• The Journal of the Acoustical Society of Korea
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• v.38 no.1
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• pp.56-65
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• 2019

The Indo-Pacific bottlenose dolphins (Tursiops aduncus) are a toothed whale using echolocation clicks and have been studied continuously abroad. However, most studies on this whale's clicks were performed about captive animals and, in Korea, only the studies of the whistle sounds of this animal were done. In this paper, acoustic characteristics of clicks were analyzed about the free-ranging Indo-Pacific bottlenose dolphins living in the coast of the Jeju Island. Acoustic parameters such as signal duration, 1st and 2nd peak frequency, 3 dB and 10 dB bandwidth for acoustic characteristics were calculated and compared with those of Australian species. As a result, the signal durations had average of $38{\mu}s$ and most clicks were within range of $20{\mu}s-60{\mu}s$. The two types of bandwidths showed both narrowband and broadband characteristics, and bimodal signal characteristics were confirmed through the 1st peak frequencies(average of $96kHz{\pm}18kHz$) and the 2nd peak frequencies(average of $69kHz{\pm}19kHz$).

• Korean Journal of Ichthyology
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• v.33 no.3
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• pp.184-190
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• 2021

Since the original description of new species, Eumicrotremus jindoensis, we confirmed the first occurrence of E. jindoensis based on a single specimen (22.3 mm SL) caught by inshore stow net at the coastal waters of Boryeong of Korea. However, our specimen slightly differed from type specimens in having more vertebrae (26 vs. 21~24), longer snout (17.4% vs. 8.1~9.1%), longer preanus length (67.5% vs. 58.0~58.3%) and shorter second dorsal fin base (15.3% vs. 20.2~20.8%). Comparing with mtDNA COI and Cytb sequences, we could not find any differences in mtDNA Cytb sequences between our specimen and type specimens, which suggest that those morphological differences may belong to local variation by habitat and environmental condition between off Jindo Island and off Boryeong in Korea. Eumicrotremus uenoi is known from the southern sea of Korea narrowly (Busan, Tongyeong, and Jeju Island), the other congeneric species (E. asperrimus, E. pacificus, and E. taranetzi) from only the eastern sea of Korea, but E. jindoensis from the central coast to southern coast of western Korea.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.3
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• pp.122-130
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• 2021

A wind-speed estimation at the arbitrary elevations is key component for the design of the offshore wind energy structures and the computation of the wind-wave generation. However, the wind-speed estimation of the target elevation has been carried out by using the typical functions and their typical parameters, e.g., power and logarithmic functions because the available wind speed data is limited to the specific elevation, such as 2~3m, 10 m, and so on. In this study, the parameters of the vertical profile functions are estimated with optimal and analyzed the parameter ranges using the HeMOSU-1 platform wind data monitored at the eight different locations. The results show that the mean value of the exponent of the power function is 0.1, which is significantly lower than the typically recommended value, 0.14. The values of the exponent, the friction velocity, and the roughness parameters are in the ranges 0.0~0.3, 0~10 (m/s), and 0.0~1.0 (m), respectively. The parameter ranges differ from the typical ranges because the atmospheric stability condition is assumed as the neutral condition. To improve the estimation accuracy, the atmospheric condition should be considered, and a more general (non-linear) vertical profile functions should be introduced to fit the diverse profile patterns and parameters.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.5
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• pp.253-264
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• 2019

Storm surges caused by a typhoon occur during the summer season, when the sea-level is higher than the annual average due to steric effect. In this study, we analyzed the sea-level pressure and tidal data collected in 1 h intervals at Incheon, Kunsan, Mokpo, Seogwipo stations on the Yellow Sea coast to analyze the summer season storm surge and wave overtopping. According to our analyses, the summer mean sea-level rise on the west and south coasts is approximately 20 cm and 15 to 20 cm higher than the annual mean sea-level rise. Changes in sea-level rise are closely related to changes in seasonal sea-level pressure, within the range of 1.58 to 1.73 cm/hPa. These correlated mechanisms generates a phase difference of one month or more. The 18.6 year long period tidal constituents indicate that in 2090, the amplitude of the $M_2$ basin peaks on the southwest coast. Therefore, there is a need to analyze the target year for global warming and sea-level rise in 2090. Wave overtopping was simulated considering annual mean sea-level rise, summer sea level rise, the combined effect of nodal factor variation, and 100-year frequency storm surge. As a result, flooding by wave overtopping occurs in the area of Suyong Bay, Busan. In 2090, overtopping discharges are more than doubled than those in Marine City by the recent typhoon Chaba. Adequate coastal design is needed to prepare for flood vulnerability.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.2
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• pp.162-172
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• 2021

This study was conducted to determine whether the layout of wheelhouse and work environment of coastal improved stow net fishing boats affect the physical abnormalities of wheelhouse workers through a survey and to use it as basic data to improve the wheelhouse work environment. The analysis results are as follows. The result of factor analysis on the wheelhouse work environment was classified into three factors: suitability of work environment, suitability of work space arrangement, and layout of navigational and fishing equipment. The result of factor analysis on physical abnormalities was divided into two factors: physical pain and fatigue. The results of regression model analysis showing factors affecting physical pain showed that the t-value in the regression model was 3.625 (p < 0.05), indicating that the work environment suitability had an effect on the physical pain. Work environment suitability had a significantly positive effect on the physical pain. As work environment suitability increased by 1, the physical pain increased by 0.371 (p < 0.05). The results of regression model analysis showing the influencing factors on fatigue were found to have a t-value of 3.009 (p < 0.05) in the regression model, indicating that the work environment suitability had a significantly positive effect on the feeling of fatigue. It was found that fatigue increased by 0.324 (p < 0.05) as the work environment suitability increased by 1. In addition, the manageability of task suitability was found to be t = -2.521 (p > 0.05). As the manageability of task suitability increased, the skipper's fatigue level decreased. From these results, it is inferred that the wheelhouse of the current coastal improved stow net fishing boats causes physical pain and fatigue for the skippers. In order to reduce such physical pain and fatigue, and to improve safe fishing operation and job satisfaction, it is necessary to provide a wheelhouse to fishermen on coastal improved stow net fishing boats in consideration of the characteristics of the wheelhouse work of fishing boats and in consideration of users.

• Journal of Korea Water Resources Association
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• v.54 no.6
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• pp.433-442
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• 2021

In order to examine the characteristics of tidal wave from the estuary to upsteam of tidal river, tidal asymmetry was identified based on analysis of the harmonic constants of M2 and M4 tidal constituents in the domestic western coastal regions. As shallow water tide is greatly developed in the estuary, flood dominance in Han River and Keum River, and ebb dominance in Youngsan River are developed. These tidal asymmetries can be reconfirmed by analyzing the tidal current data. Unlike having reciprocating tidal current patterns in Keum and Youngsan estuaries, rotaing tidal current pattern is shown in the Han River estuary due to the complex topography and waterways around Ganghwa Island area. However, when residual current is removed, flood dominance is shown in consistency with the tide data. The tidal asymmetry in the estuary tends to intensify with the growth in shallow water tide as the tidal wave propagates to upstream of tidal river. Energy dissipation, in shallow Han River and Keum River classified as SD estuaries, is very large regarding bottom friction characteristics. On the other hand, the deep Youngsan River, classified as a WD estuary, shows less energy dissipation.

• Journal of The Geomorphological Association of Korea
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• v.25 no.3
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• pp.43-55
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• 2018

This study aimed to identify different sedimentary environments of Gochang coast according to geomorphic conditions of each bore hole. To achieve the aim, this study utilized the classification of sedimentary environmental conditions of surface sediment, which was based on grain size distribution characteristics.In other words, three sedimentary environmental conditions ofsandy flat + sand beach, coastal sand dune and weathered bedrock soil, which were distinguished based on grain size distribution characteristics of mean-sorting for surface sediments, were applied to the sediments of bore holes. Four sedimentary environments could be identified in Gochang coast. First, the lake sedimentary environment originated from terrestrial sediments seems to have been dominated by weathered bedrock soil that the surface flow has deposited in a coastal wetland or a boundary, which is affected by the sea. Second, the lake sedimentary environment that is little affected by coastal sand dunes is located at the center of a valley, which is connected to the land, and the dune slack of Saban-ri. The surface flow of weather bedrock soil is the main source of deposits. However, there seems to have been a temporary influence of the sea. Third, the lake sedimentary environment that is strongly affected by coastal sand dunes is located at the dune slack of Yeongjeong-ri. This environment shows traces of a change from a coastal sand dune into the dune slack. Finally, the coastalsand dune sedimentary environment, which wasinvestigated by boring the current coastal sand dune, shows a temporary influence of the land but seems to have maintained the overall stability. Consequently, this study demonstrated that the grain size distribution characteristics of the present surface sediments could be effectively applied to identify the sedimentary environments of the paleo bore hole sediments. In addition, the paleo change of sedimentary environment could also be identified in many places of Gochang coast. If the results of this study are combined with the age dating and geochemical analysis in future works, the paleo environmental change in Gochang coast will be restored more precisely.

• Journal of The Geomorphological Association of Korea
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• v.20 no.4
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• pp.1-13
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• 2013

Padori beach is one of the representative composite mixed beach in Korea and shows divert geomorphic landscape change. It belongs to the Taean National Park. The purpose of this study is to clarify movement mechanism of sediments from sediment distribution of Padori beach associated with morphology. In addition, it is to explain morphological landscape change under different wave and tide condition in the composite mixed beach consisting of a dissipative low tide terrace and a reflective beach face with a high tide range of 5 to 7m. The results of this study are: First, the mean grain size of sediments becomes smaller from the south of the beach, where there is a wide wave-cut platform, to the north because gravels are supplied from the wave-cut platform as well as sea-cliff in the south of the beach. A sedimentation pattern of the sandy gravel on the beach face and gravel on the berm, and gradation phenomena of grain size on cross-shore and alongshore direction in the beach can be explained with a pattern of sediment movement, overpassing, in the composite mixed beach. Second, micro-topography on beach face and berm were changed depending on effects of wave height and tide. As a result, in low-wave energy environments, a berm is developed in large size, and beach cusps are formed on the upper beach face, while in high-wave energy environments, a berm is built up in relatively small size, and mixture of sediments occur on the upper beach face.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.1
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• pp.10-24
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• 2021

A seasonal characteristic of fish assemblages in the coastal waters of Gapa-do was determined using samples collected by a trammel net from 2015 to 2019. Annual mean temperature and salinity were 18.9℃, 33.6 psu (2015), 19.5℃, 33.6 psu (2016), 18.9℃, 33.8 psu (2017), 18.8℃, 34.5 psu (2018) and 19.5℃, 33.7 psu (2019), which show a stable water mass. During the survey period, a total of 50 species (30 families and 8 orders) of fishes were identified, including Scorpaeniformes (3 families and 9 species) and Perciformes (18 families and 29 species) that accounted for 68% of the total number. The number of species was higher in summer than in winter, showing the peak in the summer by 35 species and the low in the winter by 20 species. The number of individuals and the biomass peaked in the summer by 690 individuals and 151.4 kg, and were the lowest in the autumn by 336 individuals and 76.6 kg. The annual diversity index, evenness index and richness index were appeared to be 2.54-2.75, 0.68-0.76 and 5.32-6.65 at each stations. The dominance index was appeared to be the highest in 2018 and the lowest in 2015. Marbled rockfish (Sebastiscus marmoratus), rock fish (Sebastes inermis), filefish (Stephanolepis cirrhifer), rabbit fish (Siganus fuscescens), porcupine fish (Diodon holocanthus) and smallscale blackfish (Girella melanichthys) were dominant species, which occurred abundantly during the entire survey period. Subtropical fishes were identified as a total of 24 species (48.0%) and the number of species was higher in 2019 by 20 (60.6%) species and lower in 2015 by 13 (44.8%) species. The dominant species of the subtropical fishes were appeared to be rabbit fish, porcupine fish, smallscale blackfish, flag fish (Goniistius zonatus), stripey (Microcanthus strigatus), grunter (Parapristipoma trilineatum), and bluestriped angelfish (Chaetodontoplus septentrionalis) at the study sites.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.29-37
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• 2021

In the event of a marine pollution accident, Korea, which is bordered by the sea on three sides, would suffer tremendous damage. According to an analysis of marine pollution accidents in Korea, most pollutants were small fishing boats and tugboats. In particular, urgent safety measures are required due to the high incidence of marine pollution accidents caused by stranded tugboats. This study aims to decrease secondary marine pollution accidents by preparing measures to prevent accidents by stranded tugboats, the main source of pollution accidents. To this end an experiment was conducted to mark 63 locations where stranded accidents have occurred on the GPS plotters of 61 tugboats operating in Boryeong sea area. Its effectiveness was then investigated. The result showed that there was no stranded accident by the subject ship during the 20-month experiment period. As a result of survey of the captains, 36 out of 40 respondents (90%) stated that the experiment was significantly helpful in ensuring safe navigation, thus confirming its effectiveness. Various measures were proposed to prevent stranded accidents, including providing information to manufacturers and users by marking the location of grounded accidents on GPS plotters and posting the location information of unknown reefs on the official website of institution Korea Hydrographic and Oceanographic Agency.