• Journal of Korean Society on Water Environment
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• v.24 no.4
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• pp.442-451
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• 2008

We analyzed characteristics of rainfall-runoff for the channel of Yongwon area made by a new port construction. And we conducted inundation analysis on the region of lower elevation near the coast. SWMM5 was calibrated with the storm produced by the typhoon Megi from August 19 to August 20 in 2004, and was verified with the storm from August 22 to August 22 in 2004. We performed hydraulic channel routing of Yongwon channel about typhoon Megi from August 19 to August 20 in 2004 by UNET model which is a hydraulic channel routing. The simulated runoff hydrographs were added to the new stream as lateral inflow hydrographs and a watershed runoff hydrograph was the upstream boundary condition. The downstream boundary condition data were estimated by the measured stage hydrographs. The maximum stage that was calculated by hydraulic channel routing was higher than the levee of inundated region in typhoon Megi. Thus we can suppose an inundation to have been occurred. We performed inundation analysis about typhoon Megi from August 19 to August 20 in 2004 and flood discharge of return period 10~150 years. And we estimated each inundation area. The inundation areas by return periods of storms were estimated by 3.4~5.7 ha. The causes of inundation are low heights of levee crests (D.L. 2.033~2.583 m), storm surges induced by typhoons and reverse flow through the coastal sewers (D.L. -0.217~0.783 m). A result of this study can apply to establish countermeasure of a flood disaster in Yongwon.

• Journal of Korean Society of Rural Planning
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• v.20 no.4
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• pp.145-155
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• 2014

Since greenhouse gas emissions increase continuously, the authorities have needed climate change countermeasure for adapting the acceleration of climate change damages. According to "Framework Act on Low Carbon, Green Growth", Korean local governments should have established the implementation plan of climate change adaptation. These guidelines which is the implementation plan of climate change adaptation should be established countermeasure in 7 fields such as Health, Digester/Catastrophe, Agriculture, Forest, Ecosystem, Water Management and Marine/Fisheries. Basically the Korean local governments expose vulnerable financial condition, therefore the authorities might be assessed the vulnerability by local regions and fields, in order to establish an efficient implementation plan of climate change adaptation. Based on this concepts, this research used 3 methods which are LCCGIS, questionnaire survey analysis and analysis of existing data for the multiphasic vulnerable assessment. This study was verified the correlation among 7 elements of climate change vulnerability by 3 analysis methods, in order to respond climate change vulnerability in rural areas, Seocheon-gun. If the regions were evaluated as a vulnerable area by two or more evaluation methods in the results of 3 methods' comparison and evaluation, those areas were selected by vulnerable area. As a result, the vulnerable area of heavy rain and flood was Janghang-eup and Maseo-myeon, the vulnerable area of typhoon was Janghang-eup, Masan-myeon and Seo-myeon. 3 regions (i.e. Janghang-eup, Biin-myeon, Seo-myeon) were vulnerable to coastal flooding, moreover Masan-myeon, Pangyo-myeon and Biin-myeon exposed to vulnerability of landslide. In addition, Pangyo-myeon, Biin-myeon and Masan-myeon was evaluated vulnerable to forest fire, as well as the 3 sites; Masan-myeon, Masan-myeon and Pangyo-myeon was identified vulnerable to ecosystem. Lastly, 3 regions (i.e. Janghang-eup, Masan-myeon and Masan-myeon) showed vulnerable to flood control, additionally Janghang-eup and Seo-myeon was vulnerable to water supply. However, all region was evaluated vulnerable to water quality separately. In a nutshell this paper aims at deriving regions which expose climate change vulnerabilities by multiphasic vulnerable assessment of climate change, and comparing-evaluating the assessments.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.3
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• pp.214-227
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• 2021

The distribution of tidal current and tidal induced residual current, topographical eddies and tidal residual circulation in the waters surrounding the Geumo Island-An Island channel were identified through numerical model experiments and vorticity balance analysis. Tidal current flows southwest at flood and northeast at ebb along the channel. The maximum flow velocity was about 100-150 cm/s in neap and spring tide. During the flood current in the neap tide, clockwise small eddies were formed in the waters west of Sobu Island and southwest of Daebu Island, and a more grown eddy was formed in the southern waters of Geumo Island in the spring tide. A small eddy that existed in the western waters of Chosam Island during the ebb in neap tide appeared to be a more grown topographical eddy in the northeastern waters of Chosam Island in spring tide. Tidal ellipses were generally reciprocating and were almost straight in the channel. These topographical eddies are made of vorticity caused by coastal friction when tidal flow passes through the channel. They gradually grow in size as they are transported and accumulated at the end of the channel. When the current becomes stronger, the topographic eddies move, settle, spread to the outer sea and grow as a counterclockwise or clockwise tidal residual circulation depending on the surrounding terrain. In the waters surrounding the channel, there were counterclockwise small tidal residual circulations in the central part of the channel, clockwise from the northeast end of the channel to northwest inner bay of An Island, and clockwise and counterclockwise between Daebu Island and An Island. The circulation flow rate was up to 20-30 cm/s. In the future, it is necessary to conduct an experimental study to understand the growth process of the tidal residual circulation in more detail due to the convergence and divergence of seawater around the channel.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.97-97
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• 2020

Flooding in urban areas is caused by heavy rains for a short period of time and drains within 1 to 2 hours. It is also characterized by a small flooding area. In addition, flooding is often caused by various and complex causes such as land use, basin slope, pipe, street inlet, drainage pumping station, making it difficult to predict flooding. Therefore, this study analyzes the effect of each basin characteristic on the occurrence of flooding in urban areas by correlating various basin characteristics, whether or not flooding occurred, and rainfall(Limit Rainfall), and intends to use the data for urban flood prediction. As a result of analyzing the relationship between the imperviousness and the urban slope, pipe, threshold rainfall and limit rainfall, the pipe showed a correlation coefficient of 0.32, and the remaining factors showed low correlation. However, the multiple correlation analysis showed the correlation coefficient about 0.81 - 0.96 depending on the combination, indicating that the correlation was relatively high. In the future, I will further analyze various urban characteristics data, such as area by land use, average watershed elevation, river and coastal proximity, and further analyze the relationship between flooding occurrence and urban characteristics. The relationship between the urban characteristics, the occurrence of flooding and the limiting rainfall amount suggested in this study is expected to be used as basic data for the study to predict urban flooding in the future.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.1
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• pp.16-25
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• 2012

To calculate the total mass flux that change in dry and flood season in the Yeomha Channel of Gyeonggi Bay, the 13 hour bottom tracking observation was performed from the southern extremity. The value of the total mass flux(Lagrange flux) was calculated as the sum of the Eulerian flux value and stroke drift value and the tidal residual flow was harmonically analyzed through the least-squares method. Moreover, the average during the tidal cycle is essential to calculate the mass flux and the tidal residual flow and there is the need to equate the grid of repeatedly observed data. Nevertheless, due to the great differences in the studied region, the number of vertical grid tends to change according to time and since the horizontal grid differs according to the transport speed of the ship as a characteristic of the bottom tracking observation, differences occur in the horizontal and vertical grid for each hour. Hence, the present study has vertically and horizontally normalized(sigma coordinate) to equate the grid per each hour. When compared to the z-level coordinate system, the Sigma coordinate system was evaluated to have no irrationalities in data analysis with 5% of error. As a result of the analysis, the tidal residual flow displayed the flow pattern of sagging in the both ends in the main waterway direction of dry season. During flood season, it was confirmed that the tidal residual flow was vertical 2-layer flow. As a result of the total mass flux, the ebb properties of 359 cm/s and 261 cm/s were observed during dry and flood season, respectively. The total mass flux was moving the intertidal region between Youngjong-do and Ganghwa-do.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.759-770
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• 1997

The general flow patterns in the Cheju Strait have been investicated by analyzing the current observations measured in $1986\~1989$ by current meter mooring in 3 north-south sections in the Cheju Strait and at 4 observation points around Cheju Harbour, and measured in $1981\~1987$ by drogue tracking. 1. In the Cheju Strait, there are eastward or northeastward residual currents, which implies that sea waters flow into through the whole western section and flow out through the whole eastern section in the Cheju Strait. The velocity of residual currents are $5.2\~30\;cm/sec$ in 10 m layer and $1.3\~24cm/sec$ in mid-bottom layer. Generally, the flow is strong along the deepest through and the northern part, and weak in the shallow areas near Chuja Islands and Bogil Island. 2. In the western entrance of the Cheju Strait, the observed mean residual velocity is 6.93 cm/sec and the volume transport is 0.384 Sv. There are a big discrepancy between the observed residual currents and the geostrophic currents. 3. Near the frontal areas northwest to Chuja Islands, warm and saline offshore waters, flow northward about 5 miles into the southern coastal areas of the Korean Peninsula in flood, and flow back rather eastward or southeastward than southward in ebb. So, warm and saline waters flow along coastal areas, being mixed with coastal waters. As a result, the northwestern area of Chuja Islands plays a role of the entrance of influx of warm and saline offshore water to the southwestern coastal areas of the Korean Peninsula. It should be stressed that this flow pattern is not due to the residual flows, but to the temporal (tidal) flows.

• 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 Korean Society of Coastal and Ocean Engineers
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• v.14 no.3
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• pp.201-208
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• 2002

The characteristics of suspended sediment transport are analyzed at the estuaries which show significant shallow water tides, following the previous research for bottom sediment transport at the same estuaries. Several theories which are related with the formation and transition of turbidity maximum are reconfirmed by the numerical experiments. The experiments suggest the necessity of modeling the shallow water tide as a boundary condition, as was also suggested for the bed sediment transport at the previous research. Both the differences of transport characteristics between bed and suspended sediment and the differences between flood/ebb dominances and high/low water dominances are also examined at the Keum River and Youngsan River estuaries. In addition, the transport of bed and suspended sediments are found to have the opposite directions at the Youngsan River estuary which has extensive tidal flat, and thus shows pronounced ebb dominance, which is considered to be a main reason of keeping present bathymetry.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.6
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• pp.352-358
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• 2014

Hourly tide-gauge data at 10 tide stations along the West/South coasts were analysed statistically for tidesurge interaction. Interactions were found at all stations except Busan, prominently at the western tip of the South coast near Mokpo and Wando. A well-known interaction pattern which occurs at flood tide was found rarely at domestic coasts, while another pattern of the tide-modulated surge which occurs at low tide was detected frequently. In addition, a new interaction pattern which occurs at ebb tide is discovered. This pattern is found at Mokpo where the ebb dominance is prominent. Finally, the skew surge could be considered as a tool coping with such interactions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.3
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• pp.140-148
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• 2014

A storm surge barrier is a specific type of floodgate, designed to prevent a storm surge or spring tide from flooding the protected area behind the barrier. A surge barrier is almost always part of a larger flood protection system consisting of floodwalls, dikes, and other constructions. Surge barriers allow water to pass under normal circumstances but, when a (storm) surge is expected, the barrier can be closed. Among the various means of closing, buoyant flap typed storm surge barrier which was indicated by MOSE project in Italy is chosen for Masan bay protection, and the motion of the surge barrier under the action of storm surge and wave is examined using FLOW-3D, a computational fluid dynamics software analyzing various physical flow processes. Numerical result shows that storm surge barrier is successfully operated under wave height 3 m, and tidal range 2 m.