• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.4
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• pp.91-98
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• 2000

The present study is the first attempt involving quantification of the different types of debris found on the seabed of Chinhae Bay in the South Sea of Korea. Eleven cruises were undertaken to collect marine debris samples by bottom trawling from February in 1998 to January in 1999. The tows were conducted over a period of 60-90 min, and eight types of debris were counted: plastic, fishing gear, metallic objects, wood, rubber or leather, glass, textile and the others. Results are obtained based on the number and weight of the objects classified as per eight categories and station for a trawling period. The results of this study are that the number and weight of debris found per unit of swept area (1 hectare) were surveyed as 27.8(1,612 in total) and 3,130 g(193,820 g in total), and plastic and fishing gear have the most composition of marine debris by number, on the other hand, metallic objects and fishing gear have the most composition of marine debris by weight.

• Journal of the Korean Society for Marine Environment & Energy
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• v.4 no.3
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• pp.74-80
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• 2001

Due to floating marine debris, seabed litters, dead shellfishes and polluted sediments, etc. , which are mainly caused by fishery activities in a large scale around the coastline, expansion of industrialized areas from economic development and drastic increase of free time by the improved standard of living, Korean coast is believed to be cast beyond the self purification of marine ecosystem. Seabed litters, if not remedied in a timely manner, will eventually lead to the overall disorder of benthic ecosystem. Thus, in order to prevent marine ecosystem from being thrown into confusion by seabed litters and to restore ocean environments, it is reasonable to investigate the current status of the seabed litters by carrying out an extensive examination on them and to equip ourselves for marine debris with an systemized tool that provides supports to the building process of an efficient methodology of litters disposal through managing related data appropriately. As an primary step to this goal, a systematic method of investigation is presented in this paper. With this methodology, the present state of the seabed titters is properly understood for the specified list of ports.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.295-307
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• 2021

The Korean Peninsula is surrounded on three sides by the East Sea, West Sea and South Sea which are connected to many rivers and streams, thereby facilitating easy inflow of debris from land. Furthermore, excessive debris inflow to the sea because of active fishing and various recreational activities. Debris entering the sea are weighted over time and settle in the seabed, thus, making direct monitoring of debris impossible and its collection difficult. Uncollected submerged marine debris affects the seabed ecosystem and water quality and can cause ghost fishing and ship accidents, especially due to waste net ropes and waste fishing gears. Therefore, understanding the debris distribution characteristics is necessary to assist quick collection of these debris (waste net ropes and waste fishing gears). Thus, this study conducted a survey of debris deposited in the seas of 39 ports. Furthermore, distribution characteristics and compositions of submerged marine debris were identified by a map prepared through GIS-based spatial analysis of the East Sea. Consequently, 58% of waste tires in the East Sea were concentrated in breakwaters and ship berthing facilities. Moreover, 26 % of waste plastics were distributed outside the port. Identifying the distinct distribution characteristics of submerged marine debris was difficult; however, compared with others, the distribution of waste plastics was possible outside the port. The findings of this study can serve as baseline data to assist the collection of submerged marine debris using the distribution characteristics.

• Korean Journal of Remote Sensing
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• v.38 no.6_1
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• pp.1329-1341
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• 2022

Destroying the marine environment and marine ecosystem and causing marine accidents, marine debris is generated every year, and among them, submerged marine debris is difficult to identify and collect because it is on the seabed. Therefore, deep-learning-based semantic segmentation was experimented on waste fish nets and waste ropes using underwater images to identify efficient collection and distribution. For segmentation, a high-resolution network (HRNet), a state-of-the-art deep learning technique, was used, and the performance of each optimizer was compared. In the segmentation result fish net, F1 score=(86.46%, 86.20%, 85.29%), IoU=(76.15%, 75.74%, 74.36%), For the rope F1 score=(80.49%, 80.48%, 77.86%), IoU=(67.35%, 67.33%, 63.75%) in the order of adaptive moment estimation (Adam), Momentum, and stochastic gradient descent (SGD). Adam's results were the highest in both fish net and rope. Through the research results, the evaluation of segmentation performance for each optimizer and the possibility of segmentation of marine debris in the latest deep learning technique were confirmed. Accordingly, it is judged that by applying the latest deep learning technique to the identification of submerged marine debris through underwater images, it will be helpful in estimating the distribution of marine sedimentation debris through more accurate and efficient identification than identification through the naked eye.

• Journal of Ocean Engineering and Technology
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• v.29 no.5
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• pp.373-379
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• 2015

Side Scan Sonar (SSS) is capable of acquiring real-time data for seabed scouring, bathymetry, mine countermeasurement, etc. In a shipyard, an SSS package is utilized to measure the water depth and find debris in the sea because a sufficient water depth and non-interruption have to be ensured before implementing an underwater installation such as a large thruster. This paper presents the application and operation method of an SSS for the construction of an offshore project.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.129-143
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• 2017

The shallow sediments in the southwestern Ulleung Basin consist of mass flow deposits such as slide/slump and debris flow deposits (DFD), caused by slope failure. These sediments are proven to be important in studying geological disaster and stability of the seafloor. In this paper, we analysised the flow accumulation and slope failure susceptibility of the Ulleung Basin on the basis of multi-beam data, collected in this area. We also studied the distribution pattern and the seismic characteristics of the DFD in the uppermost layer of the Ulleung Basin on the basis of seismic data. The slope susceptibility was calculated as the frequency ratio of each factors including slope, aspect, curvature and stream power index (SPI), which causes the slope failure. These results indicate that the slope failure is frequently to occur in the southern and western continental slope of the Ulleung Basin. The sediment flow (mass flow) caused by the slope failure converges to the north and northwest of the Ulleung Basin. According to the seismic characteristics, the uppermost layer in study area can be divided into four sedimentary unit. These sedimentary units develop from the south and southwest to the north and northwest in association with slope susceptibility and flow accumulation.

• Economic and Environmental Geology
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• v.45 no.5
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• pp.513-523
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• 2012

The upper sedimentary layer of the Ulleung Basin in the East Sea shows stacked mass-flow deposits such as slide/slump deposits in the upper slope, debris-flow deposits in the middle and lower slope, and turbidites in the basin plain. Shallow gases or gas hydrates are also reported in many area of the Ulleung Basin, which are very important in terms of marine resources, environmental changes, and geohazard. This paper aims at studying acoustic characteristics and distribution pattern of gas-related structures such as acoustic column, enhanced reflector, dome structure, pockmark, and gas seepage in the upper sedimentary layer, by analysing high-resolution chirp profiles. Acoustic column shows a transparent pillar shape in the sedimentary layer and mainly occurs in the basin plain. Enhanced reflector is characterized by an increased amplitude and laterally extended to several tens up kilometers. Dome structure is characterized by an upward convex feature at the seabed, and mainly occurs in the lower slope. The pockmark shows a small crater-like feature and usually occurs in the middle and lower slope. Gas seepage is commonly found in the middle slope of the southern Ulleung Basin. These gas-related structures seem to be mainly caused by gas migration and escape in the sedimentary layer. The distribution pattern of the gas-related structures indicates that formation of these structures in the Ulleung Basin is controlled not only by sedimentary facies in upper sedimentary layer but also by gas-solubility changes depending on water depth. Especially, it is interpreted that the chaotic and discontinuous sedimentary structures of debris-flow deposits cause the facilitation of gas migration, whereas the continuous sedimentary layers of turbidites restrict the vertical migration of gases.