• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.5C
• /
• pp.191-198
• /
• 2009

It has been reported in Korea that surface slope failures in weathered soil are mainly caused by downward infiltration due to rainfall. These failures are triggered by the deepening of the wetting band in soils accompanied by a decrease in matric suction induced by the water infiltration. So, a need exists that these trends of wetting path in gneiss weathered soils, which is commonly found in Korea, are assessed by phenomenological approach. In this paper, numerical analyses of unsaturated soil slope under rainfall conditions are presented based on the wetting path soil-water characteristic curve in the laboratory. As the field SWCC matches well with the wetting path of the laboratory SWCC from the literatures, it seems reasonable to adopt the laboratory wetting SWCC as an upper boundary condition in the assessment of unsaturated slope instability.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.10 no.1
• /
• pp.124-135
• /
• 2007

The purpose of this study is to analyze the hydraulic behavior in a stream reach using SMS RMA-2 model with a series of dynamic boundary conditions of main stream and lateral flows simulated by WMS HEC-1 program. For the stream reach (10.5 km) between Gongdo and Pyeongtaek water level gauge stations of Anseongcheon, the model simulated two dimensional flow characteristics by applying dynamic flow conditions of rainfall frequencies of 50, 100, 500, and 1,000 years for the main stream and three tributaries. The temporal flow behavior successfully simulated and the results showed that the distribution of mean velocity and water level within the stream reach increased according to the increase of flow frequency. Especially, the flow velocity sensibly increased at the near downstream of lateral inflow as the width of main stream is narrower.

• Economic and Environmental Geology
• /
• v.32 no.2
• /
• pp.177-187
• /
• 1999

Gravity, magnetic and VLF surveys were conducted to investigat the structural stability and hazards associated with the Ubong landfill in Pohang City, which has been built to dump industrial wastes. In 1994, the collapse of a bank happened in the 6th landfill site due to sudden heavy rain, and a large quantity of waste materials flowed out to the nearby landfill sites, factories and roads. We used $10{\times}10m$ resolution DEM data for gravity reductions. The maximum variation of the terrain effect in the survey area is about 0.5 mgal and the terrain effect is large in the vicinity of bank boundary. The Bouguer gravity anomaly map shows the effect due to the variatino of thickness and type of waste materials. The small negative gravity anomaly increases from the 9th site to the 6th site. The small negative gravity anomaly of the 9th site reflects the relatively shallow dumping depth of average 14.5 m in this site and increased density of waste materials by the repeated stabilization process of soil overlaying. The 6th site is located at the center of the former valley and rainfall and groundwater are expected to flow from south-east to north-west. Therefore, considering the previous accident of mixing waste and bank materials at the north-west boundary of the landfill, there may be some environmental problems of leakage of contaminated water and bank stability. The complex inversion technique using Simulated annealing and Marquardt-Levenberg methods was applied to calculate three-dimensional density distribution from gravity data. In the case of 6th site, it is apparent that the landfill had been dumped in four sectors. However, most part of the 9th site and showed that high magnetic industrial wastes were concentrated in the 6th site. The result of magnetic survey showing low magnetic anomalies along the boundaries of two sites is similar to that of gravity data. The VLF data also reveals four divided sectors in the 6th site, and overall anomaly trend indicates the directio of former valley.

• Journal of Korean Society on Water Environment
• /
• v.24 no.4
• /
• pp.442-451
• /
• 2008

We analyzed characteristics of rainfall-runoff for the channel of Yongwon area made by a new port construction. And we conducted inundation analysis on the region of lower elevation near the coast. SWMM5 was calibrated with the storm produced by the typhoon Megi from August 19 to August 20 in 2004, and was verified with the storm from August 22 to August 22 in 2004. We performed hydraulic channel routing of Yongwon channel about typhoon Megi from August 19 to August 20 in 2004 by UNET model which is a hydraulic channel routing. The simulated runoff hydrographs were added to the new stream as lateral inflow hydrographs and a watershed runoff hydrograph was the upstream boundary condition. The downstream boundary condition data were estimated by the measured stage hydrographs. The maximum stage that was calculated by hydraulic channel routing was higher than the levee of inundated region in typhoon Megi. Thus we can suppose an inundation to have been occurred. We performed inundation analysis about typhoon Megi from August 19 to August 20 in 2004 and flood discharge of return period 10~150 years. And we estimated each inundation area. The inundation areas by return periods of storms were estimated by 3.4~5.7 ha. The causes of inundation are low heights of levee crests (D.L. 2.033~2.583 m), storm surges induced by typhoons and reverse flow through the coastal sewers (D.L. -0.217~0.783 m). A result of this study can apply to establish countermeasure of a flood disaster in Yongwon.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.2
• /
• pp.25-35
• /
• 2009

Slope failures are one of the significant disasters which causes lots of human casualties and huge financial losses every year. Previous researches on the slope failure have indicated that most accidents are closely related to the pore water pressure in the slope due to rainfall during the rainy seasons or stormy weather conditions. It would be therefore appropriate to consider the effect of pore water pressure in the design of slopes. As the existing slopes are generally reinforced by plants and other slope protecting measures, their boundary conditions are highly complicated. In this paper an attempt to develop a new modeling and analysis technique of slopes is proposed by including pore water pressure and adopting the coupled finite element method. Non-reinforced and reinforced slope models are considered. Representative analysis showed that the numerical modeling considering pore water pressure is appropriate in slope stability analysis. Flow behavior in the slopes is identified for various hydraulic boundary conditions. It is also shown that the effect of pore water pressure on slope stability is significant.

• Journal of Korea Water Resources Association
• /
• v.38 no.8 s.157
• /
• pp.655-664
• /
• 2005

A real-time monitoring and modeling system (RTMMS) for rainfall-induced turbidity flow, which is one of the major obstacles for sustainable use of reservoir water resources, is under development. As a prediction model for the RTMMS, a laterally integrated two-dimensional hydrodynamic and water quality model, CE-QUAL-W2 was tested by simulating the temperature stratification, density flow regimes, and temporal and spatial distributions of turbidity in a reservoir. The inflow water temperature and turbidity measured every hour during the flood season of 2004 were used as the boundary conditions. The monitoring data showed that inflow water temperature drop by 5 to $10^{\circ}C$ during rainfall events in summer, and consequently resulted in the development of density flow regimes such as plunge flow and interflow in the reservoir. The model showed relatively satisfactory performance in replicating the water temperature profiles and turbidity distributions, although considerable discrepancies were partially detected between observed and simulated results. The model was either very efficient in computation as the CPU run time to simulate the whole flood season took only 4 minutes with a Pentium 4(CPU 2.0GHz) desktop computer, which is essentially requited for real-time modeling of turbidity plume.

• The Korean Journal of Quaternary Research
• /
• v.21 no.1
• /
• pp.15-26
• /
• 2007

A wide tree-ring data network from Western Himalayan region as well as from Central and Peninsular India have been established by the Indian Institute of Tropical Meteorology (IITM), Pune, India. This includes several ring width and density chronologies of Himalayan conifers (Pinus, Picea, Cedrus, Abies)covering entire area of Western Himalaya and teak (Tectona grandis L.F.) from central and peninsular India. Many of these chronologies go back to $15^{th}$ century. Tree-ring based reconstructed pre-monsoon (March-April-May) summer climate of Western Himalaya do not show any significant increasing or decreasing trend since past several centuries. High altitude tree-ring chronologies near tree line-glacier boundary are sensitive to the winter temperature. Unprecedented higher growth in recent decades is closely associated with the warming trend over the Himalayan region. Dendroclimatic analysis of teak (Tectona grandis) from Central and Peninsular India show significant relationship with pre-monsoon and monsoon climate. Moisture index over the region indicates strong association with tree-ring variations rather than the direct influence of rainfall. It is evident that, two to three consecutive good monsoon years are capable of maintaining normal or above normal tree growth, even though the following year is low precipitation year.

• Proceedings of the Korea Contents Association Conference
• /
• 2009.05a
• /
• pp.432-436
• /
• 2009

Recently, damage of flood is increased because of a short of time of concentration by development and a rise in runoff discharge by frequently heavy rain. The increase of runoff discharge is resulted in not only rise of water level but also damage of lives and property around river. Therefore, it is should be the first to estimate the exact runoff discharge. And based on the estimated flood discharge, flood damage is prevented by estimating inundated area of flood. In this study, flood stage is forecasted using HEC-HMS and HEC-RAS for Namdae-stream. The peak discharges were determinated by probability rainfall with the return period. The peak discharges obtained from HEC-HMS were inputted boundary conditions for the channel routing. Flood stages were evaluated using HEC-RAS.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.1-13
• /
• 2010

Numerous landslides had occurred in Kangwondo in July 2006 and several restoration works had been done. A-day-accumulative rainfalls from July 12 to July 13 and July 15 to July 16 were 176mm and 202mm respectively. Disaster sites at which slope failures were studied to main causes of slope failures by investigating characteristics of rainfall, geological formation, topography and ground surface exploration around the boundary of landslides. In this study, a series of slope restoration work process is presented for reference which about the landsliding area in Han-Gye-Ryeong to O-Saek in Kwangwon-do where one of the most severe damaged area in 2006. The slope restoration work process includes site investigation, analysis on affected factor, restoration or reinforcing method design, construction procedure and recent status of that area. Also several considering points are suggested while design and construction for the reference at the other restoration works.

• Atmosphere
• /
• v.26 no.3
• /
• pp.461-471
• /
• 2016

A quality check algorithm for the Weather Information Service Engine pulsed Doppler wind lidar is developed from a view point of spatial and temporal consistencies of observed wind speed. Threshold values for quality check are determined by statistical analysis on the standard deviation of 3-component of wind speed obtained by a wind lidar, and the vertical gradient of horizontal wind speed obtained by a radiosonde system. The algorithm includes carrier-to-noise ratio (CNR) check, data availability check, and vertical gradient of horizontal wind speed check. That is, data sets whose CNR is less than -29 dB, data availability is less than 90%, or vertical gradient of horizontal wind speed is less than $-0.028s^{-1}$ or larger than $0.032s^{-1}$ are classified as 'doubtful', and flagged. The developed quality check algorithm is applied to data obtained at Bucheon station for the period from 1 to 30 September 2015. It is found that the number of 'doubtful' data shows maxima around 2000 m high, but the ratio of 'doubtful' to height-total data increases with increasing height due to atmospheric boundary height, cloud, or rainfall, etc. It is also found that the quality check by data availability is more effective than those by carrier to noise ratio or vertical gradient of horizontal wind speed to remove an erroneous noise data.