• Journal of Korea Water Resources Association
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• v.34 no.3
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• pp.275-285
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• 2001

Since the majority of streamflow during dry periods is provided by groundwater storage, the streamflow depends on a basin moisture state recharged from rainfall during wet periods. This hydrologic characteristics dives good condition to predict long-term streamflow if the basin state like groundwater recharge is known in advance. The objective of this study is to examine groundwater recharge effect to monthly streamflow, and to attempt monthly streamflow prediction using estimated groundwater recharge. The ground water recharge is used as an independent variable with streamflow and precipitation to construct multiple regression models for the prediction. Correlation analysis was performed to assess the effect of groundwater carry-over to streamflow and to establish the associations among independent variables. The predicted streamflow shows that the multiple regression model involved groundwater recharge gives improved results comparing to the model only using streamflow and precipitation as independent variables. In addition, this paper shows that the prediction model with the effect of groundwater carry-over taken into account can be developed using only precipitation.

• Journal of the Korean GEO-environmental Society
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• v.16 no.8
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• pp.45-49
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• 2015

Using 2D numerical analysis that covers the largest section of the dam body, a process is generally performed when evaluating its stability against seepage. The quantity of seepage is first obtained by assuming that its bottom topography is in the simple form of a rectangle, it is then calculated by reflecting its sectional shape during this process of analyzing the seepage quantity. Considering that various forms of dams are being constructed on various types of ground, thanks to more recent technological advances, it is judged more appropriate to draw a conclusion by means of the results on reflecting the realistic shape and topographical conditions of the dam body through 3D numerical analysis. Therefore, this study intends to present a method designed to carry out safety management by evaluating the correct quantity of water leakage that passes only through the dam body, having excluded other factors that include the amount of rainfall through the 3D FEM analysis.

• Journal of the Korean Geosynthetics Society
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• v.12 no.2
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• pp.35-42
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• 2013

Recently, construction of reinforced earth structure using geosynthetics has been increased because it has advantages such as construction efficient, cost effectiveness and appearance aspect against existing gravity or cantilever retaining wall. However due to the climate change in Korea excessive inflow of ground water and surface water from heavy rainfall could affect the stability of reinforced retaining wall seriously. So the discharge capacity of drains should be evaluated by using experimental method in the design of reinforced earth wall. In this study, instead of concrete block used in most of the retaining wall, eco-friendly porous soilbag was used. This paper describes the test method and result of the laboratory testing for determination of discharge capacity utilizing PBDs.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.19 no.3
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• pp.103-119
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• 2016

This study aims to assess habitat feature on the large-scale spawning ground of the Boreal Digging Frog Kaloula borealis in Daemyung retarding basin of Daegu, and to analyze the relationships between species abundance and meteorological factors for each habitat. Fifty-seven(57) pitfalls were installed to collect species abundance of 4 survey regions, and high-resolution satellite image, soil sampling equipment, digital topographic map, and GPS were used to develop habitat features such as terrain, soil, vegetation, human disturbance. The analysis shows that the frog is most abundant in sloped region with densely herbaceous cover in southern part of the retarding basin. In the breeding season, lowland regions, where Phragmites communis and P. japonica dominant wetlands and temporary ponds distributed, are heavily concentrated by the species for spawning and foraging. Located in between legally protected Dalsung wetands and lowland regions of the retarding basin, riverine natural levee is ecologically important area as core habitat for Kaloula borealis, and high number of individuals were detected both breeding and non-breeding seasons. Temperate- and pressure-related meteorological elements are selected as statistically significant variables in species abundance of non-breeding season in lowland and highland regions. However, in sloped regions, only a few variables are statistically significant during non-breeding season. Moreover, breeding activities in sloped regions are statistically significant with minimum temperature, grass minimum temperature, dew point temperature, and vapor pressure. Significant meteorological factors with habitat features are effectively applied to establish species conservation strategy of the retarding basin and to construct for avoiding massive road-kills on neighboring roads of the study sites, particularly post-breeding movements from spawning to burrowing areas.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.962-964
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• 2003

In 2002 Thailand was faced with severe flooding in the North, Northeast and Central parts of the country caused by heavy rainfall of the monsoonal depression which brought about significant damages. According to the report by the Ministry of Interior and the Ministry of Agricultural and Co-operatives, the total damages were estimated to be about 6 billion bath. More than 850,000 farmers and 10 million livestock were effected. An area of 1,450,000 ha of farmland in 59 Provinces were put under water for a prolonged period. Satellite imageries were employed for mapping and monitoring the flood-inundated areas, flood damage assessment, flood hazard zoning and post-flood survey of river configuration and protection works. By integrating satellite data with other updated spatial and non-spatial data, likely flood zones can be predicted beforehand. Some examples of satellite data application to flood dis aster mitigation in Thailand during 2002 using mostly Radarsat-1 data and Landsat-7 data were illustrated and discussed in the paper. The results showed that satellite data can clearly identify and give information on the status, flooding period, boundary and damage of flooding. For comprehensive flood mitigation planning, other geo-informatic data, such as the elevation of topography, hydrological data need to be integrated. Ground truth data of the watershed area, including the water level, velocity, drainage pattern and direction were also useful for flood forecasting in the future.

• Korean Journal of Medicinal Crop Science
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• v.17 no.3
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• pp.204-209
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• 2009

This study was conducted to assess water movement in paddy-upland rotation soil scheduled for ginseng cultivation through the measurement of infiltration and permeability of soil water. Soil sample was divided with four soil layers. The first soil layer (to 30cm from top soil) was loamy sand, the second and the third soil layers (30$\sim$70 ㎝) were sand, and the fourth (< 120 ㎝) was sandy loam. The soil below 130 ㎝ of fourth soil layer was submerged under water. The shear strength, which represents the resisting power of soil against external force, was 3.1 kPa in the first soil layer. This corresponded to 1/8 of those of another soil layer and this value could result in soil erosion by small amount of rainfall. The rates of infiltration and permeability depending on soil layers were 39.86 cm $hr^{-1}$ in top soil, 2.34 cm $hr^{-1}$ in 30$\sim$70 ㎝ soil layer, 5.23 cm $hr^{-1}$ and 0.18 cm $hr^{-1}$ in 70$\sim$120 ㎝ soil layer, with drain tile, and without drain tile, respectively. We consider that ground water pooled in paddy soil and artificial formation of soil layer could interrupt water canal within soil and affect negatively on water movement. Therefore, we suggest that to drain at 5 m intervals be preferable when it makes soil dressing or soil accumulation to cultivate ginseng in paddy-upland rotation soil to reduce failure risk of ginseng cultivation.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.396-396
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• 2015

Frequent urban floods affect the human safety and economic properties due to a lack of the capacity of drainage system and the increased frequency of torrential rainfall. The drainage system has played an important role in flooding control, so it is necessary to establish the effective countermeasures considering the connection between drainage system and surface flow. To consider the connection, we selected SWMM5 model for analyzing transportation capacity of drainage system and FLUMEN model for calculating inundation depth and time variation of inundation area. First, Thiessen method is used to delineate the sub-catchments effectively base on drainage network data in SWMM5. Then, the output data of SWMM5, hydrograph of each manhole, were used to simulate FLUMEN to obtain inundation depth and time variation of inundation area. The proposed method is applied to Sadang area for the event occurred in $27^{th}$ of July, 2011. A total of 11 manholes, we could check the overflow from the manholes during that event as a result of the SWMM5 simulation. After that, FLUMEN was utilized to simulate overland flow using the overflow discharge to calculate inundation depth and area on ground surface. The simulated results showed reasonable agreements with observed data. Through the simulations, we confirmed that the main reason of the inundation was the insufficient transportation capacities of drainage system. Therefore cooperation of both models can be used for not only estimating inundation damages in urban areas but also for providing the theoretical supports of the urban network reconstruction. As a future works, it is recommended to decide optimized pipe diameters for efficient urban inundation simulations.

• Journal of the Korean GEO-environmental Society
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• v.24 no.5
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• pp.21-28
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• 2023

In this paper, an experimental study was conducted to present the properties of rapid hardening composite mat, and a numerical analysis was carried out to analyze the slope protection effect of the mats based on ground conditions, rainfall, slope gradient and soil height. As a result, the application of rapid hardening composite mat increased the slope safety factor in all conditions, and the increase rate of safety factor showed an average of 40% increase both in dry and rainy seasons. Through these research findings, the protective effect of the rapid hardening composite mat on sloping surfaces has been proven, and it is suggested that the rapid hardening composite mat is suitable for application in areas where slope failure or collapse is expected.

• Journal of the Korean Geotechnical Society
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• v.25 no.1
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• pp.31-40
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• 2009

This paper presents a new approach of risk evaluation method for the reinforced slopes. In order to perform this study, the existing stability and risk evaluation methods are reviewed and analysed in terms of rainfall, ground condition, and drain conditions. According to the characteristic of the reinforced slopes improved by internal and external reinforcement, the nineteen influence factors are determined in order to develop new risk analysis model based on 'Interaction matrix' approach suggested by Hudson (1991). Using new approach of slope risk analysis model, the weighting values for interaction factors are analysed and determined. Based on new slope risk evaluation approach, the slope risk index, namely SRI (Slope Risk Index) is developed in this study to apply the evaluation of the reinforced slopes. In order to verify the SRI, a total of 15 cases are studied and analysed. The analysed results are compared and evaluated. According to the results, it is deduced that new slope risk evaluation method (SRI approach) IS very useful and practically a reliable method to evaluate the existing slopes.

• Geomechanics and Engineering
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• v.34 no.3
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• pp.267-284
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• 2023

Landslides are one of the most dangerous phenomena and natural disasters. Landslides cause many human and financial losses in most parts of the world, especially in mountainous areas. Due to the climatic conditions and topography, people in the northern and western regions of Iran live with the risk of landslides. One of the measures that can effectively reduce the possible risks of landslides and their crisis management is to identify potential areas prone to landslides through multi-criteria modeling approach. This research aims to model landslide potential area in the Oshvand watershed using a support vector machine algorithm. For this purpose, evidence maps of seven effective factors in the occurrence of landslides namely slope, slope direction, height, distance from the fault, the density of waterways, rainfall, and geology, were prepared. The maps were generated and weighted using the continuous fuzzification method and logistic functions, resulting values in zero and one range as weights. The weighted maps were then combined using the support vector machine algorithm. For the training and testing of the machine, 81 slippery ground points and 81 non-sliding points were used. Modeling procedure was done using four linear, polynomial, Gaussian, and sigmoid kernels. The efficiency of each model was compared using the area under the receiver operating characteristic curve; the root means square error, and the correlation coefficient . Finally, the landslide potential model that was obtained using Gaussian's kernel was selected as the best one for susceptibility of landslides in the Oshvand watershed.