• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2B
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• pp.147-154
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• 2011

Physical habitat assessment models based on Instream Flow Incremental Methodology have been developed as a decision making tool to estimate appropriate discharge for environmental flow and water use management. These models, however, require extensive knowledge on various academic disciplines, complicated input data, and empirical data. We propose a Simplified Habitat (SIMHAB) simulation model for the estimation of physical structure of fish habitat and environmental flow at the planning stage. SIMHAB is applied to a river system for which physical and ecological data are available, and its applicability is investigated. Simulated results appeared to be similar to field survey data and those of such models as PHABSIM and River2D. However, SIMHAB requires much less input data. As such, the proposed model, SIMHAB can easily be applicable to river restoration projects including designing of physical habitat, estimation of environmental flow, and water resource management.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.53-53
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• 2022

본 연구는 낙동강 상류에 위치한 안동댐 하류(4,565.7 km²)를 대상으로 1차원 물리적 서식처모형인 PHABSIM(Physical Habitat Simulation System)과 2차원 물리적 서식처 모형인 River2D를 이용하여 대표어종인 피라미에 대해 환경생태유량과 어류서식처 면적을 산정하였다. 두 모형의 구축을 위해 낙동강 하천기본계획보고서(2009)를 수집하여 하천단면과 수리학적 자료를 두 서식처모형에 적용하였다. 유속과 수위자료의 경우, 낙동강수문조사연보와 검보정된 HEC-RAS를 활용하여 갈수량 Q355(10.95 m³/sec)와 평수량 Q185(41.72 m³/sec)에서의 유속과 수위를 생성하여 적용하였다. 대표어종 선정을 위해 총 4회에 걸쳐 현장조사를 진행하였으며, 수집한 어종들에 대해 상대풍부도와 출현 개체수 분석결과 54.2%의 상대풍부도와 총 110개의 개체수를 나타낸 피라미(Z acco platypus)를 대표어종으로 선정하였다. 서식처 적합도 지수 HSI(Habitat Suitability Index)는 피라미 출현시기의 수심(Depth), 유속(Velocity) 그리고 하상재료(Substrate)를 조사하여 적립하였으며 수심은 0.4~0.6 m, 유속은 0.3~0.5 m/s, 하상재료는 모래(2.0 mm)~잔자갈(16.0 mm)일 때 HSI가 가장 적합한 것으로 분석되었다. PHABSIM을 이용하여 피라미에 대해 최적 환경생태유량 산정결과 20.0 m³/sec로 산정되었고, 모의한 30개 유량에 대해 평균 어류서식처 면적은31,905.3 m²/1,000m로 산정되었다. PHABSIM으로 산정된 환경생태유량과 River2D를 이용하여 하천유량이 Q355와 환경생태유량일 때의 공간분석을 실시하였다. Q355와 비교하여 환경생태유량일 때 유속과 수심 HSI에 대한 공간분포와 어류서식처 면적 또한 더 큰 것으로 분석되었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6B
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• pp.589-598
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• 2010

When the hydraulic structures, such as bridge and weir, are consecutively installed to a short section of a river with complicated cross section, analyzing the flow characteristics and the riverbed change modality of the river is very important. In the 250 m section of the Taehwa river near the Samho-bridge, which passes through Ulsan city, three bridges has been installed, and the tributary water is flowing into both up and downstream of the section. Due to these factors, when the flood occurs, the cross section of the river changes vastly by the water level change and scour. Even so, due to the fact that the Samho-bridge divides the section into two parts, the national river and the regional river, each part is being analyzed separately by the onedimensional model. In this study, the flow characteristics due to the bridge concentration and the tributary water inflow were jointly analyzed for both up and downstream by using the one-dimensional HEC-RAS model and the two-dimensional SMS model, such as RMA2. The riverbed change modality of the section was also investigated by using the SED2D model. The results showed that the water level difference between the HEC-RAS and RMA2 was 0.87 m when applied to the three consecutive bridges. The riverbed change simulation using SED2D showed that the maximum scour was 0.231 m and it occurred at the Samho-bridge, which located in the middle and has short pier distance. In conclusion, when planning the river maintenance for the regions with concentrated bridges or the sections with severe changes in cross-section and flow, estimating the flood elevation by two-dimensional model and establishing countermeasures for the scouring of the bridge are required. In addition, an integrated analysis on both the national river and the regional river is necessary.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.176-176
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• 2015

최근 대하천사업을 통하여 낙동강에 총 8개의 다기능보가 설치되었으며, 이러한 하천 내 수공 구조물은 하천에 서식하는 어류의 이동과 군집의 변화, 유전적 단절, 서식처 변화와 같은 다양한 문제점을 유발할 수 있으며, 특히 어류의 산란기에는 하천의 유로를 따라 상류로 이동하거나 하류로 이동하는 회유성 어류들에게는 심각한 문제를 야기한다. 이러한 다기능보의 상 하류의 단절로 인한 문제를 해결하기 위해 낙동강 8개의 다기능보에 자연형 및 인공형 어도가 설치되었으며, 이를 평가하기 위한 어도의 유인효율에 대한 연구가 중요하다. 어류는 최대 유속이 발생하는 지점인 유심선에서 소상하려는 특성을 보이는데, 어도의 입구부의 유속이 중요하게 작용한다. 어도 입구부의 유속분포 및 수심에 따라 유인효율은 다르게 나타날 수 있으며, 2차원 수리해석을 통해 WUA를 산정함으로써 어도의 유인효율을 평가할 수 있다. 본 연구에서는 2차원 흐름해석 모형인 River2D를 이용하여 어류의 소상이 중요한 산란기를 기준으로 강정고령보의 가동보 운영실적을 이용하여 수리해석을 실시하였으며, 연구결과를 바탕으로 자연형어도의 유인효율을 평가하였다.

• Journal of Korea Water Resources Association
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• v.51 no.10
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• pp.895-903
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• 2018

There are a large number of weirs installed in rivers of Korea, and these characteristics are not common in other countries. When the flow passes through a structure such as a weir, discontinuous flow occurs. In terms of numerical simulation, it affects the numerical instability due to the balance between the flow term and the source term. In order to solve these problems, many researchers used empirical formulas or numerical scheme simplification. Recently, researches have been conducted to use more accurate numerical scheme. K-River was developed to reflect the characteristics of domestic rivers and calculate the discontinuous flow more accurately. For the verification of K-River, 1) numerical experiment simulations with a bump in the bed, 2) laboratory experiment of hydraulic jump simulation, 3) real river were performed. K-River verified its applicability by simulating results similar to the exact solution and observed value in all simulations.

• Ecology and Resilient Infrastructure
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• v.7 no.1
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• pp.53-62
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• 2020

The present study aimed to investigate the impact of the restoration of the restoration technique on fish habitat using a physical habitat simulation in the Wonju-cheon Stream, Korea. The target species were Pungtungia herzi, Zacco platypus, and Zacco Koreanus, a dominant and sub-dominant species in the Wonju-cheon Stream. The River2D model was used for the computation of the flow and the habitat suitability index model was used to estimate the quality and quantity of habitat using habitat suitability curve. To assess the impact of pool-riffle sequence on change of fish habitat, this present study conducted using the each representative distance, namely, 50 m, 100 m, 200 m, and 300 m. Simulation results indicated that the pool-reffle sequence significantly increased the habitats for the target species than the result without considering pool-riffle sequence. On average, 53% of the Weighted Usable Area (WUA) increased due to pool-riffle sequence in the study area.

• Journal of Wetlands Research
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• v.19 no.2
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• pp.181-192
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• 2017

Analysis using a numerical model is important to understand the sediment transport mechanism associated with erosion and sedimentation near weirs and other hydraulic structures within riverine systems. The local riverbed change near a hydraulic structure (Gangjeong-Goryong multi-function weir in the Nakdong river) was analyzed in order to examine the effect of hydraulic structures on local bed change. A 2D numerical model (CCHE-2D) was employed to simulate the sedimentation and erosion over a reach (25 km) including the weir. For the calibration and verification of the model, rainfall data from a real event (Typoon 'Ewiniar' in 2006) were used for flow and stage simulation. And the simulated results show a good agreement with the observed data for the whole domain. From the result, it was found that the installation and operation of the weir could aggravate bed changes by typhoon between movable weirs, and which resulted in redistribution of sediment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1441-1449
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• 2015

At the bends of a river, the deflected flow of high energy erodes the embankment and transports sediment, ultimately changing the river's course. Such phenomena lead to instability of the embankment and may cause serious problems for nearby roads, land, or riverside structures. This study intends to analyze the characteristics of hydraulic flow at S-shaped bends after the installation of Riprap Weirs designed to prevent changes in a river's course and embankment erosion. An experimental channel was constructed by a two-dimensional CCHE2D model, and analyzed the characteristics of hydraulic flow with and without the Riprap Weirs. Also, the characteristics of hydraulic flow at the inner and outer sides of river bends and at points near reservoirs were analyzed, depending on the intervals between the Riprap Weirs.

• Journal of Korea Water Resources Association
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• v.39 no.4 s.165
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• pp.347-362
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• 2006

In this study, a 2-D flood inundation model was developed to evaluate the impact of levee failure in a natural basin for flood analysis. The model was applied to analyze the inundation flow from the levee break of Gamcheon river during the typhoon Rusa on October 31 through September 1, 2002. To verify the simulated results, wide range field surveys have been performed including the collection of NGIS database, land use condition, flooded area, and flow depths. Velocity distributions and inundation depths were presented to demonstrate the robustness of the model. Model results have good agreements with the observed data in terms of flood level and flooded area. The model is able to compute maximum stage and peak discharge efficiently in channel and protected lowland. Methodology considering radar-rainfall estimation using cokriging scheme, flood-runoff and inundation analysis in this study will contribute to the establishment of the national integrated flood disaster prevention system and the river or protect lowland management system.

• Journal of Korean Society on Water Environment
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• v.31 no.1
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• pp.35-41
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• 2015

This study focuses on whether a physical habitat model, River2D, is useful to assess and design stream restoration. To achieve the aim, the habitat suitability for Zacco Platypus was analyzed using River2D at midstream of the Anyang-Cheon through modifying the low flow channel and changing the flow discharge. The River2D simulation results show that the inhabited environment for Zacco Platypus is improved by increasing the sinuosity of the low flow channel, and vice versa. Also the inhabited environment for Zacco Platypus gets worse when there is no additional flow for maintenance water supply at the stream flowing through cities. In this respect, the physical habitat simulation study based on the River2D model is useful because it provides a practical guidance in designing stream restoration.