• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1427-1431
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• 2007

In this study, the new methodology which combines Kohonen self-organizing map(KSOM) neural networks model and the conventional neural networks models such as feedforward neural networks model and generalized neural networks model is introduced to forecast flood stage in Nakdong river, Republic of Korea. It is possible to train without output data in KSOM neural networks model. KSOM neural networks model is used to classify the input data before it combines with the conventional neural networks model. Four types of models such as SOM-FFNNM-BP, SOM-GRNNM-GA, FFNNM-BP, and GRNNM-GA are used to train and test performances respectively. From the statistical analysis for training and testing performances, SOM-GRNNM-GA shows the best results compared with the other models such as SOM-FFNNM-BP, FFNNM-BP, and GRNNM-GA and FFNNM-BP shows vice-versa. From this study, we can suggest the new methodology to forecast flood stage and construct flood warning system in river basin.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.669-673
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• 2008

In this study, the new methodology which combines Kohonen self-organizing map(KSOM) neural networks model and the conventional neural networks models such as feedforward neural networks model and generalized neural networks model is introduced to forecast flood stage in Nakdong river, Republic of Korea. It is possible to train without output data in KSOM neural networks model. KSOM neural networks model is used to classify the input data before it combines with the conventional neural networks model. Four types of models such as SOM-FFNNM-BP, SOM-GRNNM-GA, FFNNM-BP, and GRNNM-GA are used to train and test performances respectively. From the statistical analysis for training and testing performances, SOM-GRNNM-GA shows the best results compared with the other models such as SOM-FFNNM-BP, FFNNM-BP, and GRNNM-GA and FFNNM-BP shows vice-versa. From this study, we can suggest the new methodology to forecast flood stage and construct flood warning system in river basin.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.963-969
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• 2011

The river-bed sediments from the major river basins were analysed for the chemical and physical properties to evaluate environmental safety for the agricultural uses. The samples were taken from 16 sites of Han river, 36 of Geumgang river, 27 of Yeongsan river, and 140 of Nakdong river. The total of 219 samples from the 28 counties were taken from the surface of the sediments at the depth of 50 cm. The particle density of the sediments was greater than $2.63Mg\;m^{-3}$ and the whole range of the density was $2.60{\sim}2.69Mg\;m^{-3}$, the average particle size was 0.7 mm whereas the size range was 0.075~0.85 mm. The analyses of the particle sizes by basins showed that Han and Geumgang river had particle sizes of 0.075~0.85 mm, while Geumgang and Yeongsan river had particle sizes of 0.25~0.85 mm. Geumgang and Yeongsan river tended to have greater particle sizes. The average values of the chemical properties were 6.3 for pH, $0.16dS\;m^{-1}$ for EC, $8g\;kg^{-1}$ for organic matter, $101mg\;kg^{-1}$ for available phosphate, 0.39, 3.47, and $0.93cmol_c\;kg^{-1}$ for exchangeable potassium, calcium, and magnesium respectively. The greatest property at each basin was pH for Han river, Ec, available phosphate and exchangeable sodium for Geumgang river, organic matter, exchangeable calcium and magnesium for Yeongsan river, and exchangeable potassium for Nakdong river.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.3
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• pp.407-415
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• 2018

This study analyzed the role of dams for the flood control by the observed and simulated hourly flood discharge data. The study area was the Nakdong river basin with Andong and Imha dams. For the analysis 31 flood events from 1997 to 2010 were selected. In the analysis of the flood reduction rate (FRR) of dam itself, the FRR was not decreased with higher size of floods which is not as we expected. In order to see the trend of flood reduction rate depending on the flood size, flood discharge volume presents it better than peak flood discharge. In the comparison of the flood reduction effects of the two dams, Andong dam has 7% larger flood reduction influence at the Sungju gauging station (SGS) located farthest from the selected watershed. Comparing the ratio of the watershed area based on the covered size of the SGS, the FRR of dam is smaller than the area rate. The impact of FRR of dam showed that the FRR fell below 10% when reaching the size of watershed area corresponding to 8.5 times of the size of watershed area of the dam which is larger than Namhan river basin (7 times).

• Journal of the Korean association of regional geographers
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• v.16 no.2
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• pp.85-99
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• 2010

This study analyzes the geomorphic environments of river channels and properties of sediments in the Naeseong-River basin, a branch of Nakdong-River. While the area at NU1 located in the uppermost reaches indicates the landscapes with the gravel riverbeds, the sand riverbeds can be seen in the downstream of NU2 whose basin consists mostly of the granite regolith. The downstream of NU2 has the braided channels in the beds and this may be due to the large quantities of sand particles supply to the bed under the favorable geologic and geomorphic conditions, properties of river flowing within the floodplains less resistant to the erosion and great fluctuations of discharges. Whereas the river at NU2 may seem that sand particles are actively eroded during the high water-level periods, the particles may be actively deposited during the periods at NM2 and NL2. Moreover, in the reaches of NU2 to NM1 and NL1 to NL2, the mean grain sizes of sediments increase downstream suggesting the other supplies of coarse sediments from the lower order streams running the steep slopes because the river flows in the areas consisting of the metamorphic rocks rather than the granites and shows the properties of incised meander.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2245-2254
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• 2013

A vulnerability index was developed for drought by using trend analysis and Delphi method. Twelve indicators were selected based on three groups, i.e., hydrological, meteorological, and humanistic groups. Data were collected from Nakdong river watershed. Three trend tests, i.e., Mann-Kendall, Hotelling-Pabst, and Sen's trend tests, were performed for standardizing the indicators and Delphi method was used to estimate the weights for individual indicators. The drought vulnerability index was calculated for seven regions in the Nakdong watershed and Hapcheon turned out to be the most vulnerable region among the study regions. The drought vulnerability index developed in this study can be applied to other regions in Korea for establishing national water resources management plan.

• Journal of the Korean earth science society
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• v.37 no.4
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• pp.211-217
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• 2016

There have been found mine tailings, wastes, and mining drainage scattered in the area of Nakdong River due to the improper maintenance of the abandoned mines. These contaminants can flow into rivers during the heavy rain periods in summer. Along the study area beginning Seokpo-myeon, Bonghwa-gun of Gyeongsangbuk-do untill Dosan-myeon, Andong-si, there are one hundred five mines including sixty metalliferous mines and forty-five nonmetal mines, which can adversely affect the adjacent rivers. To verify the contamination, we collected sediments, seepage water and surface water for a year both in rainy season and dry season. This study found that sediments, containing high concentrations of heavy metals caused by mining activities, are dispersed throughout the entire river basin (68 sample points with pollution index, based on the concentration of trace element, (PI) >10 among the total of 101 samples). The results of river water analysis indicated the increased concentrations of arsenic and cadmium at branches from Seungbu, Sambo, Okbang and Janggun mine, which concerns that the river water may be contaminated by mining drainage and tailing sediments. However, it is difficult to sort out the exact sources of contamination in sediments and waters only by using the chemical compositions. Thus the control of mining pollution is challenging. To prevent water from being contaminated by mining activities, we should be able to divide inflow rates from each origin of the mines. Therefore, there should be a continued study about how to trace the source of contaminants from mining activities by analyzing stable isotopes.

• Journal of Microbiology and Biotechnology
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• v.24 no.4
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• pp.556-562
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• 2014

The occurrence of human norovirus (NoV) genogroup I (GI) and genogroup II (GII) strains was investigated in Korea. Between 2007 and 2010, 265 samples were collected from 89 Korean water source locations. NoV GI was detected in 4.5% and NoV GII in 1.5%. Samples collected in winter had the highest occurrence; 9.4% for NoV GI and 6.3% for NoV GII. NoV GI detection was highest in groundwater, with the next highest in river water and the lowest in lake water (5.9%, 5.4%, and 1.6%, respectively), and NoV GII was found only in river water. When three representative Korean basin systems (Han (H)-, Geum/Seom (G/S)-, and Nakdong (N)-river basins) were compared, both NoV genogroups were high in the G/S-, but absent in the H- river basin. The most prevalent genotypes within the GI and GII groups were GI.5 and GII.4, respectively. The NoVs found in surface water were identical to those found in patients and those found in groundwater. The NoVs appeared to be transmitted from the patient to the surface water, and then to the groundwater, suggesting a fecal-oral route of transmission. This is the first nationwide surveillance of NoV in major Korean water sources.

• Journal of Korean Society for Geospatial Information Science
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• v.25 no.2
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• pp.49-56
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• 2017

In this study, flood analysis was conducted to prepare for damage caused by typhoons and heavy rain due to abnormal climate and climate change. Two - dimensional flooding analysis using the FLUMEN model, which is widely used for national and international flood risk mapping, was conducted for the Nam River Basin, which is the tributary of the Nakdong River. This study divides the topography into $5m{\times}5m$ DEM by ArcView, so that the accuracy of river repair and hydrological characterization and flood area identification can be maximized. As a result of simulation of water flooding, 163.3ha in section 1, 227.7ha in section 2 and 59.9ha in section 3 were simulated.

• Journal of Korea Water Resources Association
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• v.53 no.3
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• pp.193-200
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• 2020

Hydrological drought is directly associated with lack of available water in rivers, reservoirs, and groundwater. It is important to analyze hydrological drought for efficient water resource management because most of rainfall is concentrated in wet seasons and water supply is highly dependent on dams and reservoirs in South Korea. Generally, a threshold level method is useful for defining hydrological droughts. However, this method causes interdependent problems between drought events which result in skewed results in further statistical analysis. Therefore, it is necessary to determine a proper threshold level to represent regional drought characteristics. In this study, applying 50~99 percentiles of daily flow-duration curve, hydrological drought events were extracted, and independence tests were conducted for 12 watersheds. The Poisson independence test showed that 87~99 percentiles were available for most stations except for Yeoju and Pyeongtaek. The generalized Pareto independence test showed that 80~90 percentiles were the most common. Mean excess plot showed that 80 ~ 90 percentiles were the most common. Therefore, the common ranges of the three independent tests were determined for each station and proper threshold levels were recommended for large river basins; 70~76 percentiles for the Han River basin, 87~91 percentiles for the Nakdong River basin, 86~98 percentiles for the Geum River basin, and 85~87 percentiles for the Youngsan and Seomjin River basin.