• Journal of Korean Society of Water and Wastewater
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• v.20 no.3
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• pp.347-355
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• 2006

Anyang Stream including its main branch is the biggest branch stream of Han River in Korea. The geological and geomorphological characteristics were investigated to the affected area of Anyang Stream, in which rainfall characteristic was analyzed. The water quality surveyed that the analysis of water pollution used to biotic index and biological water pollution. The rainfall pattern in this area was like to that of typical Korea, but the rate of trigger and runoff during summer season(June~August) is more higher than mean of Korea. Before 2003, a dried stream is severe status, which was due to abundant runoff, but this status are improved. After 1997, water quality of stream is recovering status such as water pollution of stream steeply decreased. Especially after 2003, this trend is more quickly improved. Although, owing to the increasing of a T-N and SS at upstream wastewater were due to bad collection of industrial factories, livestock's and mans living, the water quality worsted at upstream. Water quality in total section of main stream was severely contaminated that water-quality limit is 5 with polysaprobic by water self-purification. That of main branch was 1~3limits with ${\alpha}$- and ${\beta}$-mesosaprobic in Anyang city area, But water quality in all area about another branch of Anyang stream except Anyang city area was almost under of 3 grades. Though trying of Anyang city for recover movement(completion of 2nd Sewage Treatment Plant and Water supply pipe system) on Anyang stream, water pollution states of upper branch in Anyang stream was not better than its of 2002 because it may be difference of control area on other cities.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.101-113
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• 2007

A landslide was occurred due to soil cutting for construction to expand the Donghae express highway in Dong-hae-City, Korea. The total area of the landslide was about $9,550m^2$ with 100 m of width and 87m of height. The landslide was occurred due to the internal factor of the unstable geological structure including the clay layer and the external factor of continuous heavy rainfalls. As the result of field instrumentation during the landslide, the horizontal displacement of the slope ground increases with increasing the accumulated rainfall by continuous rainfall during the rainy season. Also, the depth of sliding failure was decided by the horizontal displacement distribution during landslide occurrence. It makes sure that the horizontal displacement starts from the depth of sliding failure and the depth of sliding failure matches well with the location of the clay layer. As the slope stability analysis using Bishop's Simplified Method at the landslide area, the safety factor of slope during the rainy season was 0.53. This safety factor of slope was enough to trigger the landslide at this area. The depth of sliding failure obtained by analytical method matches well with the depth of the clay layer.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1205-1214
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• 2021

Precipitation is one of a major causes of landslides by rising of pore water pressure, which leads to fluctuations of soil strength and stress. For this reason, precipitation is the most frequently used to determine the landslide thresholds. However, using only precipitation has limitations in predicting and estimating slope stability quantitatively for reducing false alarm events. On the other hand, Soil Moisture (SM) has been used for calculating slope stability in many studies since it is directly related to pore water pressure than precipitation. Therefore, this study attempted to evaluate the appropriateness of applying soil moisture in determining the landslide threshold. First, the reactivity of soil saturation level to precipitation was identified through time-series analysis. The precipitation threshold was calculated using daily precipitation (P_daily) and the Antecedent Precipitation Index (API), and the hydrological threshold was calculated using daily precipitation and soil saturation level. Using a contingency table, these two thresholds were assessed qualitatively. In results, compared to P_daily only threshold, Goesan showed an improvement of 75% (P_daily + API) and 42% (P_daily + SM) and Changsu showed an improvement of 33% (P_daily + API) and 44% (P_daily + SM), respectively. Both API and SM effectively enhanced the Critical Success Index (CSI) and reduced the False Alarm Rate (FAR). In the future, studies such as calculating rainfall intensity required to cause/trigger landslides through soil saturation level or estimating rainfall resistance according to the soil saturation level are expected to contribute to improving landslide prediction accuracy.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.816-820
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• 2005

본 연구에서는 해안 도시 하천의 범람으로 인한 홍수 재해 발생시 예상될 수 있는 피해에 대해 적절한 홍수예경보 및 피난대책을 수립하고자 대표적인 해안 도시 하천의 특성을 가지는 부산시 온천천 유역을 대상으로 수치지도에서 각종 지형자료를 추출하였고 수문 GIS 자료를 구축하였다. 그리고, 하천 수리 분석을 위한 한계유출량 산정을 위해 HEC-RAS 모형을 이용 조위의 영향을 고려하여 홍수위 및 한계유출량을 산정하였고 수문 분석을 위한 도시 돌발 홍수 기준 우량 산정을 위해 PCSWMM 2002를 이용하여 기준 우량을 산정하였다. 전형적인 해안 도시 지역 유역 특성을 나타내는 부산시 온천천 유역에 대한 경보발령 기준을 설정하기 위하여 선정지점 세 곳의 한계수심 $H_{c1},\;H_{c2},\;H_{c3},\;H_{c4}$가 발생할 수 있는 강우량(위험 홍수량을 유발하는 위험 강우량(Trigger Rainfall))을 산정하였고 PCSWMM을 이용한 모형화 기법으로 해안 도시 돌발 홍수 기준 우량을 산정하였다. 산정 결과 온천천 유역의 홍수예경보 시스템과 이에 따른 홍수예경보 발령흐름도, 운영체계가 결정되어 해안 도시 돌발 홍수예경보 방안이 구축되었다. 해안 도시의 홍수 관리는 도시 우수 시스템, 하천, 해안 특성이 복합된 문제이다. 현재 해안 도시 지역의 홍수예경보 시스템 구축 실적이 전무한 실정임을 볼 때 현실적으로 실용화 할 수 있는 시스템 개발을 해내는 것이 무엇보다도 시급하고 중요한 문제이다. 앞으로 더욱 심도있게 연구하여 주요 하천에 대한 홍수예경보 시스템 구축이 절실히 요구된다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.2
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• pp.59-66
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• 2018

This study examined the correlation among topography, forest type, soil and geology in Inje area where landslides occurred during heavy rainfall from July 11 to July 18, 2006 to assess the landslide susceptibility. In order to assess the susceptibility of future landslides, landslides occurred in Inje area were classified into slide type and flow type, and slope angle, aspect, curvature, ridge and valley were extracted from the area. The landslide susceptibility was assessed by applying diameter class, age class, density, and forest type to Bayesianbased LR (Logistic Regression) model and WOE (Weight of Evidence) model, and the fitness of modeling was verified by predict rate curve. As the results of susceptibility assessment, using all landslides without no distintion, it was found that 75% of the LR model and 73% of the WOE model were fit in terms of the top 20% of the landslides. According to slide type and flow type in the top 20% of the landslides, it was found that 71% of the LR model and 69% of the WOE model were fit in terms of the slide type. Whereas, it was found that 86% of the LR model and 82% of the WOE model were fit in terms of the flow type. That is, the results of the LR model showed higher fitness than the results of the WOE model, and the fitness of the flow type was higher than that of the slide type. Consequently, it suggests that it is reasonable to assess and verify the landslide susceptibility according to the types of landslides.