, seismic sections were created that are high in resolution and signal to noise ratio as well. The stack sections show that the tidal flat consists of 5 sedimentary sequences above acoustic basement. Although deposition is largely characterized by the transgressive sedimentary facies resulting from sea level rise, erosional surfaces are well-resolved within the sequences.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.4
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• pp.293-302
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• 1991

The anomalous sea level deviation or storm surge caused by the typhoon Thelma in 1987 are studied analysing tidal observation data at 7 stations in the south coast of Korean peninsula. The surges are calculated by subtracting the predicted tidal height from the observed tidal record. The tidal deviation at these stations along the coast are discussed in association with meteorological data. The sea level anomalies are studied by means of the empirical orthogonal function (EOF) analysis and the fast fourier transform (FFT) method. The results of analysis suggest that the peak value of surges are higher at the tidal stations in semi-enclosed bay and in long narrow channel than at the ones facing with the open sea. From the result of EOF analysis, the temporal and spatial fluctuations of storm surge can be described by the first EOF mode, which explains 63% of the total variances during the passage of typhoon Thelma. The deviation of storm surge in the studied areas indicates bi-modal peak during the passage of typhoon Thelma. From the results of FFT spectrum analysis, the peak of energy of autospectrum for surge, atmospheric pressure, and wind stress appeared at low frequency fluctuations band of 0.008-0.076 cph over the 4 stations. Auto-correlation function of surge showed periodicity, while that of atmospheric pressure and wind stress indicates no periodicity. The result of FFT analysis shows that the typhoon surges are related chiefly with the change of atmospheric pressure in an open bay (Cheju Harbor), but with the wind stress in a semi-enclosed bay (Yeosu Harbor).

• Journal of The Geomorphological Association of Korea
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• v.20 no.4
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• pp.85-99
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• 2013

The objective of this paper is to analyze the spatial distribution of errors in the DEM generated using waterlines from multi-temporal remote sensing data and to assess flood vulnerability. Unlike conventional research in which only global statistics of errors have been generated, this paper tries to quantitatively analyze the spatial distribution of errors from a probabilistic viewpoint using geostatistical simulation. The initial DEM in Baramarae tidal flats was generated by corrected tidal level values and waterlines extracted from multi-temporal Landsat data in 2010s. When compared with the ground measurement height data, overall the waterline-based DEM underestimated the actual heights and local variations of the errors were observed. By applying sequential Gaussian simulation based on spatial autocorrelation of DEM errors, multiple alternative error distributions were generated. After correcting errors in the initial DEM with simulated error distributions, probabilities for flood vulnerability were estimated under the sea level rise scenarios of IPCC SERS. The error analysis methodology based on geostatistical simulation could model both uncertainties of the error assessment and error propagation problems in a probabilistic framework. Therefore, it is expected that the error analysis methodology applied in this paper will be effectively used for the probabilistic assessment of errors included in various thematic maps as well as the error assessment of waterline-based DEMs in tidal flats.

• Korean Journal of Environment and Ecology
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• v.29 no.5
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• pp.743-752
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• 2015

We studied the spatio-temporal microalgal (phytoplankton and benthic diatoms) and environmental changes of the Hajeonri intertidal zone from February to November 2014. Seawater and phytoplankton analysis were conducted all through the months. The species, composition and abundance of phytoplankton and environmental factors were measured. As a result, diatom was dominant among a total of 113 species identified. On a seasonal basis (Feb. May, Aug., Nov.), we carried out studies on benthic diatoms on the surface of the sediments and their habitats at nine stations on the transect line at Hajeonri at low tide. The grain of the surface sediments was mainly composed of sandy silt and sandy mud. Organic pollution level was low. Benthic microalgal biomass (chlorophyll ${\alpha}$) was high in the spring and summer. A total of 163 benthic diatom species were identified. Navicula sp.1 and Paralia sulcata were dominant over the study period. Five diatom species were observed both in water column and on surface sediment at the same time.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.4
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• pp.200-206
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• 2013

Fourier analysis and a wavelet method were carried out to elucidate the characteristics of tidal residual components in coastal waters. The result of Fourier analysis shows tide-induced and monsoon-induced residuals are conspicuous at the short period and mid period, respectively. The tidal residuals were decomposed by period from 3 hours to 8 months and the characteristics of their components were shown by reconstituting them with short periods less than 24 hours, mid-periods between 1 day and 16 days and long periods longer than 1 month. The tidal residuals in the short period, i.e., tide-induced components, being based on the tidal elevation prediction errors, appear in the West Sea with high tidal ranges and do not have much seasonal fluctuation. Additionally, the period of typhoon induced surge ranges more or less than 12 hours. The mid-period components were clearly generated mainly in the West Sea during the winter and largely affected by monsoon. Accordingly, the pure surge height components were concentrated on the mid-period and had clear features for each coastal waters. The long period components show similar characteristics at all stations and are considered to stem from variations of mean sea levels.

• New & Renewable Energy
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• v.4 no.2
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• pp.94-104
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• 2008

The change of water discharge capability of sluice caisson for tidal power plant according to installation of the rubble mound was investigated by performing laboratory experiment. The experiment was carried out in an open channel flume with a great care to measure flow rate and water level in the flume accurately. Eight different sluice caisson models were used in the experiment. The water discharge capabilities of seven sluice models decreased with respect to the placement of the rubble mound, while increased for only one sluice model. On average, the values of discharge coefficient decreased by approximately 10% when the sluice models were placed on the rubble mound. It is concluded that the shape of the rubble mound can affect the water discharge capability of the sluice caisson, so that its shape should be significantly considered in the design of the sluice caisson, especially when it is deployed in a site of relatively deeper depth.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.266-269
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• 2008

In this study, the results of experimental investigation on the water discharge capability of sluice caisson for tidal power plant were presented. In particular, the focus of the study was placed on the examination of change in water discharge capability of a sluice caisson according to the installation of rubble mound. For this purpose, a hydraulic experiment was carried out in an open channel flume with a great care to the measurement of discharge and water level in the flume since they greatly affects the estimation of the discharge capability of each sluice caisson. In the analysis, the experimental data of four different sluice models were used, which showed that the installation of rubble mound affects in different manner depending on each sluice caisson model. When each of the four sluice models were placed on the rubble mound respectively, the water discharge increased for one sluice caisson, whereas decreased for other three sluice caissons. Further detailed analysis is needed to quantitatively estimate the influence of installation of rubble mound on the water discharge capability of a sluice caisson.