• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.4
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• pp.9-14
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• 2007

This study reviewed the behavior(movement) characteristics of floating marine debris flowing in the Nakdong River Estuary using a simple numerical particle-tracking model on the conditions of the maximum water discharge outflow from the Nakdong River barrage during the passage of typhoon Maemi in 2003. The simulation showed that the particle distribution and movement of floating marine debris in the Nakdong River Estuary reached a stable state at 72 hours after the typhoon had passed, during the flood period of river discharge. The quantity of floating particles distributed on the east coast of Gadeok and Jinu Islands increased by 40% at 33 hours after starting the model, while the change in other sea areas was 20-40%.

• Proceedings of KOSOMES biannual meeting
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• 2007.11a
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• pp.23-28
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• 2007

This study estimated the behavior(movement) characteristics of floating marine debris flowing in the Nakdong River Estuary using a simple numerical particle-tracking model. This numerical experiment considered the maximum water discharge outflow from the Nakdong River barrage during the passage of typhoon Maemi in 2003. The simulation showed that the particle distribution and movement of floating marine debris in the Nakdong River Estuary reached a stable state at 72 hours after the typhoon had passed, during the flαxl period of river discharge. The quantity of floating particles distributed on the east coast of Gadeok and Jinu Islands increased by 40% at 33 hours after starting the model, while the change in other sea areas was $20{\sim}40%$.

• Korean Journal of Remote Sensing
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• v.39 no.2
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• pp.193-205
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• 2023

A large amount of floating debris from land-based sources during heavy rainfall has negative social, economic, and environmental impacts, but there is a lack of monitoring systems for floating debris accumulation areas and amounts. With the recent development of artificial intelligence technology, there is a need to quickly and efficiently study large areas of water systems using drone imagery and deep learning-based object detection models. In this study, we acquired various images as well as drone images and trained with You Only Look Once (YOLO)v5s and the recently developed YOLO7 and YOLOv8s to compare the performance of each model to propose an efficient detection technique for land-based floating debris. The qualitative performance evaluation of each model showed that all three models are good at detecting floating debris under normal circumstances, but the YOLOv8s model missed or duplicated objects when the image was overexposed or the water surface was highly reflective of sunlight. The quantitative performance evaluation showed that YOLOv7 had the best performance with a mean Average Precision (intersection over union, IoU 0.5) of 0.940, which was better than YOLOv5s (0.922) and YOLOv8s (0.922). As a result of generating distortion in the color and high-frequency components to compare the performance of models according to data quality, the performance degradation of the YOLOv8s model was the most obvious, and the YOLOv7 model showed the lowest performance degradation. This study confirms that the YOLOv7 model is more robust than the YOLOv5s and YOLOv8s models in detecting land-based floating debris. The deep learning-based floating debris detection technique proposed in this study can identify the spatial distribution of floating debris by category, which can contribute to the planning of future cleanup work.

• Journal of Fisheries and Marine Sciences Education
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• v.11 no.2
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• pp.203-215
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• 1999

Floating debris was recorded from a training ship, Kaya, of Pukyong National University with about 12 knots speed at July 19~21, 1999 and July 24~26. The sampled area is the Yellow Sea (YS) connected from Cheju Is. of Korea to Qindao harbor of China, divided into 88 unit segments on survey routes. Debris fabrication materials were categorized with 6 items using the following; man-made or natural wood items, paper and cardboard, nylon netting and rope, styrofoams, vinyl and plastics, floating metal and glass containers. All identified items within a $120{\pm}20m$ wide band were recorded but ignored if beyond this boundary. The results of distribution of floating debris in the area are as follows: 1. The greatest quantities of marine debris discovered during the survey were $184pieces\;per\;km^2$ near Qindao harbor. The next polluted areas, Sohuksan islands, positioned in the eastern part of YS were scattered in about $40pieces/km^2$ or so. 2. Among items, woods, paper and cardboard, vinyl and plastics were found out near Qindao Coast of China. On the other hand, there were many styrofoams, nylon netting and rope near the area of Sohuksan islands in the eastern part of YS. 3. The distribution densities of western part of YS near Qindao are varied with largely range in items and quantities but those of the eastern part, near Sohuksan islands were nearly constant. 4. Styrofoams were composed of 63% among all debris in YS, next paper and cardboard 15%, and wood item, vinyl and plastics each 10%. Therefore, marine debris of YS is revealed that distribution characteristics and composition are very different in each area. These phenomena are concluded that they largely depend on the life styles in land and the utilities of the sea. And of items, styrofoams is dominated by the distribution pattern of YS. Furthermore, surveys are continuously being investigated, and from this it is hoped that a much wider coverage can be achieved, perhaps all sites of the YS and contributed to the finding sources, the stationary area and removal method of debris joined the flow patterns.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.815-829
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• 2008

Debris flows are a natural hazard which looks like a combination of flood, land and rock slide. Large rainfall in July 2006 produced several large scale debris flows and many small debris flows that resulted in loss of life and considerable property and railway damage, as was widely reported in the national media. The hazard "debris flow" is still insufficiently researched. Furthermore debris flows are very hard to predict. Flexible Ring net barriers are multi-functional mitigation devices commonly applied to rock fall or floating wood protection in floods, snow avalanches and also mud flows or granular debris flows, if properly dimensioned for the process or processes for which they are intended. Overtopping of the barriers by debris flows and sediment transport is possible, supporting the design concept that a series of barriers may be used to stop volumes of debris larger than are possible using only one barrier. The future for these barrier concepts looks promising because these barriers represent the state of art for such applications and are superior to many other available options.

• Journal of Fisheries and Marine Sciences Education
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• v.23 no.4
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• pp.642-647
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• 2011

In order to analyze the influence of floating marine debris (FMD) in the East China Sea (ECS), a sighting survey was conducted from July 1st to July 14th, 2009 navigating about 966 km using a training vessel "Kaya (1,737 ton)" of Pukyong National University. The sampled zones are divided into 5 transect by observation day during the survey days and again specified with 45 segments per unit hour on the survey routes. The results of distribution of FMD are as follows: 1. The quantities of FMD at the central China Sea(CE) and northern part of Taiwan(NT) were found as total mean of 90.8 ea/hr, 56.7 ea/hr, respectively, and also 36.8 ea/hr, western part of Kyushu district(WJ), 10.7 ea/hr, 8.0 ea/hr, western(OK1) and northern part(OK2) of Okinawa, respectively. 2. Temporal variation of FMD is represented by depicting the sinusoidal curve as shape as tide in CE and OK1. 3. The higher sea surface temperature (SST) is as likely as if Kuroshio current exists strongly, the less quantities are decreased. On the other hand, the coastal zone of ECS and near of Yellow Sea are increased by lower SST.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.6
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• pp.1358-1365
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• 2014

This study is to analyze the variability of floating marine debris(FMD) on the Kuroshio Current Area(KCA). A sighting survey was conducted from July 5th to July 16th, 2013 while navigating on KCA from Keelung, Taiwan to Tokyo, Japan using T/V KAYA of Pukyong National University. The sampled zones were divided into 6 transects and observed FMD during daytime in each transect. And also specified with 56 segments by defined one hour tracking distance as one segment on the survey routes. The results are as follows: 1. Hourly deviation of FMD's quality in each transect goes up to 10 times at NT, HS and SK. The others 3 times or so. 2. During the surveys, the largest amounts of it were found as total mean of $31.0num(ea)/km^2$ at NT transect in the northern part of Taiwan. So it is estimated because this area has gotten out of KCA. 3. And also quality of it on KCA was not directly related to Kuroshio Current's strong or weak. In conclusion, For the more detailed results on KCA are required of much more surveys.

• Korean Journal of Remote Sensing
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• v.30 no.1
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• pp.127-136
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• 2014

When the mouth of the Nakdong River, opens its floodgate, thousands of tons of litter should flown into the South Sea, moving towards nearby coast, thus causing serious social and economic damage. For this reason, in the present study, research was performed on one certain area in northeast coast of Geoje island, which is assumed as area damaged due to rainy season and typhoon in 2012, and research for trace of movement route was implemented by using buoy to identify characteristic of movement of floating debris caused from Nakdong River. Flows related to the movement of floating debris was also identified by analyzing ocean meteorological environment. As a result of the study, total 40 tons of litter composed of grasses and trees(or plants litter) were flown into Heungnam beach on 16th, Jul which is the rainy season. Plus, the location tracking buoy, which was dropped when the typhoon SANBA was coming, was passed by southern sea of Gadeok-do and was flown into Geoje beach 1 ~ 2 days after it was dropped. The wind direction was mostly northeasterly wind around the Geoje beach at the time the buoy and floating debris were flown into northeast coast and there was common sea surface currents which was flowing into the coast.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.208-215
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• 2017

When persistent oil, such as crude oil or Bunker C oil, is spilled at sea, viscosity increases through the weathering process. Equipment that can collect this oil when mixed with floating marine debris is very limited. In this study, devices that can be attached to the outside of existing oil skimmers have been applied to the inside of the main body, to develop an unmanned conveyor belt type floating marine debris and high viscosity oil recovery skimmer, which is composed of a conveyor belt, a sweeper with a forced inflow device, and a collection tank equipped with a buoyant body. The resulting skimmer was operated at a speed of 1.2 knots at a distance of 30 m in a sea area test. It was stable when moving laterally in any direction. An oil recovery performance test was conducted using a portable storage tank, and oil was recovered from a minimum of $7.8k{\ell}/h$ to a maximum of $23.3k{\ell}/h$. Moreover, recovery of $7.7k{\ell}/h$ was obtained in a wave water tank test with floating marine debris such as PET bottles and oil mixed. If the equipment developed in this study was used in the field for oil pollution accidents, it could be expected to contribute to improved response capability. We believe our equipment could be used in further studies to improvement the performance of existing portable oil skimmers.

• Journal of the Korean GEO-environmental Society
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• v.11 no.8
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• pp.15-23
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• 2010

Debris flows are a natural hazard which looks like a combination of flood, land and rock slide. Large rainfall in July 2006 produced several large scale debris flows and many small debris flows that resulted in loss of life and considerable property and railway damage, as was widely reported in the national media. The hazard "debris flow" is still insufficiently researched. Furthermore debris flows are very hard to predict. Flexible Ring net barriers are multi-functional mitigation devices commonly applied to rock fall or floating wood protection in floods, snow avalanches and also mud flows or granular debris flows, if properly dimensioned for the process or processes for which they are intended. Overtopping of the barriers by debris flows and sediment transport is possible, supporting the design concept that a series of barriers may be used to stop volumes of debris larger than are possible using only one barrier. The future for these barrier concepts looks promising because these barriers represent the state of art for such applications and are superior to many other available options.