• Title/Summary/Keyword: Flood variation

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Analysis of Hydraulic Characteristics of Flood Plain Using Two-Dimensional Unsteady Model (2차원 부정류 모형을 이용한 둔치의 수리특성 분석)

  • Ku, Young Hun;Song, Chang Geun;Kim, Young Do;Seo, Il Wo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.3
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    • pp.997-1005
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    • 2013
  • Since the cross-sectional shape of the Nakdong river is compound type, the water stage rises up to the top of the flood plane, as the flow discharge increases during the extreme rain storm in summer. The recent increase of rainfall intensity and flood frequency results in the immersions of parks and hydrophilic facilities located in the flood plain. Therefore it is necessary to analyze the hydraulic characteristics evolved by the extreme rain storm in the flood plain. The study reach ranging from the Gangjeong Goryeong Weir and the Dalseong Weir, where several hydraulic facilities are located along the channel, was selected and numerical simulations were conducted for 42 hours including the peak flood of the typhoon Sanba. The 2-D transient model, FaSTMECH was employed and the accuracy of the model was assessed by comparing the water level between the simulation results and the measured ones at a gauging station. It showed a high correlation with $R^2$ of 0.990, AME of 0.195, and RMSE of 0.252. In addition, the inundation time, the inundation depth, the inundation velocity, and the shear stress variation in the flood plain facilities were analyzed.

Runoff Characteristics Analysis for Interior Drainage Systems in Urban Basin -Application of SWMM- (도시유역의 내수배제시스템 설계를 위한 유출특성분석 -SWMM의 적용-)

  • Choi, Yun-Young;Lee, Yeong-Hwa
    • Journal of Environmental Science International
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    • v.9 no.3
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    • pp.193-199
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    • 2000
  • This study is carried out the analysis of the runoff characteristics for the design of the interior drainage systems by SWMM in urbanization basin. The basin analyzed in this study is Bumuh-chun basin which is located in Susung-gu of Taegu city. Huff method is used for rainfall distribution analysis. The optimal rainfall duration in Bumuh-chun basin is analyzed as about 90 minutes decided from comparison of arrival time and critical duration. Flood flow variation pattern is proposed through the comparison of the results of peak flow and peak time analyzed by SWMM about pre-urbanization and post-urbanization of Bumuh-chun basin. It is known that the variation of arrival time caused by the rapid increase of pavement rate in the upper area shows about 20∼25 minutes faster than pre- urbanization. Therefore, the management of surface water for design of water supply and drainage, and channel alteration has to considered the variation of geological factors according to urbanization.

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Derivation of Optimal Design Flood by L-Moments (L-모멘트법에 의한 적정 설계홍수량의 유도)

  • 이순혁;박명근;맹승진;정연수;김동주;류경식
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 1998.10a
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    • pp.318-324
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    • 1998
  • This study was conducted to derive optimal design floods by Generalized Extreme-value(GEV) distribution for the annual maximum series at ten watersheds along Han, Nagdong, Geum, Yeongsan and Seomjin river systems. Adequacy for the analysis of flood data used in this study was established by the tests of Independence, Homogeneity, detection of Outliers. L-coefficient of variation, L-skewness and L-kurtosis were calculated by L-moment ratio respectively. Parameters were estimated by the Methods of Moments and L-Moments. Design floods obtained by Methods of Moments and L-Moments using different methods for plotting positions in GEV distribution were compared by the relative mean and relative absolute error. It was found that design floods derived by the method of L-moments using weibull plotting position formula in GEV distribution are much closer to those of the observed data in comparison with those obtained by method of moments using different formulas for plotting positions in view of relative mean and relative absolute error.

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Analysis on the sediment sluicing efficiency by variation of operation water surface elevation at flood season (홍수기 운영수위 변화에 따른 배사 효율 분석)

  • Jeong, Anchul;Kim, Seongwon;Kim, Minseok;Jung, Kwansue
    • Journal of Korea Water Resources Association
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    • v.49 no.12
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    • pp.971-980
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    • 2016
  • In general, efficient operation of sediment sluicing is important in economical aspect. In this study, the efficiency of sediment sluicing by various operation at water surface elevation on multi-functional weirs were analyzed using Nays2DH, and we focused on the Dalsung weir at Nakdong river. The results of this study shows that, the same number of flushing channels and water gates were developed due to sediment sluicing, and sediment deposition occurred in upstream region of flushing channels. Also, the sediment sluicing efficiency increased by approximately 4.6% and sedimentation decreased by approximately 4.5% at EL. 14.5 m for operations on water surface elevation exceeding EL. 14.0 m. The mitigation of reservoir sedimentation and extension of maintenance dredging period are possible if the variation of sediment sluicing efficiency in various operation at water surface elevation during flood season are considered.

Numerical Analysis of Dam-break Waves in an L-shaped Channel with a Movable Bed (L자형 이동상수로에서 댐 붕괴파의 수치해석)

  • Kim, Dae-Geun;Hwang, Gun
    • Journal of Korea Water Resources Association
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    • v.45 no.3
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    • pp.291-300
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    • 2012
  • We conducted a three-dimensional numerical simulation by using the FLOW-3D, with RANS as the governing equation, in an effort to track the dam-break wave.immediately after a dam break.in areas surrounding where the dam break took place as well as the bed change caused by the dam-break wave. In particular, we computed the bed change in the movable bed and compared the variation in flood wave induced by the bed change with our analysis results in the fixed bed. The analysis results can be summarized as follows: First, the analysis results on the flood wave in the L-shaped channel and on the flood wave and bed change in the movable-bed channel successfully reproduce the findings of the hydraulic experiment. Second, the concentration of suspended sediment is the highest in the front of the flood wave, and the greatest bed change is observed in the direct downstream of the dam where the water flow changes tremendously. Generated in the upstream of the channel, suspended sediment results in erosion and sedimentation alternately in the downstream region. With the arrival of the flood wave, erosion initially prove predominant in the inner side of the L-shaped bend, but over time, it tends to move gradually toward the outer side of the bend. Third, the flood wave in the L-shaped channel with a movable bed propagates at a slower pace than that in the fixed bed due to the erosion and sedimentation of the bed, leading to a remarkable increase in flood water level.

Numerical Analysis for Bed Changes at the Meandering Stream due to a Short Term Flood Event (단기 홍수사상으로 인한 사행하천의 하상변동 수치모의 분석)

  • Ji, Un;Jang, Eun Kyung;Lee, Chan Joo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.35 no.6
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    • pp.1229-1236
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    • 2015
  • In this study, flow characteristics and bed changes during a short term flood event were analyzed using the two-dimensional CCHE2D model for a meandering sand-bed river, the Naesung Stream. Flow and bed change simulation was carried along the three sub-reaches with sinuosity of 1.2, 1.6 and 2.2 for the 6-day flood event occurring in June 2011. The simulation results indicated that velocity variation due to flow concentration was larger along the sub-reach with the sinuosity less than 1.5 and bed erosion at the outside of the bend was increased by time. In the sub-reach with the sinuosity less than 1.5, the maximum flood discharge produced the maximum flow velocity over 1.6 m/s to 2 m/s locally.

A Study on Numerical Simulation of Flood Inundation in a Coastal Urban Areas: Application to Gohyun River in Geoje City, Kyungnam Province (해안도시지역 홍수범람모의에 관한 연구: 경상남도 거제시 고현천 적용사례)

  • Jeong, Woochang
    • Journal of Korea Water Resources Association
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    • v.45 no.11
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    • pp.1093-1105
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    • 2012
  • In this study, the simulations and analyses of flood flow due to a river inundation in a coastal urban area are carried out using a two-dimensional finite volume model with well-balanced HLLC scheme. The target area is a coastal urban area around Gohyun river which is located at Geoje city in Kyungnam province and was extremely damaged due to the heavy rainfall during the period of the typhoon "Maemi" in September 2003. For the purpose of the verification of the numerical model applied in this study, the simulated results are compared and analyzed with the inundation traces. In addition, the flood flow in an urban area is simulated and analyzed according to the scenarios of inflow variation due to the increase and decrease of the intensity of the heavy rainfall, which.

The Development and Evaluation of a Simple Semi-Quantitative Food Frequency Questionnaire Using the Contribution of Specific Foods to Absolute Intake and Between-Person Variation of Nutrient Consumption (영양소 섭취의 주요급원식품과 주요변이식품들을 이용한 간소화된 반정량 빈도 조사 도구의 개발 및 평가)

  • Kim, Mi-Yang;Suh, Il;Nam, Chung-Mo;Yoon, Jee-Young;Shim, Jee-Seon;Oh, Kyung-Won
    • Journal of Nutrition and Health
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    • v.35 no.2
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    • pp.250-262
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    • 2002
  • This study was conducted to develop a simple flood frequency questionnaire (FFQ) based on the results of contributions of specific floods to absolute intake and between-person variance in nutrients using semi-quantitative FFQ with 93 flood items. The subjects were 554 healthy adults for development of a simple FFQ, and 37 students for a validation test of a developed simple FFQ. The contribution of specific floods to 80% absolute nutrient intake was measured by assessing their percentage in total consumption of a nutrient. To assess the contributions of floods to the between-person variance in the intake of each specific nutrient, stepwise multiple regressions were performed. The number of floods necessary to account for the respective 80% of absolute intake was 11-36, depending on the nutrient, while flower floods (5-16 floods) were required for the corresponding percentage of between-person variation for all nutrients. Important floods for between-person variance include Tangsuyuk (pork) and snacks for energy and fat, fish for protein and polyunsaturated fatty acids (PUFA) and snacks for carbohydrates. Spearman correlation coefficients between 93-itemed FFQ and 63-itemed FFQ ranged from 0.91 for vitamin A to 0.99 for fat in the population data used in developing a simple FFQ. Also, the correlation coefficients between the two FFQs were 0.82-7.92 in the population for the validation test. This study suggests that useful information on dietary intake could be obtained using a simple semi-quantitative FFQ in a large-scale dietary survey in Korea.

Characteristics of Bed Profile Fluctuation According to Before & After Removal of the Sediment Protection Weir using HEC-6 model (HEC-6모형을 이용한 방사보 철거 전후에 따른 하상변동 특성)

  • Ahn, Seung-Seop;Lee, Soo-Sik;Choi, Yun-Young;Lee, Jeung-Seok
    • Journal of the Korean Society of Hazard Mitigation
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    • v.1 no.3 s.3
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    • pp.93-102
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    • 2001
  • In this study, the characteristics of river bed profile fluctuation are become possible to be used effectively in future estimation of Taehwa river general development plan through analysis and examination according to the effects of sediment protection weir located in the area of the estuary of Taehwa river's main channel using HEC-6 model. The flow conditions needed in analysis of the characteristics of river bed profile fluctuation refer the conditions of flow which secures 95 days in a year, flood flow, and design flood examined in the estimation of Taehwa river maintenance basic plan. First, in analysis result of river bed variation range, there is no significant variation in upstream section from Samho-gyo while there are the more active erosion and sedimentation as the more flow in downstream from Samho-gyo. Next, from the result of the capacity of sediment transfer, it is analyzed that sediment transfer capacity in the area of estuary of Taehwa river has no significant difference in before and after removal of the sediment protection weir when design flood flows while it is estimated that the more flow, the bigger sediment transfer capacity. Therefore, it is thought that the installation of a suitable hydraulic structure at the lowest point of Dong-chun tributary joins from the downstream of Taehwa river can be a good device to reduce the accumulation of sediments at the lowest point of Taehwa river considering the reduction plan of sediment inflow caused by removal of the sediment protection weir.

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Movement of Sand around Revetment under Water Pressure Variation

  • HoWoongShon
    • Journal of the Korean Geophysical Society
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    • v.6 no.4
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    • pp.221-230
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    • 2003
  • Many hydraulic structures are damaged by under flood flow and storm waves year after year. Many cases of dike and breakwater failure are caused by the suck out of sand from behind the revetment. This type of failure will be in close relation to the dynamic behavior of sand bed around the revetment. In this paper, from this point of view we investigated the basic characteristics of such sand movement by small model tests and tried to explanation the hydro- and soil mechanical mechanism of this phenomenon theoretically.

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