• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.235-245
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• 2021

Recently, the frequency of torrential rain is increasing due to climate change, which causes a large amount of debris flows. The purpose of this study was to understand the flow characteristics of debris flow according to the change in channel slope and volumetric sediment concentration and to analyze the effects of a berm on the flow characteristics of debris flow. The flow characteristics of debris flow, such as flow velocity, flow depth, Froude number, and flow resistance coefficients, were calculated using laboratory tests. The effect of a berm was analyzed by comparing the experimental results of a linear channel with those of a one-stepped channel. The results showed that the channel slope affected the flow velocity and flow depth, and the volumetric sediment concentration affected the flow velocity and flow depth, Froude number, and flow resistance coefficient. Moreover, as a berm was installed, the flow velocity and flow depth decreased by up to 26.1% and 71.2%, respectively. This means that installing a berm reduces the flow velocity, thereby reducing the mobility and kinetic energy. These results provide useful information to understand better the flow characteristics of debris flow and the effectiveness of a berm.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.2
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• pp.17-29
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• 1983

The siltation of the Gun-San New Harbour is a serious problem to keep the available water depth of the basin. So, in order to make clear the behaviour of the suspended load flowing in and out of the Gun-San New Harbour obviously, the samples of the suspended load at the appropriate points were collected in the estuarine area near the Harbour and at the same time the tidal current velocities measured. Their suspended load concentrations and salinities were analyzed, and emphasis has been placed on the characteristics of the suspended load concentrations and on the relationship between the concentration and the tidal flow as well as the wave. As a result, the authors obtained the followings; 1) The main source of the suspended load in the Geum River estuarine area is transported from its upstream during floods and deposited rapidly due to the salt water, and the settled sediment is resuspended due to the tidal flow and the wave action, transported and settled again. Such a process is periodically repeated according to the tidal curve. 2) The concentrations are, in general, becoming larger with the increase of the tidal range and the wave height, and vice versa. Especially, the concentrations are relatively large in the winter season of which the wave height is larger than another seasons.

• Korean Journal of Weed Science
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• v.17 no.4
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• pp.400-406
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• 1997

Greenhouse studies were conducted to evaluate the tolerance of 42 pepper cultivars to postemergence applications of bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide]. Cultivars, Jopoong, Singsing House, Sweet Green, Kwangbok, and Ilcheon showed relatively tolerant response to bentazon, while cultivars, Dahhong, Early Glory, Korea, Cheongyang, Nostalgia, and Daejanggyeong were susceptible ones to it. At rates over 2.40 kg ai/ha, the tolerant cultivars appeared to be clearly or more tolerant than the susceptible cultivars. For the determination of growth inhibition by bentazon, the concentration required to reduce growth by 50% (GR_(50)) was 2.00 to 2.40 kg ai/ha for susceptible cultivars, and 10.00 to 12.00 kg ai/ha for tolerant cultivars. Moreover, the herbicide rate required to inhibit growth by 50% $(I_{50})$ was 2.40 kg ai/ha for susceptible cultivars and 9.60 kg ai/ha for tolerant cultivars, respectively. On the $I_{50}$ and $GR_{50}$ estimates of growth, the tolerant cultivars were 5- to 6-fold more tolerant to bentazon than susceptible ones.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.1
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• pp.52-62
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• 2014

As a case study of the changed aquatic environment due to an estuary dam, the Geum River Estuary Dam System (GREDS) has been investigated for the last two decades. We sought the similarities and differences in the disrupted aquatic environment between the estuarine and lacustrine sides of the GREDS. Both sides of the GREDS shared similar aquatic disruptions, such as elongated hydraulic residence times, deteriorated water quality, highly accumulated organic-rich sediments, and considerable siltation of river-transported materials prior to reaching coastal waters. The disruptions of water quality such as high nutrients concentration and frequent bloom of blue-green algal are much more noticeable in the reservoir than in the estuary. However serious siltation problem has been reported from the estuary, which will possibly threaten the proper functioning of the natural Kunsan Estuarine System.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1006-1015
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• 2010

We studied sea water pollution by opening the water gate of Bunam Lake in Seosan City. SS and COD were simulated. If we control the flow rate to 100ton/s, and the gate opening time to 3 hours, SS of 50ppm can be clear with in 19hours. Also, COD of 8ppm can flow for 1 hour without damaging total sea water(COD less than 2ppm). Thus, If we control the flow rate and flow time, the fish cultivation will be free from danger of water pollution.

• Journal of Environmental Impact Assessment
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• v.28 no.5
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• pp.457-470
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• 2019

This study aims to present the characteristics of marine physics, water quality, and sediment quality around offshore wind farm near the Gochang and Buan sea areas through the analysis of monitoring data. The relationships between suspended solid and wave height as well as suspended solid and flow velocity were analyzed. We found that Correlation Coefficient values of 0.61~0.69 between wave height and suspended solid, and suspended solid concentration reaches 75 mg/L or higher when wave height of more than 1m occurred in the spring (1 month). The water quality index (WQI) was used to identify the status of the water quality in the study area. Most of the measured points were rated first grade (very good). The variation of chlorophyll-a was relatively hight compared to the other criteria, indicating that it is a major factor affecting the quality index. In the sediment column, all heavy metals were detected below the Threshold Effects Level(TEL), and ignition loss and grain size show a positive correlation.

• Journal of Korea Water Resources Association
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• v.37 no.11
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• pp.897-913
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• 2004

There has been continuous efforts to manage the water resources for the required water quality criterion at river channel in Korea. However, we could not obtain the partial improvement only for the point source pollutant such as, wastewater from urban and industrial site through the water quality management. Therefore, it is strongly needed that the Best Management Practice(BMP) throughout the river basin for water quality management including non-point source pollutant loads. This problem should be resolved by recognizing the non-point source pollutant loads from upstream river basin to the outlet depends on the land use and soil type characteristic of the river basin using the computer simulation by distributed parameter model based on the detailed investigation and the application of Geographic Information System(GIS). Used in this study, Annualized Agricultural Non-Point Source Pollution (AnnAGNPS) model is a tool suitable for long term evaluation of the effects of BMPs and can be used for un gauged watershed simulation of runoff and sediment yield. Now applications of model are in progress. So we just describe the limited result. However If well have done modeling and have investigated of propriety of model, well achieve our final goal of this study.

• Journal of Environmental Impact Assessment
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• v.24 no.5
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• pp.444-455
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• 2015

In relation to the utilization and disposal of dredged sediment caused by coastal dredging project, we diagnosed the status of legal standard and system, and proposed the improvement plan. Dredging costal sediment distinguished the usage and the disposal by the Standard for the Beneficial Usage of Dredged Sediment. The site where disposal has been completed could be used as a site for developmental project. In case of the usage of dredged sediment for reclamation, we found that the adaptation of the Standard for Beneficial Usage of Dredged Sediment is appropriate for reclamation considering the characteristic of soil, the differences of variables, and the distinction of standard analysis methods. The current the Standard for Beneficial Usage of Dredged Sediment requires the improvement with the usage of dredging coastal sediment in the following. First, the Standard needs to include the standard of the discrimination for reclamation. Second, the current Standard is necessary to be divided by two levels, it needs to be mitigated considering human health risk. Third, it is necessary to consider both the marine environmental impact assessment and mitigation plan near coastal dredging area.

• Applied Biological Chemistry
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• v.43 no.2
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• pp.124-129
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• 2000

Nitrogen and P in surface runoff and eroded sediment from cropland areas can contaminate streams and lakes. Runoff losses of N and P were determined in a small field plot $(14.3{\times}24.8\;m)$ of peach orchard from March to November in 1999. Nitrogen and P were applied in the rate of 172 and 46 kg/ha using chemical fertilizer and mixed oil cake fertilizer. During the season, in 26 rainfall events, $421.5\;m^3/ha$ of runoff including 1,989 kg/ha of soil loss was collected. Concentrations of total-N, $NO_3-N$, $NH_4-N$, total-P and $PO_4-P$ in runoff samples were in the range of $4.7{\sim}171.0,\;0.1{\sim}188.0,\;0.13{\sim}3.36$, $0.58{\sim}4.99$ and $0.05{\sim}3.71\;mg/l$, respectively. Total loss of N was 16.39 kg/ha and 75% of the loss was $NO_3-N$. Total loss of P was 1.04 kg/ha, and $PO_4-P$ and sediment bound P accounted for 47 and 27% of the total loss, respectively. The losses of N and P were about 9.5 and 2.3% of the applied N and P in the plot, respectively. Although the loss of N or P would be relatively small in agricultural aspect, considering the high concentrations of N and P in runoff, loss of N and P from croplands should be controlled to reduce the eutrophication problem of stream waters.

• Korean Journal of Food Science and Technology
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• v.48 no.5
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• pp.496-501
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• 2016

This study was conducted to minimize the quality degradation of concentrated blueberry juice after $90^{\circ}C$ treatment for 5 min by means of citric acid (CA) and acidic sodium metaphosphate (ASM) as pH modifiers. The highest anthocyanin content was observed at 1% CA+1% ASM (65.747 mg per 100 g) followed by 1% CA (46.022 mg per 100 g) and control (30.864 mg per 100 g). The DPPH radical scavenging activities of 1% CA+1% ASM, 1% CA and control were 87.338, 75.486 and 67.983% in respectively. The elastase inhibitory activity at 1% CA+1% ASM, 1% CA and in the control was 87.338, 75.486 and 67.983%, and the tyrosinase inhibitory of these samples were 77.891, 67.598 and 26.375%, respectively. Anthocyanin contents, DPPH radical scavenging, elastase inhibitory and tyrosinase inhibitory activities were significantly different (p<0.05) between the 1% CA+1% ASM treatment and control. During the heat treatment, quality degradation of concentrated blueberry juice was reduced by the 1% CA+1% ASM treatment, as expected for new acidulants.