• Journal of the Korean Society of Safety
• /
• v.27 no.6
• /
• pp.172-177
• /
• 2012

In areas around Deoksan Li and Deokjeon Li, Inje Eup, Inje Gun, located between $38^{\circ}2^{\prime}55^{{\prime}{\prime}}N$ and $38^{\circ}5^{\prime}50^{{\prime}{\prime}}N$ in latitude and $128^{\circ}11^{\prime}20^{{\prime}{\prime}}E$ and $128^{\circ}18^{\prime}20^{{\prime}{\prime}}E$ in longitude, large-sized avalanche disasters occurred due to Typhoon Ewiniar in 2006. As a result, 29 people were dead or missing, along with a total of 37.25 billion won of financial loss(Gangwon Province, 2006). To evaluate such landslide and debris flow risk areas and their vulnerability, this study applied a technique called 'Weight of Evidence' based on GIS. Especially based on the overlay analysis of aerial images before the occurrence of landslides and debris flows in 2005 and after 2006, this study extracted 475 damage-occurrence areas in a shape of point, and established a DB by using such factors as topography, hydrologic, soil and forest physiognomy through GIS. For the prediction diagram of debris flow and landslide risk areas, this study calculated W+ and W-, the weighted values of each factor of Weight Evidence, while overlaying the weighted values of factors. Besides, the diagram showed about 76% in prediction accuracy, and it was also found to have a relatively high correlationship with the areas where such natural disasters actually occurred.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.11 no.1
• /
• pp.99-108
• /
• 1991

Rapid changes of urban hydrologic events need new management operation rule of detention reservoir which is essential outflow control system in urban area. Therefore, this study is to develop the outflow management method of Seoul city considering the Han river flood characteristics, to analyze the inundation of detention reservoir according to variation of design storm patterns, and to examine the safety of gate due to design flood water level. From this study, new operation rule is presented. The design storm patterns are determined by instantaneous intensity method and Huff's quartile method. And the inflow hydrograph of detention reservoir is obtained by applying ILLUDAS model and RRL method. The operation rule of existing drainage pump is designed to have linear relation between storage and pumping discharge. But in this study, it is effective for preventing inundation when the operation rule of drainage pump have Gaussian function which is combined the storage of detention reservoir with its inflow according to increasing or decreasing of inflow hydrograph.

• Journal of Wetlands Research
• /
• v.13 no.1
• /
• pp.53-66
• /
• 2011

We estimated the expected flood damage considering uncertainty which is involved in hydrologic processes and data. Actually, this uncertainty represents a freeboard or safety factor in the design of hydraulic structures. The uncertainty was analyzed using Bootstrap method, and SIR algorithm then the frequency based rainfalls were estimated for each method of uncertainty analysis. Also the benefits for each uncertainty analysis were estimated using 'multi-dimensional flood damage analysis(MD-FDA). As a result, the expected flood damage with SIR algorithm was 1.22 times of present status and Boostrap 0.92 times. However when we used SIR algorithm, the likelihood function should be selected with caution for the estimation of the expected flood damage.

• Journal of Korea Water Resources Association
• /
• v.31 no.1
• /
• pp.105-113
• /
• 1998

Reservoir operation during flood period can be divided into two parts: One is for an operating policy during flood period to consider water conservation and flood control, and the other is for flood time on a random water level at flood forecasting, This study is concerned with reservoir operation and discusses general reservoir operation at flood time. Flood control has problems such as the uncertainty of hydrologic models. technical limitations and some constraints. Therefore, we may prepare the quantitative flood control methods based on the assured flood control storage for reservoir operation. Transformed Reservoir Flood(TRF) Reservoir Operation Method(ROM) is a procedure which determines the adequate releases with considering dam safety for flood inflows over non-damaging discharge. Based on the TRF ROM which was explained in our published paper. the study discusses the TRF ROM with additional investigations and the general reservoir operation rules at flood time.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.62 no.6
• /
• pp.1-9
• /
• 2020

Reservoir storage and water level information is essential for accurate drought monitoring and prediction. In particular, the agricultural drought has increased the risk of agricultural water shortages due to regional bias in reservoirs and water supply facilities, which are major water supply facilities for agricultural water. Therefore, it is important to evaluate the available water capacity of the reservoir, and it is necessary to determine the water surface area and water capacity. Remote sensing provides images of temporal water storage and level variations, and a combination of both measurement techniques can indicate a change in water volume. In areas of ungauged water volume, satellite remote sensing image acts as a powerful tool to measure changes in surface water level. The purpose of this study is to estimate of reservoir storage and level variations using satellite remote sensing image combined with hydrological statistical data and the Normalized Difference Water Index (NDWI). Water surface areas were estimated using the Sentinel-2 satellite images in Seosan, Chungcheongnam-do from 2016 to 2018. The remote sensing-based reservoir storage estimation algorithm from this study is general and transferable to applications for lakes and reservoirs. The data set can be used for improving the representation of water resources management for incorporating lakes into weather forecasting models and climate models, and hydrologic processes.

• Journal of Korea Water Resources Association
• /
• v.42 no.7
• /
• pp.547-558
• /
• 2009

General reliability assessment of levees embankment is performed with safety factors for rainfall characteristics and hydrologic and hydraulic parameters, based on the results of deterministic analysis. The safety factors are widely employed in the field of engineering handling model parameters and the diversity of material properties, but cannot explain every natural phenomenon. Uncertainty of flood analysis and related parameters by introducing stochastic method rather than deterministic scheme will be required to deal with extreme weather and unprecedented flood due to recent climate change. As a consequence, stochastic-method-based measures considering parameter uncertainty and related factors are being established. In this study, a variety of dimensionless cumulative rainfall curve for typhoon and monsoon season of July to September with generation method of stochastic temporal variation is generated by introducing Monte Carlo method and applied to the risk assessment of levee embankment using reliability index. The result of this study reflecting temporal and regional characteristics of a rainfall can be used for the establishment of flood defence measures, hydraulic structure design and analysis on a watershed.

• Journal of Korea Water Resources Association
• /
• v.48 no.3
• /
• pp.149-158
• /
• 2015

It is well known that emergency outlet works have to be provided for the safety of dams. However, concept of emergency outlet works did not applied for the design of the most dams in Korea. Korean design standard for low-level outlet works does not provide enough design criteria which could be used in design of emergency outlet works. In this research, as-built status and hydraulic design criteria of outlet works, such as drawdown rate or hydraulic pressure due to the impounded water depth, were examined. Another relationship between drawdown rate and the dam slope stability was also examined with SEEP model. It was found that 25% reduction of impounded water depth decreases the pressure forces about 50%. Therefore, outlet works should be designed to drawdown properly at the beginning of the emergency. Seepage analysis of dam bodies showed that most of Korean dams could safely stand for 1m/day drawdown rate. Higher drawdown rate could result high discharge so the drawdown rate must be related with the flood risk of downstream. Finally, multi-stage design was recommended that faster discharge for the initial 25% of water depth in 7-10 days than the rest of it in 1-2 months.

• Journal of Korea Water Resources Association
• /
• v.49 no.12
• /
• pp.1027-1034
• /
• 2016

One of the most important purpose of multi-purpose reservoir is storing a large amount of water for utilization in a dry season. However, multi-purpose reservoirs that were constructed according to the limited hydrologic information available at the time of construction may encounter problems such as decreased water inflow due to climate change and an inability to cope with a water shortage. To solve these problems, in 2015, the Ministry of Land, Infrastructure and Transport suggested a revised water supply standard in case of water shortage for reservoirs. However, the revised standard has not been sufficiently discussed to determine its effectiveness. In addition, multi-purpose reservoirs in South Korea have secured and stored water for emergencies, but there is currently no way to utilize the stored water. Determining how to utilize the stored water effectively may be a useful method for preparing drought. Therefore, this article discusses the revised water supply standard as it relates to a water shortage in reservoirs and a method of utilizing the water stored for emergencies in multi-purpose reservoirs. The options for utilizing the water storage were evaluated using a water shortage safety degree index, and the results showed that the options may slightly and limitedly increase the water supply capacity. However, the evaluation also showed that a complex application of two options may overcome the exisiting problem and to supply water more effectively.

• Journal of Korea Water Resources Association
• /
• v.46 no.10
• /
• pp.1029-1040
• /
• 2013

This study aims to develop a multivariate daily rainfall simulation model considering spatial coherence across watershed. The existing Hidden Markov Model (HMM) has been mainly applied to single site case so that the spatial coherences are not properly addressed. In this regard, HMM coupled with Chow-Liu Tree (CLT) that is designed to consider inter-dependences across rainfall networks was proposed. The proposed approach is applied to Han-River watershed where long-term and reliable hydrologic data is available, and a rigorous validation is finally conducted to verify the model's capability. It was found that the proposed model showed better performance in terms of reproducing daily rainfall statistics as well as seasonal rainfall statistics. Also, correlation matrix across stations for observation and simulation was compared and examined. It was confirmed that the spatial coherence was well reproduced via CLT-HMM model.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2010.05a
• /
• pp.377-382
• /
• 2010

국내에는 약 14,000개의 중 소규모의 저수지들이 있다. 최근에 이상기후로 인한 많은 강우가 발생하여 저수지들의 월류나 파이핑으로 인한 붕괴가 지속적으로 일어나고 있어 많은 인명 및 재산피해가 발생하고 있다. 특히 설계홍수량을 초과하는 월류로 인한 댐 붕괴 발생 시 피해규모가 크기 때문에 전국적으로 본포되어 있는 저수지들의 설계홍수량을 시급히 파악하여 저수지의 수문학적 안전성을 판단하고 설계홍수량이 작은 저수지의 경우 별도로 관리 할 수 있어야 한다. 하지만 기존에 저수지의 안전여부를 판단 할 수 있는 댐 붕괴 모의의 경우 많은 시간과 노력이 요구 되어 저수지의 안전여부를 보다 쉽고 빠르게 판단 할 수 있는 기준 마련이 시급히 필요하다. 본 연구에서는 보다 쉽고 빠르게 소규모저수지의 수문학적 안전성 평가를 할 수 있는 간편법에 대하여 연구 하였다. 연구 방법은 HEC-HMS을 이용한 댐 붕괴와 본 연구에서 제시한 간편법을 통하여 홍수량의 비교 검토 및 저수지의 수문학적 안전성을 평가를 하였다. HEC-HMS의 첨두홍수량은 빈도별 지속시간별 확률강우량을 이용하여 산정하였으며, 가능최대홍수량(PMF)은 실제호우전이법으로 산정한 가능최대강수량(PMP)을 이용하였다. 간편법의 첨두홍수량은 합리식과 통합형 강우강도식을 이용하여 산정하였고, 가능최대홍수량(PMF)은 Creager공식을 이용하여 산1)정하였다. 댐 붕괴의 경우 HEC-HMS에서는 댐 붕괴 모듈을 실행하여 모의를 하였고, 간편법의 댐 붕괴는 여수로의 한계 유출을 파악할 수 있는 위어공식을 이용하여 댐 붕괴 모의를 하였다. 마지막으로 산정된 첨두홍수량과 가능최대홍수량(PMF)을 작성된 수문학적 안전성 평가표에 기입하여 비교 분석하였다. 연구결과 HEC-HMS로 산정한 빈도별 첨두홍수량 가능최대홍수량(PMF)과 간편법으로 구한 빈도별 첨두 홍수량 가능최대홍수량(PMF)의 차이는 약 편차가 50%정도로 간편법으로 구한 첨두홍수량 가능최대홍수량(PMF)이 더 크게 산정되었다. 편차의 발생 이유는 본 연구에서 제시한 간편법의 경우 안전율을 고려한 경험공식을 사용하였기 때문이라고 판단되며, 간편법을 통한 소규모저수지의 수문학적 안전성 평가를 다른 대상지역의 소규모저수지에도 적용하여 보고 수문학적 평가방법이 올바르게 적용 될 수 있는지 확인이 필요하다고 판단된다.