• Title/Summary/Keyword: mountainous valley

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Wind tunnel modeling of flow over mountainous valley terrain

  • Li, C.G.;Chen, Z.Q.;Zhang, Z.T.;Cheung, J.C.K.
    • Wind and Structures
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    • v.13 no.3
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    • pp.275-292
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    • 2010
  • Wind tunnel experiments were conducted to investigate the wind characteristics in the mountainous valley terrain with 4 simplified valley models and a 1:500 scale model of an existing valley terrain in the simulated atmospheric neutral boundary layer model. Measurements were focused on the mean wind flow and longitudinal turbulence intensity. The relationship between hillside slopes and the velocity speed-up effect were studied. By comparing the preliminary results obtained from the simplified valley model tests and the existing terrain model test, some fundamental information was obtained. The measured results indicate that it is inappropriate to describe the mean wind velocity profiles by a power law using the same roughness exponent along the span wise direction in the mountainous valley terrain. The speed-up effect and the significant change in wind direction of the mean flow were observed, which provide the information necessary for determining the design wind speed such as for a long-span bridge across the valley. The longitudinal turbulence intensity near the ground level is reduced due to the speed-up effect of the valley terrain. However, the local topographic features of a more complicated valley terrain may cause significant perturbation to the general wind field characteristics in the valley.

Flood Runoff Computation for Mountainous Small Basins using HEC-HMS Model (HEC-HMS 모델을 이용한 산지 소하천유역의 홍수유출량 산정)

  • Chang, In-Soo
    • Journal of the Korean Society of Industry Convergence
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    • v.7 no.3
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    • pp.281-288
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    • 2004
  • The objective of this study is to propose a methodology of the flood runoff analysis in steep mountainous basins and the analysis basin is the Jasa valley basin in Chungju city Analyzing the spatial pattern of the rainfall in 1994. 6 30~7.1, the seasonal rainy front was tied up in the whole central district, and the rainfall center was moving from the northern Chungbuk province to the northern Kyongbuk province and caused heavy storm. Analyzing the temporal pattern with the Huff method, the 52.5% of the rainfall was concentrated on the 3rd quartile. Rainfall frequency analysis is accomplished by five distribution types; 2-parameter Lognomal, 3-parameter Lognomal, Pearson Type III, Log-Pearson Type III and Extremal Type I distribution Rainfall-runoff analysis in Jasa valley basin was made using HEC-HMS model. Jasa valley basin was divided into 3 sub-basins and the analysis point was 3 points{A, B and C point) With the rainfall data measured by the 10 minutes, the flood runoff also was calculated by as many minutes. SCS CN model, Clark UH model and Muskingum routing model in HEC-HMS model were used to simulate the runoff volume using selected rainfall event.

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Wind Tunnel Experiments for Studying Atmospheric Dispersion in the Complex Terrain I.Dispersion in a mountainous Area (복잡한 지형내 오염물질의 대기확산 풍동실험: I. 산지지형에서의 확산)

  • 경남호;김영성;손재익
    • Journal of Korean Society for Atmospheric Environment
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    • v.8 no.3
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    • pp.169-178
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    • 1992
  • Dispersion of pollutant in a mountainous area is simulated in a wind tunnel. In the northwest side of the terrain model, the sea level is assumed. Wind from the sea initially confronts hills along the shoreline, a line of large buildings next, and finally a valley between high mountains in the south and in the east. In the northwest wind conditions, severe flow separation occurs in the lee side of hills, even beyond the building area. Pollutant from the buildings is trapped in this region and its concentration is the highest. In the west wind conditions, pollutant from the buildings flows along the hills aslant the main wind direction in this case. Since large valley is located in the downstream, pollutant tends to disperse along the valley.

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Study on the Terrestrial LiDAR Topographic Data Construction for Mountainous Disaster Hazard Analysis (산지재해 위험성 분석을 위한 지상 LiDAR 지형자료 구축에 관한 연구)

  • Jun, Kye Won;Oh, Chae Yeon
    • Journal of the Korean Society of Safety
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    • v.31 no.1
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    • pp.105-110
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    • 2016
  • Mountainous disasters such as landslides and debris flow are difficult to forecast. Debris flow in particular often flows along the valley until it reaches the road or residential area, causing casualties and huge damages. In this study, the researchers selected Seoraksan National Park area located at Inje County (Inje-gun), Gangwon Province-where many mountainous disasters occur due to localized torrential downpours-for the damage reduction and cause analysis of the area experiencing frequent mountainous disasters every year. Then, the researchers conducted the field study and constructed geospatial information data by GIS method to analyze the characteristics of the disaster-occurring area. Also, to extract more precise geographic parameters, the researchers scanned debris flow triggering area through terrestrial LiDAR and constructed 3D geographical data. LiDAR geographical data was then compared with the existing numerical map to evaluate its precision and made the comparative analysis with the geographic data before and after the disaster occurrence. In the future, it will be utilized as basic data for risk analysis of mountainous disaster or disaster reduction measures through a fine-grid topographical map.

Observation of the Cold-air Drainage and Thermal Belt Formation in a Small Mountainous Watershed by Using an Infrared Imaging Radiometer (적외선 영상 복사계를 이용한 산간집수역의 찬공기 배수와 온난대 형성 관측)

  • Yun, Jin-I.
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.13 no.2
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    • pp.79-86
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    • 2011
  • Cold-air drainage and pooling occur in most mountain valleys at night. Local climates with cold-air pooling could affect phenology and distribution of crop plants. A high resolution infrared imaging radiometer was used to visualize the cold-air drainage and thermal belt formation over a small mountainous watershed (ca. $10{\times}5{\times}1$ km for the maximum length${\times}$width${\times}$depth). Thermal images on $640{\times}480$ pixels were scanned across the Akyang valley (south of Mt. Jiri National Park) by the radiometer installed at a local peak ('Hyongjebong', 1,117 m a.s.l.) at dawn of 17 May 2011, when the synoptic condition was favorable for the surface cooling and cold-air drainage. Major findings are: (1) Cold-air drainage and accumulation was clearly identified by the lowest brightness temperature mainly at the valley bottom. (2) So-called 'thermal belt' with higher brightness temperature was found partway up the valley sidewalls and showed up to $5^{\circ}C$ departure from the valley bottom temperature. (3) Digital thermography showed feasibility for validation of the high definition geospatial temperature models currently in use for the plot-specific agrometeorological service.

A Study on Flash Flood Warning Trigger Rainfall in Mountainous Area (산악지역 돌발홍수 기준우량 결정에 관한 연구)

  • Jun, Kye-Won;Oh, Chae-Yeon
    • Journal of the Korean Society of Safety
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    • v.24 no.1
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    • pp.89-94
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    • 2009
  • The purpose of this study is to estimate the critical flood discharge and flash flood trigger rainfall for alarm system providing for a flash flood in mountainous area. The flash flood need non-linear approaching method, because rainfall-runoff is nonlinear and it is difficult to explain the existing linear rainfall-runoff. Hydrological characteristics would be utilized to apply such as hydrologic modelling or basin management. This study was effectively estimated a topographic characteristic factor of basin using the GIS. Especially, decided stream order using GIS at stream order decision that is important for input variable of GCIUH. A flash floods defined as a flood which follows shortly after a heavy or excessive rainfall event, with a few hours. In this study, we gave a definition that a critical flood for alarm is the flood when valley depth judging dangerous depth is over 0.5m depth from the bottom of channel. Result that calculate threshold discharge to use GCIUH, at the Mureung valley basin, flash flood trigger rainfall was 16.34mm in the first 20minutes when the threshold discharge was $14.54m^3/sec$.

A Three Dimensional Numerical Simulation of $SO_2$ Concentration in Relation with Atmospheric Flow in Pusan Area, Korea (부산지역에서의 대기흐름과 관련된 $SO_2$농도 3차원 수치모의)

  • 장은숙;이화운
    • Journal of Environmental Science International
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    • v.6 no.4
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    • pp.359-367
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    • 1997
  • The Characteristics of atmospheric flow and dispersion of air pollutants in the mountainous coastal area were studied using three-dimensional model by the combination of land/sea breezes and transport. It was then applied to Pusan city. As the urban area considered In this study is located in a mountainous coastal area, the atmospheric flow is strongly affected by the land/sea breezes and mountain/valley winds. The typical effects of land/sea breezes on the dispersion and the characteristics of pollutants movement in the region were analysed. The model has been proved to be an useful tool to prodict real time air pollutants transport as shown by the results of application studies In Pusan, Korea which Is an urbanized coastal area with mountainous topography. It was found that the pollutants are differently transported and concentrated as going Inland by the Influence of the sea breeze with topographic changes. By comparing the pollutants concentrations of the stimulated results with those of the observational results, It is shown that stimulated results in this study are in qualitative agreement with observational ones.

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A Study on Flash Flood Warning in Mountainous Area (산악지역 돌발홍수 경보발령 기준 설정에 관한 연구)

  • Jun, Kye-Won;Oh, Chae-Yeon;Yeon, Gyu-Bang;Lee, Seung-Chul;Jun, Byong-Hee
    • 한국방재학회:학술대회논문집
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    • 2007.02a
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    • pp.591-594
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    • 2007
  • The purpose of this study is to estimate the critical flood discharge and flash flood trigger rainfall for alarm system providing for a flash flood in mountainous. This study was effectively estimated a topographic characteristic factor of basin using the GIS. Especially, decided stream order using GIS at stream order decision that is important for input variable of GCIUH. Result that calculate threshold discharge to use GCIUH, at the Mureung valley basin, flash flood trigger rainfall was 16.34mm in the first 20 minutes when the threshold discharge was $14.54\;m^3/sec$.

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A Study of Optimal Water Supply Planning in Mountainous Area (산지유역에서의 최적용수공급방안에 관한 연구)

  • Kim, Ji-Hak;Park, Ki-Bum
    • Journal of Environmental Science International
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    • v.15 no.10
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    • pp.967-973
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    • 2006
  • In this study used tank model and specific discharge to calculate low-flow of mountain basin and supply data that need in water resources plan. Low-flow is calculated byspecific discharge and area ratio method as resulted that calculate storage of low-flow by tank model was construed that showd all similar aspect. In judged to help in water resources plan establishment calculating low-flow using model to supplement uncertainty of observed data in that calculate of low-flow ungaged mountain area. It shows by economical and realistic plan until 12 years after development that run parallel and use economic performance analysis result valley flow and groundwater. But wide area water services and Chungju dam since 12 years onward was expose that is economic.

Numerical Study on Warming Effect Due to Green House Gas in Microscale Atmospheric Domain (미기상규모 영역의 온실기체 승온효과에 관한 수치연구)

  • 이순환;서광수;김동희;황수진
    • Journal of Korean Society for Atmospheric Environment
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    • v.20 no.3
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    • pp.303-315
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    • 2004
  • The change of land use such as the construction of way in mountainous area and tunnel leads to the quantitative change of the greenhouse gas. This study tried to clarify the effect of the change of land use around Miryang Ice Valley on thermal environment of micro-meteorological scale by numerical experiment. We carried out several numerical experiment under different atmospheric conditions with different amount of greenhouse gases. Heating rate increased by the greenhouse gas in the ground level is average of 0.0073 K/day. And the increasing rate if smaller than the daily average heat crossing quantity.