• Journal of Life Science
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• v.19 no.10
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• pp.1410-1416
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• 2009

The present study aims to examine the effect of turbid water on fishes in streams which branch into a turbid water area (Yeongyang-gun) and a non-turbid water area (Cheongsong-gun), and finally flow into the Imha reservoir. In a comparison of water quality, the chemical status of the water showed higher pH, DO and SS in the turbid water area than in the non-turbid water area. Also, high density of clay minerals such as vermiculite (V) and illite (I), which is from clay mineral leakage during rainfall, was detected in turbid water, resulting in an increase of turbidity. Fishes inhabiting the turbid water showed irregular spaces in gill lamella, cell separation, edema, and clubbing in epithelial tissues. Also, the gill surface showed roughness and plenty of muddy debris substances inside the gills. The Bowman's space was expanded because of contraction of the glomerulus in the Bowman's space of the kidney tissues. Antioxidant enzymes such as SOD, CAT, GPX, and GST showed higher activities in the specific tissues, muscles and kidney, of fishes living in turbid water than in the non-turbid area. We suggested that; first, the antioxidant activities were increased due to removal of harmful radicals generated in fish bodies in the turbid water area, second, long-time exposure of these histological changes in the tissues might have induced secondary lesion accompanying the inaccurate physiological constancy of fishes.

• Journal of Korean Society of societal Security
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• v.2 no.4
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• pp.43-48
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• 2009

During the past few years, Korea has experienced extraordinary floods, which have caused many damages of lives and properties. Flooding caused by typhoon is the most common disastrous phenomenon of nature among all catastrophes. As the average temperature of the earth has been increasing by global warming, the possibility of typhoon is also increased by abnormal climate changes. Along with the river improvement as a part of flood control, the time of concentration has been decreased, so the pick discharge has been increased. Moreover, with the land development activities, the area of storage has been diminishing, and the damages from inundation have been continuously increasing. There were a lot of damages to farmland in 1960's, industrial and public facilities in 1970's, and a lot of sufferings from the windstorm in 1980's. In 1990's, however, the amount of damages was increased substantially. So, there is need to decrease the number of the victims and loss of properties by applying preventive measures against natural calamities. This study has employed a simulation system to calculate the depth and amounts of inundation areas to forecast and prevent from flood damage by using rainfall-runoff model. In this study, a case study method is adopted to show inundation by using rainfall-runoff model, HEC-GeoRAS and Arcview. It is hoped that, this study would be conducive to professionals and organizations working in the field of disaster management.

• Journal of Korean Society of Forest Science
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• v.104 no.3
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• pp.403-410
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• 2015

This study was conducted to analyze the forest environmental characteristics on a total of 20 forest environmental factors affecting the debris flow against 272 sites of risk areas. In the case of environmental factors, it showed the high risk of debris flow under the following conditions such as soil depth of less than 30cm, west slope, altitude of 200~300 m, mountain average slope of $25{\sim}30^{\circ}$, sandy loam, igneous rocks, and composite slope. Among the rainfall factors, 50~100 mm of maximum hourly rain fall and 300 mm of maximum rain fall per day have been shown the high risk of debris flow. Furthermore, the high risk of debris flow was related to the river-bed average slope of $10{\sim}20^{\circ}$, the river-bed average width of >10 m, the small amount of debris in river-bed (less than 20% of river-bed structure), the drainage density of >$1km/km^2$, the 40~60% of area with more than $20^{\circ}$ slope, and the 40~60% of areas with risk grade 2 of landslide. In addition, forest environmental factors including the driftwood, soil erosion control structures, age-class 3, crown density (density), and mixed forest were important factors causing the high risk of debris flow.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5B
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• pp.475-481
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• 2011

The TMDL standard flow as applying watershed management regime uses the average low flow of past 10 years. Moreover, the TMDL implementation assessment has been enforced through management of pollutant load satisfied objective water quality. Even though the present allocation and management through averaged low flow are still convenient, they are not enough to solve ultimate goals of watershed management to keep up recovery of water body. To maintain the same water quality concentration, the standard flow is required to consider total discharge in management plan which helps to keep healthy ecosystem. In view of this, it would be possible to approach reasonable assessment by reflecting variably changeable discharge from precipitation-streamflow relation and the TMDL standard establishment considering artificial regulated flow. Therefore, this study attempts to develop the TMDL method using Load Duration Curve (LDC) and Streamflow-Load Rating Curve (QLRC) considering total discharge and finds drawbacks with solutions as applying on Nakdong river TMDL unit watershed. Finally, this research evaluates possibility of application on pollutant load allocating and implementation assessment in Korea.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.1
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• pp.43-51
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• 2012

Due to the increasing demand to utilize water fronts and water resource effectively, a multi-dimensional model that provides detailed hydraulic characteristics is required in order to improve the decision making process. An EFDC model is a kind of multi-dimension model, and it requires detailed 3D (3-dimensional) terrain in order to simulate the hydraulic characteristics of stream flow. In the case of 3D terrain creation, especially river reaches, measurement resolution and spatial interpolation methods affect the detailed 3D topography which uses input data for EFDC simulation. Such results make hydraulic characteristics to be varied. This study aims to examine EFDC simulation results depending on the 3D topographies derived by separate measurement resolution and spatial interpolation methods. The study area is at the confluence of the Nakdong and Kuemho Rivers and the event rain implemented was Typhoon Ewiniar in 2006. As a result, in the case of the area-elevation curve, the difference by means of the interpolation methods was significant when applying the same measurement resolution, except at 160m resolution. Furthermore, when the measurement resolution was 80m or above, the difference in a cross-section was occurred. Meanwhile, the water level changes between interpolation methods were insignificant by the measurement resolution except when the Kriging method was used for the 160m measurement data. Velocity changes emerged according to the interpolation methods when measurement resolution was 80m or above and the Kriging method resulted in a velocity that had a considerable gap in relation to the results from other methods at a measurement resolution of 160m.

• Journal of Korea Water Resources Association
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• v.51 no.6
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• pp.481-490
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• 2018

Recently, the spatiotemporal patterns of flood disasters have become more complex and unpredictable due to climate change. Flood hazard map including information on flood risk level has been widely used as an unstructured measure against flooding damages. In order to product a high-precision flood hazard map by combination of hydrologic and hydraulic modeling, huge digital information such as topography, geology, climate, landuse and various database related to social economic are required. However, in some areas, especially in developing countries, flood hazard mapping is difficult or impossible and its accuracy is insufficient because such data is lacking or inaccessible. Therefore, this study suggests a method to delineate large scale flood-prone area based on topographic factors produced by linear binary classifier and ROC (Receiver Operation Characteristics) using globally-available geographic data such as ASTER or SRTM. We applied the proposed methodology to five different countries: North Korea Bangladesh, Indonesia, Thailand and Myanmar. The results show that model performances on flood area detection ranges from 38% (Bangladesh) to 78% (Thailand). The flood-prone area detection based on the topographical factors has a great advantage in order to easily distinguish the large-scale inundation-potent area using only digital elevation model (DEM) for ungauged watersheds.

• Journal of Korea Water Resources Association
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• v.49 no.1
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• pp.19-28
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• 2016

The objective of this study is the generation of the gridded flash flood index using the gridded hydrologic components of TOPLATS land surface model and statistic flash flood index model. The accuracy of this method is also examined in this study. The study area is the national capital region of Korea, and 38 flash flood damages had occurred from 2009 to 2012. The spatio-temporal resolutions of land surface model are 1 h and 1 km, respectively. The gridded meteorological data are generated using the inverse distance weight method with automatic weather stations (AWSs) of Korea Meteorological Administration (KMA). The hydrological components (e.g., surface runoff, soil water contents, and water table depth) of cells corresponding to the positions of 38 flood damages reasonably respond to the cell based hourly rainfalls. Under the total rainfall condition, the gridded flash flood index shows 71% to 87% from 4 h to 6 h in the lead time based on the rescue request time and 42% to 52% of accuracy at 0 h which means that the time period of the lead time is in a limited rescue request time. From these results, it is known that the gridded flash flood index using the cell based hydrological components from land surface model and the statistic flash flood index model have a capability to predict flash flood in the mountainous area.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.135-135
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• 2011

지구온난화와 이상기후에 따라 최근 우리나라를 둘러싼 기후패턴의 변화가 가속화되고 있으며 한반도는 장마기간이 소강상태를 보이는 반면, 장마 후 국지성 집중호우가 증가하고 태풍이 내습하는 현상이 빈번해짐으로써 홍수에 대한 위험과 피해규모도 증가하고 있다. 특히 도시지역에서는 강우규모가 배수시스템의 용량을 초과하거나, 하천수위 상승으로 관로 내에 역류가 발생하는 등 우수 배제 기능을 제대로 수행하지 못할 경우 발생하는 지표침수로 인해 심각한 인명 및 재산피해가 발생하고 있다. 실제로 현재 홍수해석 및 홍수위험지도 작성시 내수시스템을 반영하지 않아 침수면적 및 범위의 오차가 존재하며 홍수위험지도 작성시 내수범람과 외수범람을 따로 고려하는 문제점이 있다. 따라서 도시 침수 해석시 내수시스템을 반영한 정확한 침수심 및 침수면적계산뿐만 아니라 이상기후에 대비한 복합적 요인으로 인한 침수해석이 필요하다. 따라서 본 연구에서는 하천해석을 위해 1차원 하천 해석 모형인 FLDWAV모형을 적용하고 가상의 제방 파제 시나리오를 통하여 외수범람 영향을 구하였으며, 배수시스템의 SWMM모형과 제내지에서 내수와 외수범람의 영향을 고려한 DEM기반의 2차원 범람해석을 연계한 Dual-Drainage모형에 대하여 외수범람 영향에 따른 흐름의 양상, 침수심, 침수위 등을 분석하였다. 개발한 모형에 대한 적용성을 검토하기 위하여 대구 신암5동 유역을 선정하였고 대상유역의 수치지도를 활용하여 정형 격자 20m 크기로 지형자료를 구성하였으며, 건물의 영향도 고려하기 위해 DEM에 건물자료를 합성하였다. 침수해석 결과 내수시스템의 영향을 고려하지 않을 때가 고려하였을 때 보다 Node(맨홀)에서의 재유입의 영향으로 인하여 최대 침수심이 더 높게 나왔으며 침수면적도 넓게 나타나는 것을 확인하였고, 기존의 홍수위험지도 작성시 외수침수와 내수침수를 구분하여 해석하였던 것을 본 연구에서 통합하여 외수범람의 영향을 고려한 통합침수해석을 실시하여 내수에서 발생할 수 있는 유출량과 내수시스템의 월류량 등에 대한 고려가 없는 외수침수만 해석시 보다 최대침수심이 더 높게 나타났으며 침수면적 또한 넓게 나타남을 알 수 있었다. 본 연구를 통해서 도시홍수, 돌발홍수 등의 발생시 정확한 도시 침수 해석이 가능하며 도시침수구역에 대한 적절한 예 경보 및 피난대책 수립에 활용될 수 있을 것으로 사료된다. 또한 국내의 홍수위험지도나 도시 침수해석과 연계하여 선행시간을 확보한 정확도 높은 홍수정보시스템 구축에 크게 기여할 것으로 판단된다.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.4
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• pp.122-131
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• 2007

This study estimates how soil loss in a basin has been occurred according to the change of land cover, and analyzes which type of land cover has the largest soil loss by classifying the land-cover type into each area and a whole basin. Musimcheon, the second branch stream of GeumGang, is chosen as a research area. The result of analysis shows that the average soil loss occurs most largely in a crop land and a paddy field. The yearly soil loss of watershed estimates approximately 14,000 ton/yr in case of using 100-year-frequency rainfall data. A forest area, which takes the largest area in watershed, shows the soil loss occurs approximately 1,000ton/yr. A crop field shows that soil loss increased most largely 4,900 ton/yr (34.6%) in 1985 to 8,100 ton/yr (56.1%) in 2000. The change of land cover in a crop land increased 8% to 14%, and this change influences on the increase of soil loss. As a result of analyzing the area over $200ton/km^2/yr$, the soil loss in a crop field accounts for 74% to 96%.

• Journal of Environmental Impact Assessment
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• v.20 no.5
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• pp.651-661
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• 2011

The purpose of this study is to estimate the characteristics and pollutant loadings of non-point pollutants that flowed in the streams on precipitation for pollutant loading reduction of Hwa-sung lake inflow streams. Although it has been made an effort to improve the water quality of Hwa-sung basin through the strategies for the preservation of water quality, it is shown that the water quality is not greatly improved. Because it has been industrialized and urbanized near Hwa-sung basin so that it is difficult to reduce the water pollution due to the increase in pollutant loadings of point and non-point sources. In this study, it is investigated the outflow characteristics of non-point pollutants that discharged with storm runoff and estimated the effect of runoff on Hwa-sung basin. The final goal of this study is to utilize the basic information for proper management and strategies of non-point sources on Hwa-sung basin. At the result of inflow streams, Ja-an stream that has the greatest pollutant loadings on precipitation is strongly influenced on the water quantity of Hwa-sung basin. On the other hand, it is shown that Nam-yang stream is strongly influenced on the SS concentration of Hwasung basin among them. Also, all streams; Nam-yang, Ja-ahn, Ah-eun stream; has the degree of slope more than or near 1 in the correlation results so that they have strong pollutant loading impact and the concentration of SS is the highest among other pollutants. So, specific studies on initial rain phenomena are more necessary to manage the pollutants economically. Also, the proper control of SS concentration is required to manage the effluent pollutants effectively on precipitation. So, it is necessary to consider the strategies for non-point pollutants as well as point pollutants when the new management is imposed to reduce the pollutant load for improvement of Hwa-sung basin.