• Journal of The Geomorphological Association of Korea
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• v.23 no.1
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• pp.87-101
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• 2016

This study was conducted to develop a hydrological model of catchment water balance which is able to estimate irrigation return flows, so BROOK90-K (Kongju National University) was developed as a result of the study. BROOK90-K consists of three main modules. The first module was designed to simulate water balance for reservoir and its catchment. The second and third module was designed to simulate hydrological processes in rice paddy fields located on lower watershed and lower watershed excluding rice paddy fields. The models consider behavior of floodgate manager for estimating the storage of reservoir, and modules for water balance in lower watershed reflects agricultural factors, such as irrigation period and, complex sources of water supply, as well as irrigation methods. In this study, the models were applied on Guryangcheon stream watershed. R2, Nash-Sutcliffe efficiency (NS), NS-log1p, and root mean square error between simulated and observed discharge were 0.79, 0.79, 0.69, and 4.27 mm/d respectively in the model calibration period (2001~2003). Furthermore, the model efficiencies were 0.91, 0.91, 0.73, and 2.38 mm/d respectively over the model validation period (2004~2006). In the future, the developed BROOK90-K is expected to be utilized for various modeling studies, such as the prediction of water demand, water quality environment analysis, and the development of algorithms for effective management of reservoir.

• Journal of Wetlands Research
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• v.24 no.1
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• pp.52-58
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• 2022

Recently, various efforts and research are being conducted to integrated management of the estuary in Nakdong River. As one of such studies, measurement of opening discharge amount for each floodgate using a three-dimensional fixed ultrasonic flow meter is being conducted, but studies on hydraulic and statistical processing procedures and techniques using actual measurement results for calculating discharge amount by opening remain at the basic level. Therefore, in this study, a data processing technique using three-dimensional fixed ultrasonic flow meter measurement data was developed, the flow coefficient was calculated based on the measured data, and the applicability of the discharge amount calculation formula development was reviewed.

• Journal of The Geomorphological Association of Korea
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• v.18 no.4
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• pp.203-212
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• 2011

The objective of this paper is to identify the present-day surficial sediment distribution patterns of the tidal river, Gongneungcheon, through the grain size and statistical analysis. Four major findings of this study are as follows; First, the composition of sediments over the study area are mainly silt in texture. Second, the surficial sediment distribution reveals that grain size becomes coarser as they approach seawards not only in summer but also in winter. It can be concluded that tidal flows play a significant role, especially in winter, in the distribution of surficial sediments in Gongneungcheon. However, samples obtained in summer were relatively small in mean size and showed better sorting compared to those obtained in winter. Third, the mean sizes of the samples on the transects decrease as the distance from the channel increases. Finally, the artificial structure such as a floodgate affects the distribution of the sediments.

• Journal of Environmental Impact Assessment
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• v.24 no.3
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• pp.287-299
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• 2015

If the Nakdong River estuary is to be sustainable, land use management practices need to consider bird habitat requirements, especially given that the area serves as an important migratory bird sanctuary. In this study, bird habitats found in the Nakdong River estuary were classified into 11 different types including Phragmites australiss, mud flat, farmland, open surface in freshwater, sand bar, riparian forest, Scirpus planiculmis, waterway, construction, grasslands, and open surface in sea or brackish water. Taking into consideration the regional characteristics, habitat properties, and landscape indices, a total of 12 study sites were analyzed. Mud flat, construction, farmland, and P. australis account for 80% of the total land area. The high area ratio of construction and farmland to other types of habitat revealed a high amount of historical human activity and intervention in the area. Both patch numbers as well as patch density were high in West Nakdong River, Samrak Waterfront, Maekdo River, and Daejeo Floodgate, with these areas showing the greatest fragmentation as well. Total numbers of species and individuals had a positive correlation with the area and the number of habitat types. Findings suggest that protecting the habitat area, especially in S. planiculmis, is the most important factor for bird habitat management and that future development could result in habitat loss, having a profoundly adverse impact on bird populations. Therefore, it is important that the total area should be carefully protected by land use regulations in order to ensure that the Nakdong River estuary maintains its functional integrity as a migratory bird sanctuary.

• Journal of Plant Biology
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• v.14 no.4
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• pp.27-33
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• 1971

Information this research an attempt was made to investigate the plant community structure and the process of its formation in the tidal area surrounding Mokpo City the examined area included the stand in Sam-Hak Do wherein sands have inflowed, and the stand in Kat-Ba-Woo which has been left as tidal soil land. Two hundred stands were sampled by making 100m line transects 5m apart and establishing 30cm$\times$30cm quadrates 10m apart on each tape. These data were used to establish frequency, cover degree, density, standing crop (g/$m^2$), contained Cl in the soil, and pH. Results of the research are as following: 1. There were 25 species of plants in the stands from Sam-Hak Do, 18 in the stands from Kat-Ba-Woo, and so 28 species in all. Regardings the importance value, the rank of dominant species is Salicornia herbacea L., Suaeda maritima Dumorties, Diplachne fusca L., Echinochola hispidula Nakai, Cyperus iria L., Setaria lutescens Hubbard in Sam-Hak Do, and Suaeda maritima Dumorties, Echinochloa hispidula Nakai, Aster tripolium L., Scripus maritimus L., Salicornia herbacea L., Diplachne fusca L., in the lands from Kat-Ba-Woo. Among them are five kinds of halophytes Salicornia herbacea L., Suaeda maritima Dumorties, Atriplex Gmelini C.A. Meyer, Aster tripolium L., and Limonium tetragonum Bullock; and two Kinds of naturalized plants Diplachan fusca L., Aster subulata. M. In the stands from Sam-Hak Do there was evidence of a secondary succession phenomena in the presence of Cyperaceae such as Cyperus liria L., Juncus decipiens Nakai, and Fimbristylis longispica Steudal, which could not be found in the stands from Kat-Ba-Woo. 2. On the number of species of vegetation, the further inland from the floodgate the higher the number; that is, the lower the content of Cl the higher the number of species. 3. On the distribution of the vegetation; comparing DFD index and Cl content, the main plants are Salicornia herbacea L., Suaeda maritima Dumorties, Atriplex gmelini C.A. Meyer, Diplachne fuscal, Echinochola hispidula Nakai where the Cl content of soil is more than 13.2%. 4. On the standing crop; Salicornia herbacea L., which has high resistance to salt, was half the total was production of 1090/$m^2$ while Suaeda maritima Dumorties was 1/4, Diplachne fusca L. 1/8, and Echinochloa the least. Analyzing the result, the research indicates that the main factor in plant community formation in tidal land is tolerance for Cl, and that a plan for utilizing the halophytes which are abundant in tidal land should be devised.

• 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.

• Korean Journal of Environmental Biology
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• v.19 no.2
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• pp.159-171
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• 2001

Community structure, horizontal distribution, density, and ratio between nematodes and benthic harpacticoid copepods of the meiobenthos within the sediments of inner Sihwa Lake were investigated in May 1999 and May 2000. A total of 11 and 8 classes of meiobenthic animals were identified in 1999 and 2000, respectively, which were much lower than other coastal areas. The dominant animals during both sampling periods was the nematodes, followed by sarco-mastigophorans, nauplius of crustaceans, benthic harpacticoid copepods and polychaetes. These five classes of animals comprised more than 90% of total abundance of neiobenthos presented in the samples. In 2000, a lot of polychaete larvae were identified. The most abundant animal were the size that fits in 0.063 mm sieve size. Lower density was observed upper inner part of the Sihwa Lake during both sampling periods, and higher density was observed around the Sihwa floodgates. The average density between those two numbers were observed in the samples collected in the middle of the lake. Lower nematodes to betnhic harpacticoides (N/C) ratio, a relative indicator of environmental pollution, was observed to be lower around the floodgate but higher ratios were observed in the upper inner Sihwa Lake. The present study indicated that inner upper part of the lake becomes unsuitable for the meiobenthos, and the most inner upper lake was considered to be polluted.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.8
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• pp.635-640
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• 2009

After 1960s, in accordance with getting bigger in changing range of annual rain precipitation, those dams were built in order to prevent any drought and flood through the regulation of flux. In case of such dam, when it reaches to some definite pondage, for its regulation of water volume, numerous volume of water in the reservoir should be discharged by opening the floodgate, at this time a severe damage can be occurred to those lives and properties of the residents and tourists at the river or riverside. Accordingly, despite the sounding alarm broadcasting for prevention and notice such damage could be clearly travelled to those people without influence by the discharging noise or other neighboring environmental factor, since it was only empirically installed without any peculiar research until now, the alarm broadcasting could not effectively travel, and the travelling distance also could not known correctly. On such point of view, this Study has ever grasped the characteristics by frequencies and its sound pressure level about the discharge noise and the alarm broadcasting of Daechung Dam, one of multipurpose dams through the measurement and analysis by distances, and based on this, also has ever presupposed the proper location of additional alarm broadcasting spot using a simulation program named Cadna-A.

• Korean Journal of Ecology and Environment
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• v.34 no.3 s.95
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• pp.175-184
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• 2001

The temporal and diel changes of cyanobacterial cell density, species composition, and cyanobacterial toxins (microcystin-RR, -YR, -LR) were examined for the outflow water of Lake Suwa in Japan from May to October, 1998. The highest total cell densities of Microcystis were observed in July and September, when the dominant phytoplankton was Microcystis ichthyoblabe and M. viridis, respectively. Both the species composition and total cell density of Microcystis affected the variation of the concentration of three microcystin variants. Only microcystin-RR(MC-RR) and -LR (MC-LR) were detected in July when Microcystis ichthyoblabe dominated, while microcystin-RR, -YR (MC-YR) and -LR were detected in August and October when Microcystis viridis dominated. The microcystin concentration and the cell density of Microcystis in the outflow water showed diel variations; the ratio of maximum to minimum value was $3{\sim}20$ fold far microcystin concentration, and $5{\sim}31$ fold for cell density. The diel variations of toxin concentration as well as Microcystis cell density was closely related to the diel variation of wind. During the windy period, when higher speeds occurred in the afternoon hours than morning hours, both the cell density of Microcystis and microcystin concentration tended to increase in the morning and decrease in the afternoon. The results of this study suggest that controlling the timing of lake discharge at the floodgate or intake tower can be useful for water resource management with respect to decreasing cyanobacteria biomass within intake water.

• Journal of Korean Society of Disaster and Security
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• v.13 no.2
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• pp.39-51
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• 2020

Recently, flood damage has been increasing in Korea due to frequent local torrential rains caused by abnormal weather conditions. According to the calculation of the recurrence period of torrential rain that occurred in North Chungcheong Province on July 16, 2017, it was estimated that the rainfall frequency in the upper are of Goessan Dam was around 1,524 years, and the highest level of Goesan Dam rose to EL.137.60 meters, leaving only 5 cm of margin until the height of the dam floor (EL.137.65 meters). The Goesan Dam, which operated for 62 years since 1957, needs to be prepared to cope with the increase of floodgate volume in the basin, the development of a single purpose dam for power generation only, and there are no measurement facilities for flood control, so efficient operation methods are needed to secure the safety of residents in upper and lower regions. In this study, a method of dam operation was proposed by constructing a rain matrix for quick decision making in flood prediction, calculating the highest level of dam for each condition in advance, and preparing a survey table, and quickly finding the level corresponding to the conditions in case of a situation.