• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.4
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• pp.81-88
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• 2010

As there occurs recently and frequently a flash flood due to the climate change, a sudden local flood of great volume and short duration caused by heavy or excessive rainfall in a short period of time over a small area, it is increasing that significant danger and loss of life and property in Korea as well as the whole world. Since a flash flood usually occurs as the result of intense rainfall over small steep slope regions and has rapid runoff and debris flow, a flood rises quite quickly with little or no advance warning to prevent flood damage. The aim of this study is to quantify the severity of flash food by estimation of a flash flood index(FFI) from probability rainfall data in a study basin. FFI-D-F(FFI-Duration-Frequency) curves that present the relative severity of flash flood are developed for a study basin to provide regional basic information for the local flood forecasting and warning system particularly in ungauged catchments. It is also expected that FFI-D-F curves can be utilized for evaluation on flash flood mitigation ability and residual flood risk of both existing and planned flood control facilities.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.3
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• pp.148-156
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• 2002

The coastline of Hampyung Bay, southwestern coast of Korea, was examined and measured in the field for the understanding of geomorphic changes and sea-cliff erosion processes. The Hampyung-Bay coastline is characterized by steep-face slope and soft soil and/or intensively weathered rock composition. Saw teeth-shaped coastline, and relict weathered basement-rock and "Island Stack" exposed on the beach surface are peculiar geomorphic features indicating active sea-cliff erosion. The coastline in the study area is continuously retreating with the following cyclic process: erosion of cliff base, gravitational landslide or mass wasting, formation of talus, and then erosion and removal of talus. In this study, sea-level rise during summer in the west coast of Korea is suggested as one of the key factors fur the removal of soil taluses and, thereby, accelerating sea-cliff erosion.f erosion.

• Journal of Wetlands Research
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• v.12 no.3
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• pp.155-163
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• 2010

The flash flood is characterized as flood leading to damage by heavy rainfall occurred in steep slope and impervious area with short duration. Flash flood occurs when rainfall exceeds Flash Flood Guidance(FFG). So, the accurate estimation of FFG will be helpful in flash flood forecasting and warning system. Say, if we can reduce the uncertainty of rainfall-runoff relationship, FFG can be estimated more accurately. However, since the rainfall-runoff models have their own parameter characteristics, the uncertainty of FFG will depend upon the selection of rainfall-runoff model. This study used four rainfall-runoff models of HEC-HMS model, Storage Function model, SSARR model and TANK model for the estimation of models' uncertainties by using Monte Carlo simulation. Then, we derived the confidence limits of rainfall-runoff relationship by four models on 95%-confidence level.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.3
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• pp.313-321
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• 2012

Korea has been continuously affected by landslides, as 70% of the land is covered by mountains and most of annual rainfall concentrates between June and September. Recently, abrupt climate change affects the increase of landslide occurrence. Gangwon region is especially suffered by landslide damages, because the most of the part is mountainous, steep, and having shallow soil. In this study, a landslide risk assessment model was developed by applying logistic regression to the various data of Duksan-ri, Inje-eup, Inje-gun, Gangwon-do, which has suffered massive landslide triggered by heavy rain in July 2006. The information collected from field investigation and aerial photos right after the landslide of study area were stored in GIS DB for analysis. Slope gradient entered in two ways-as categorical variable and as linear variable. Error matrix for each case was made, and developed model showed the classification accuracy of 81.4% and 81.9%, respectively.

• Journal of Life Science
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• v.24 no.8
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• pp.813-819
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• 2014

The spatial distribution of geographical distances at five natural populations of Camellia japonica in Busan, Korea was studied. The four plots (Mollundae, Gadeok-do, Du-do, and Jwiseum) of C. japonica were uniformly distributed in the forest community and only one plot (Amnam-dong) was aggregately distributed in the forest community. Morisita index is related to the patchiness index showed that the plot $20m{\times}50m$ had an overly steep slope when the area was larger than $20m{\times}20m$, which indicated that the degree of aggregation increased significantly with increasing quadrat sizes, while the patchiness indices did not change from the plot $5m{\times}10m$ to $10m{\times}10m$. The spatial structure was quantified by Moran's I, a coefficient of spatial autocorrelation. Ten of the significant values (76.9%) were positive, indicating similarity among individuals in the first 4 distance classes (80 m), i.e., pairs of individuals with dissimilarity characteristics can separate by more than 100 m.

• Journal of the Speleological Society of Korea
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• no.68
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• pp.99-120
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• 2005

It is a wrong decision to use only topographic and geological maps for the study of pediment morphology in Korea. For the study of pediment morphology it is necessary to survey the earth structure by field techniques. In Korea, pediments are mostly found in granite areas with hardrock cover. But, pediments also developed in gneiss areas and what is worse in limestone areas. So, all areas in Korea developed pediment morphology. Only in South Korea pediments show a direction from south to north or from west to east. They developed only in right angles to each other, either parallel or in right angles to the strike, depending on the bedrock structure. Pediments are found in two levels. The upper level pediments are correlated with the lower level erosion surface. Besides this pediments are found in Hoenggye-ri of the Taegwolryong area in a third level 800m above sea level. The pediments developed in basins, at the lower margins of steep slopes dividing three levels of erosion surfaces and around the residual mountains on the erosion surfaces. The first belong to the early stage of pedimentation, the second to the middle stage and the third to the last stage. Also, in Korea monadnock and residual mountain have developed the pediments are correlated the slope of the hinter mountains. Akagki states that the only pedimentation times have been times of arid climate and that they are dissected by gulley erosion with climatic change, but writer's study proves that pedimentation takes place with eustatic movement, reckless defore-station and convectional rain. These facts indicate that the landforms, geological character and process of erosional cycle of the pediments in Korea resemble much those in the Chugoku Mountains of south wertern Japan, but they are larger in scale than those in the Chugoku Mountains. In conclusion, while Akagki emphasizes the geological character and climatic change in pedimentation, the writer studies prove that eustatic movements, especially the sea level rise after the Wurm age are important factors for pedimentation. Besides this the author's studies allow a classification of gentle slopes.

• Magazine of the Korean Society of Agricultural Engineers
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• v.23 no.2
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• pp.61-69
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• 1981

The paddies in the hillsides in Gonggeun-myeon, Hoingseong-gun, Kangweon-do keep a steep slope and run in and out. A land consolidation in such an area, therefore, will require high ratio of land loss and a large amount of earth moving if it follows the existing design criteria to separate drainage and irrigation ditches in a scheme. Due to the consequent decrease in construction cost, the project has not been envisaged. in order to secure the introduction of small-medium size farm machineries into the paddies, farm plots were planned to be straight and drainage with taking care of topography. Findings from the comparison of methodologies are as follows. 1. In places with a solpe of more than 1/30, a reduction in earth moving can be expected with parallel plots to the contours. 2, For the sake of effective using of farm machineries, it is thought that a plot should be running straight parallel to the contours and the ratio of length and width of a plot be more than six. 3. In places with a slop of more than 1/10, a reduction in earth moving and a effective introduction of farm-machineries can he expected with straight parllel plots to the contours. But it is undesirable to introduce a scheme in this places because of the difficulties in acreage computation and farmers' hesitation. 4. The system with a canal for both irrigation and drainage is highly effective to decrease the ratio of land loss as well as construction cost. 5. Parallel plots to the contours and a canal for both irrigation and drainage are highly effective in the decrease in construct cost. 6. To avoid the subdivision of a cooperation in farming is desirable of a plots, has more than two owners.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.26-26
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• 2012

The Kurobe river, which runs through eastern Toyama Prefecture is one of the most famous rivers for wild water because of its steep slope in the range from 1/5 to 1/120. This river forms an alluvial fan in the range up to 13 kilometers from the sea. In this region, significant seepage flow occurs and thus the stream sometimes been intermitted. Moreover, the amount of seepage flow seems to vary with the groundwater level of the region. To keep the river environment healthy for flora and fauna, especially to conserve good condition for spawning of fishes, an appropriate environmental flow should be maintained in the river. To achieve this target, controlling of the upstream reservoir has to be studied in depth. One of the major problems to decide the amount of water to be released from the reservoir to maintain the environmental flow is to estimate the amount of water leaked into the groundwater from the river. This phenomenon is affected by the river flow rate as well as the groundwater level in the alluvial fan and the conditions vary in space and time. Thus, a grid-based hydrological cycle analysis model NK-GHM has been applied to clarify the hydrological cycle componentsin this area including seepage/discharge from/to the river. The model was tested by comparing with river flow rate, groundwater levels and other observations and found that the model described those observations well. Consequently, the seepage from the Kurobe river was found significant but it was also found that the groundwater in this region has been preserved by the recharge from the irrigation water supply into paddy fields in the alluvial fan.

• Journal of Korea Water Resources Association
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• v.39 no.1 s.162
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• pp.23-33
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• 2006

In this study, application potential of SINMAP, a GIS-based landslide hazard mapping tool, is evaluated through a case study. Through the application to the severe landslide events occurred during a heavy storm in 1991 on the Mt. Dalbong area about 78 kilometers south from Seoul, SINMAP successfully spotted most landslide sites. The effects and proper ranges of three calibration parameters of SINMAP, i.e. the soil internal friction angle, the combined cohesion of tree roots and soil, and T/R, were examined through comparison of predicted landslides with the landslide inventory data. From the findings of this study, it seems that SINMAP could be used as an effective screening tool for landslide hazard mapping especially for mountain areas with fairly steep slopes and relatively thin soil layers.

• Economic and Environmental Geology
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• v.54 no.6
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• pp.717-731
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• 2021

We analyzed the characteristics of the habitat environment for the Seonam study area in Ulsan, the southern shore of the East Sea using bathymetry and seafloor environment data. The depth of the study area ranges from about 0 m to 23 m. In the west of the study area, the water depth is shallow with a gentle slope, and the water depth becomes deeper with a steep slope in the east. Due to the right-lateral strike-slip faults located in the continental margin of the East Sea, the fracture surfaces of the seabed rocks are mainly in the N-S direction, which is similar to the direction of the strike faults. Three seafloor types (conglomeratic-grained sandy, coasre-graiend sandy, fine-grained sandy) and rocky bottom area have been classified according to the analyses of the bathymerty, seafloor image, and surface sediment data. The rocky bottom areas are mainly distributed around Seaoam and in the northern and southern coastal area. But the intermediate zone between Seonam and coastal area has no rocky bottom. This intermediate area is expected to have active sedimentation as seawater way. The sandy sediments are widely distributed throughout the study area. Underwater images and UAV images show that Cnidarians, Brachiopods, Mollusks are mostly dominant in the shallow habitat and various Nacellidae, Mytilidae live on the intertidal zone around Seonam. Annelida and Arthropod are dominant in the sandy sediments. The distribution of marine organism in the study area might be greatly influenced by the seafloor type, the composition and particle size distribution of the seafloor sediments. The analysis of habitat environment mapping with bathymetry, seafloor data and underwater images is supposed to contribute to the study of the structure and function of marine ecosystem.