• Journal of the Korean Geotechnical Society
• /
• v.26 no.11
• /
• pp.5-15
• /
• 2010

Debris flow is defined as water mixture flow with wide range of large size soil particles such as rock, gravel and sand. Localized heavy rain, derived from abnormal weather, results in the debris flow which generally occurs in summer, especially during and after rainy season and typhoon. This study focuses on the characteristics of impact force of the debris flow with different gravels and gravel mixtures by model experiment. Based on measured experiment results, it is found that the impact force derived by debris flow is mot proportional to the amount of dry material mixture, but depends on the particle size distribution of the debris flow.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.8 no.2
• /
• pp.151-163
• /
• 2003

In this study, we investigated the physiochemical characteristics of temporal estuarine environment formed during the summer flood season (consecutive rainy days with average 50 mm day$^{-1}$ precipitation) in the coastal area of South Sea of Korea. The freshwater from the Seomjin River was characterized by lower temperature, salinity and pH, and high concentrations of COD and nutrients. In the summer flood season, such peculiar Somejin-River freshwater was dispersed southward along the coast of Yeosubando-Dolsando-Geumodo, form-ing temporal estuarine environment (defined as "Coastal Pseudo-Estuary" in this study) throughout the entire study area (as far as 60 km from the Seomjin River mouth). Compared to the winter dry season, the DIN/DIP ratio was almost doubled (16-36) during the summer flood season. This excessive nitrate supply during the summer flood season was probably due to nitrogenous fertilizer. Distribution and behaviors of physiochemical factors in this coastal pseudo-estuarine environment were controlled not only by the runoff of the Seomjun River (physical mixing of river water with seawater) but also by the biogeochemical estuarine processes which are mostly similar to those of the river estuary.r estuary.

• Journal of Korea Water Resources Association
• /
• v.36 no.5
• /
• pp.787-797
• /
• 2003

The characteristics of concentrations and loads of Total Nitrogen(T-N), Total Phosphorus(T-P), and Chemical Oxygen Demand (COD) in mountain stream water were examined from September 2000 through August 2001. The 92.5-ha study watershed in Chungbuk Province consists of 59% mixed forest and 30% coniferous forest. Streamflow was measured and water samples were collected at about 10 day intervals for dry days and at 2-6 hour intervals for a storm event at the study watershed outlet. The mean concentration of COD in streamflow for rainy days was significantly (p < 0.05) higher than for dry days. The mean concentrations of T-N and T-P in vegetation growing season (May to October) were lower than those in vegetation dormant season (November to April). Low concentrations of pollutants during vegetation growing season are likely due to the heavy demand for nutrients by the vegetation and biological activity associated with a warming of soil. The ratios of pollutants loads during storm periods to annual pollutants loads were 87% for T-N, 83% for T-p, and 87% for COD. The unit loads of pollutants for study area were estimated at 5.9 kg/ha $\cdot$ yr for T-N, 0.15 kg/ha $\cdot$ yr for T-p, and 23.9 kg/ha $\cdot$ yr for COD. The removal efficiency of pollutants in study area were 24% for T-N, 58% for T-P and 66% for COD, indicating that a study area shows water purification function.

• Fisheries and Aquatic Sciences
• /
• v.25 no.7
• /
• pp.380-389
• /
• 2022

Morphometric relationships, condition factor (CF) and reproductive biology are significant tools in fish stock management, fish biology, physiology, conservation and ecology. Growth and reproductive strategy of Oreochromis niloticus were studied from 343 fish specimens collected from Lake Shala between January and December 2018. Fish samples ranged from 7.7 cm to 33.0 cm in total length (TL) and from 7.80 g to 708.21 g in total weight (TW) were collected using gillnets of 4, 6, 8, 10, and 12 mm mesh sizes. The length-weight relationship of O. niloticus was TW = 0.0104TL^3.19, indicating positive allometric growth of the fish. The sex ratio (0.93:1) was insignificant from the ideal fish distribution of 1:1 (χ² = 0.47, p > 0.05). Mean CF for males, females and combined sexes was 1.04, 1.06 and 1.05, respectively and statistically insignificant (p > 0.05). The spawning peak occurred in July (rainy) and February (dry) periods, as defined by ripe females and the breeding season. Absolute mean fecundity was 806 eggs and correlated positively with TL and TW of the fish (p < 0.05) (F = 0.56TL^2.29, R² = 0.93, p < 0.05; F = 18.83TW^0.67, R² = 0.90, p < 0.05). The study provides the first detailed account of the morphometric relationships and reproductive biology of O. niloticus in Lake Shala, which can be used as baseline information for successive biological-based studies in Soda Lakes of Ethiopia.

• Journal of Ecology and Environment
• /
• v.37 no.1
• /
• pp.1-11
• /
• 2014

To understand the effects of fluctuations in dam discharge due to river environments and phytoplankton communities, we monitored such environments and phytoplankton communities biweekly, from February 2001 to February 2002 and from February 2004 to February 2005, in the lower Han River (LHR), South Korea. The phytoplankton abundance during the dry season was approximately two times higher than that during the rainy season. In particular, fluctuations in diatom assemblages, which constituted over 70% of the total phytoplankton abundance, were affected severely by the changes in the discharge. When a large quantity of water in a dam was discharged into the LHR, the conductivity and the concentrations of total nitrogen (TN), total phosphorus (TP), and dissolved inorganic phosphorus (DIP) decreased rapidly, whereas the concentrations of suspended solids (SS), dissolved inorganic nitrogen (DIN), and dissolved silica (DSi) increased immediately. Time-delayed relationship also revealed that the dam discharge had an immediately significant negative relationship with phytoplankton abundance. On the whole, fluctuations in phytoplankton communities in the LHR were influenced much more by hydrodynamics such as dam discharge than by the availability of nutrients. Thus, the variability in these concentrations usually parallels the strength of river flow that is associated with summer rainfall, with higher values during periods of high river discharge.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.39 no.1
• /
• pp.25-32
• /
• 2019

The urban river has played an important role in biodiversity by providing various waterside areas in urban areas that are difficult for organisms to live in. The river is also used as a resting place and experience space for citizens. In particular, Yeouido Saetgang is the first ecological park in Korea, and it is located in the heart of downtown Seoul, making it highly valuable for its location and ecological value. However, water quality issues have continuously been raised since the construction project of Yeouido Saetgang river. So it is necessary to investigate the environment state and analyze the causes of the environment deterioration. In this study, the causes of the river stagnation and water quality deterioration in Yeouido Saetgang river were analyzed. For this, river surveys and aerial photo analysis were used to analyze the causes of difficulties in natural water circulation. Also, the results of monitoring water quality showed that the averaged level of BOD and T-P in dry season is III and IV, respectively, while that of BOD and T-P are V~VI in rainy season. In addition, through the drainage analysis of sewer network, small drainages that affect the water quality in Saetgang river was selected and discussed.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1997.06a
• /
• pp.207-231
• /
• 1997

The use household water purifier is continuously increasing due to the distrust of the piped, rap water, which may be caused by the deterioration of water quality and water supply facilities in Korea. The water purifier distributing in the domestic market is the membrane type that composes of membrane as a basic filter, sediment filter as a prefilter and activated carbon filter instead of one purifying water system. The membrane type using as a water cleaning system is mainly the method of micro filtration(NIF) as well as ultra filtration(UF) and reverse osmosis(RO). The types of MF and UF are using to remove suspended solids and virus, and RO is using to remove ionic compound in chemical organic compounds. At the beginning the household water purifier was imported as end-product or assembled by only importing module from small businesses in Korea. Therefore, people was hard to confide in the product quality because the sales policy and management of water purifier by small business were not effectively organized. However, the defects of water purifier having up to now ate improving by the efforts of special branches of water purifier and large enterprises, and new great products are developing and producing. To develop the best quality product of water purifier in Korea, it should be considered seasonal water characteristrics rather than any other condition. For example, the water purifier can be affected by the water temperature change, increase of suspended solids in the rainy season and inflow of raw water having concentration in a dry season. The subject we have to investigate in the future is to develop the water purifying system adaptable in Korea which can treat the water quality using close analyses of local and seasonal water characteristics.

• Journal of the Korean Geosynthetics Society
• /
• v.13 no.1
• /
• pp.63-70
• /
• 2014

This paper describes the influence of rainfall on contamination at stream around the developed quarry. The investigation results are analyzed to evaluate the relationship rainfall and heavy metals (or water pollution). In the relationship rainfall and heavy metals, the result showed that the heavy metal contaminations are caused by boulder stone, waste residue and stone sludge, which is reacted with the direct contamination source, in the burried layer. It also found that the water flow change of stream according to the rainfall increase affected the large effect to a contamination level of heavy metal. the water pollution was increased by time changed from the rainy season to the dry season. That is, a lot of suspended solids had been discharge from the developed quarry due to rainfall increase, and then pollution level of water increases as the undercurrent of suspended solids is generated in stream due to rainfall decrease. Therefore, it analyzed that continuous causes of heavy metal contamination and water pollution in stream are materials in the burried layer and a discharge of pollution source from the developed quarry due to rainfall.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.30 no.5
• /
• pp.207-216
• /
• 2018

This research compared and analyzed safety ratio of slope with Talren97 and SoilWorks based on limit equilibrium analysis and Midas GTS based on finite element analysis. For the analysis variables, there are slope height, berm condition, soil parameter, groundwater level, slope inclination. All of slope stability analysis were performed by dividing into dry season and rainy season. As the result of the analysis of Talren97 and SoilWorks based on same theory, safety ratio of slope shows same value, so there was no difference between the programs. In comparison with limit equilibrium analysis, the result of finite element analysis showed somewhat high ratio of safety and it was higher by about 2.4% averagely. The difference between the result of limit equilibrium analysis and that of finite element analysis is in the range which can ignored in practical work.

• Applied Biological Chemistry
• /
• v.13 no.3
• /
• pp.243-256
• /
• 1970

Nowadays, the damages caused by molds in cotton textile goods becomes influential. In our country, however, the relations between cotton goods and molds are not investigated and studied in detail. Two hundred and fifty seven kind of mold's samples were collected in ninety places through the whole country. The molds samples are mainly gathered according to each regions and seasons from molded cotton textiles. Out of this samples, we isolated six hundred and seventy two strains of molds and the results of isolation are following. 1. The distributed molds were Aspergillus sp., Rhizopus sp., Penicillium sp., etc. among them Aspergillus sp. were most widely distributed, and next were Rhizopus sp., Penicillium sp. etc. 2. The distribution of Aspergillus sp. abounded peculiarly in the dry season, while Rhizopus sp. in the rainy season. 3. The C.M.C, descomposing enzymes forming activity on molds were greatly concerned with intensity damage of cotton textile goods. 4. The formation of C.M.C. decomposing enzyme was only influenced by physiology of each strains. 5. Regarding to the growth. a. The molds which were saprophyting on the cotton textile goods were indicated vigorous growing. b. Among isolated six hundred and seventy two strains, there were above a hundred strains which produced pigment and nearly half of them fifty nine strains were Aspergillus sp. 6. Twenty one strains in isolated six hundred and seventy two strains were indentified which can heavily damage upon cotton textile. As a results of indentification of the selected strains, the following species was abtained, Aspergillus sydowi, wentii, niger, luchuensis, flavus, fumigatus, nidulans, Penicillium frequentants, roqueforti, chrysogenum, albicans, Rhizopus oligosporus, delemar, Mucor rouxii, mucedo, Neurospora sitophila, Monilia variabilis, fructigena, Cladsporium hurbarum and Aspergillus spp. Mucor spp.