• Journal of Korea Water Resources Association
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• v.40 no.5
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• pp.373-382
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• 2007

The exact resolution of channel initiation points is not so easy because of the dynamic behaviors of water movement on the hillslope. To this end, Kim, Joocheol and Kim, Jaehan(2007) have represented the channel network in real world basins for slope-area regimes using DEM. This study is its sequential content and then proposes the reliabilities of the hypothetical channel networks identified from DEM, which are assessed based on the geometric characteristics of drainage density and source-basin. The resulting drainage structures on the natural basin can be found to be depicted remarkably depending on the hypothetical channel network applied by slop-area threshold criterion. In addition, it is shown that there is a wonderful geometric similarity between the shapes of source- basin in a geomorphologically homogeneous region. Area threshold criterion could have restricted the shape of source-basin, so that it might bring about the incorrect drainage structures. But the hypothetical channel networks identified from DEM deserves special emphasis on expressing the space-filling structures nonetheless.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.321-321
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• 2022

유역 모델링은 유역에 강우의 유출 과정을 재현할 수 있는 과정이다. 과거 유역 모델링은 1차원 수준에서 유출과정을 모의하는데 그쳤으나, 기술이 발전함에 있어 입력하는 매개변수 수가 증가함에 따라 모의값의 신뢰성이 높아지고 있다. 본 연구에서는 다양한 매개변수 중 공간매개변수로써 널리 활용되고 있는 수치표고모델의 신뢰성과 범용성을 확인하고자 한다. 유역모델링 연구에 있어, 수치표고모델 정확성은 결과값의 신뢰성을 좌우하는 중요한 인자 중 하나이다. 수치표고모델이란 실제 지형이 나타내는 표고 정보를 수치화 하여 격자 안에 담은 형태의 파일로 대표적으로 DEM(Digital Elevation Models)과 DSM(Digital Surface Models)로 나눌 수 있다 DEM의 경우 해당 지형의 고도정보만을 담고있으며, DSM은 지표면 상의 나무, 건물 등 포함한 지표면의 고도를 담고 있다. 현재 NASA에서는 전 지구의 30m격자 크기로 SRTM-DSM을 제공하고 있으며, 우리나라 국토지리정보원에서도 90m 격자크기의 DEM을 제공하고 있다. 본 연구에서는 남한강 유역의 수치표고모델을 세 가지 Case로 나눠서 유출량 변화 검토를 진행하였다. 산지가 많은 남한강 유역의 10개의 소유역을 선정하였고, 다음과 같이 3개의 Case를 적용하였다. Case1, DEM 자료를 입력했을 경우, Case2, DSM 자료를 입력했을 경우, Case3 DSM+DEM 자료를 입력했을 경우, 각 Case에 대해 유출량을 산정하였고, 그 결과값을 분석하였다. 해당 유역에 세 가지 Case 모두 유출량의 변화량의 큰 차이를 보이지 않았으며, 공간매개변수 적용에 있어 타당성을 보였다. 따라서 본 연구는 인공위성을 통해 산출된 수치표고모델의 신뢰성을 확인 하였고, 활용가능성을 검토 하였다. 이에 따라 향후 연구에 수치표고모델 적용에 있어 미계측유역에도 활용가능한 연구로 기여할 수 있을 것으로 판단된다.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1089-1094
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• 2004

Numerical methods to estimate behaviors of jointed rock mass can be roughly divided into two method : discontinuous model and continuum model. Generally, distinct element method (DEM) is applied in discontinuous model, and finite element method (FEM) or finite difference method (FDM) is utilized in continuum model. To predict a behavior of discontinuous model by DEM, it is essential to understand characteristics of joints developed in rock mass through field tests. However, results of field tests can not provide full information about rock mass because field tests is conducted in limited area. In this paper, discontinuous analysis by UDEC and continuous analysis by FLAC is utilized to estimate a behavior of a tunnel in jointed rock mass. For including discontinuous analysis in continuous analysis, joints in rock mass is considered by reducing rock mass properties obtained by RMR and decreasing shear strength of rock mass. By comparing and revising two analysis results, analysis results similar with practical behavior of a tunnel can be induced and appropriate support system is decided.

• Journal of Korea Water Resources Association
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• v.53 no.7
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• pp.545-555
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• 2020

A feasibility modeling for potential hydroelectric dam site selection was suggested using 1 sec ASTGTM (ASTER Global Digital Elevation Model) and Terra/Aqua MODIS (Moderate Resolution Imaging Spectroradiometer) derived land use (MCD12Q1) data. The modeling includes DEM pre-processing of peak, sink, and flat, river network generation, watershed delineation and segmentation, terrain analysis of stream cross section and reservoir storage, and estimation of submerged area for compensation. The modeling algorithms were developed using Python and as an open source GIS. When a user-defined stream point is selected, the model evaluates potential hydroelectric head, reservoir surface area and storage capacity curve, watershed time of concentration from DEM, and compensation area from land use data. The model was tested for 4 locations of already constructed Buhang, BohyunMountain, Sungdeok, and Yeongju dams. The modeling results obtained maximum possible heads of 37.0, 67.0, 73.0, 42.0 m, surface areas of 1.81, 2.4, 2.8, 8.8 ㎢, storages of 35.9, 68.0, 91.3, 168.3×10⁶ ㎥ respectively. BohyunMountain and Sungdeok show validity but in case of Buhang and Yeongju dams have maximum head errors. These errors came from the stream generation error due to ASTGTM. So, wrong dam watershed boundary limit the head. This study showed a possibility to estimate potential hydroelectric dam sites before field investigation especially for overseas project.

• Korean Journal of Remote Sensing
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• v.23 no.6
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• pp.567-573
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• 2007

Tidal channel development is influenced by sediment type, grain size, composition and tidal current. Tidal channels are usually characterized by channel formation, density and shape. Quantitative analysis of tidal channels using remotely sensed data have rarely been studied. The objective of this study is to quantify tidal channels in terms of fractal dimension and compare different inter-tidal channel patterns and compare with DEM (Digital Elevation Model). For the fractal analysis, we used box counting method which had been successfully applied to streams, coastlines and others linear features. For a study, the southern part of Ganghwado tidal flats was selected which know for high dynamics of tidal currents and vast tidal flats. This area has different widths and lengths of tidal channels. IKONOS was used for extracting tidal channels, and the box counting method was applied to obtain fractal dimensions (D) for each tidal channel. Yeochari area where channels showed less dense development and low DEM had low fractal dimenwion near $1.00{\sim}1.20$. Area (near Donggumdo and Yeongjongdo) of dendritic channel pattern and high DEM resulted in high fractal dimension near $1.20{\sim}1.35$. The difference of fractal dimensions according to channel development in tidal flats is relatively large enough to use as an index for tidal channel classification. Therefore we could conclude that fractal dimension, channel development and DEM in tidal channel has high correlation. Using fractal dimension, channel development and DEM, it would be possible to quantify the tidal channel development in association with surface characteristics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.659-665
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• 2016

The limit equilibrium method (LEM) is commonly used for slope design and stability analysis because it is easy to simulate slope and requires short calculating time. However, LEM cannot adequately simulate ploughing failure in a footwall slope with a joint set dipping parallel with slope, e.g. bedding joint set. This study performed parametric study to analyze the influence factors on ploughing failure using UDEC which is a commercial two-dimensional DEM (Distinct Element Method)-based numerical program. The influence of joint structure and properties on stability of a footwall slope against ploughing failure was investigated, and the factor of safety was estimated using the shear strength reduction method. It was found that the stability of footwall slope against ploughing failure strongly relies on dip angle of conjugate joint, and the critical bedding joint spacing and the critical length of slab triggering ploughing failure are also affected by dip angle of conjugate joint. The results obtained from this study can be used for effective slope design and construction including reinforcement.

• Journal of Korean Society for Geospatial Information Science
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• v.11 no.1 s.24
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• pp.3-12
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• 2003

The main objective of this study is to extract the hydro-Parameter of the Tamjin River basin. A CIS is capable of extracting various hydrological factors from DEM. One of important tasks for hydrological analysis is the division of watershed. In this study, watershed itself and other geometric factors of watershed are extracted from DEM by using a CIS technique. The data of topographical map with scale of 1:25,000 and 1:250,000 in the Tamjin River basin is used for this study and it is converted to DEM date. Various forms of representation of spatial data are handled in main modules and a CRID module of ArcView. A GRID module is used on a stream in order to define watershed boundary. Based on the spatial analysis using those GIS technique, it would be possible to obtain the reasonable results of watershed characteristics. Also, the results show not only that GIS can aid watershed management, research and surveillance, but also that the geometric characteristics as parameters of watershed can be quantified more accurately and easily than conventional graphic methods. From the equations($Y=14632.87{\cdot}X^{-0.542444},\;Y=37014.1{\cdot}X^{-1.058808}$), it can be concluded that the optimal count of flow accumulation is 468 and cell size is 42m for spatial analysis by using GIS technique in Tamjin River basin.

• Journal of the Korean Geographical Society
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• v.48 no.3
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• pp.321-335
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• 2013

High resolution data for the coastal sand beach during short-term in Jinbok-ri, Uljin-gun, Gyeongsangbuk-do are obtained by terrestrial LiDAR. The micro-geomorphological changes of 8 times before and after the strong low-pressure events during June to September, 2009 and changes under the various environments of wave-energy are investigated in the study. The obvious geomorphological changes between the northern and southern sand beach in Jinbok-ri are revealed by terrestrial LiDAR as well as by grain size analysis. The strong waves by the typhoons decrease the area and volume of the beach, and especially the area is largely influenced. The erosive and depositional processes dominate the northern and southern sand beach, respectively, after high wave in September. These results suggest that lots of sand grains in the beach are largely re-transported within the beach rather than offshore.

• Journal of Cadastre & Land InformatiX
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• v.48 no.2
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• pp.21-30
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• 2018

The spatial information recently observed by various sensors and platforms has been provided by national portals through the establishment of a database over a number of time periods, with easy access to various types of information. Therefore, it is possible to analyze the changes in the national territory space according to time. This study is intend to analyze forest changes based on a case of some areas in Heongseong and Wonju using the various spatial information observed in many ways, such as aerial photographs, ortho photos, digital topographical maps, DEM and DSM. DSM created by the airborne lidar and the aerial photos was able to analyze forest change areas more effectively than DEM of topographical maps. Also, forest management and analysis could provide basic data for efficient preservation and management of forests using spatial information.

• The Journal of Engineering Geology
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• v.32 no.3
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• pp.411-420
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• 2022

Recently, research using remote sensing has been active in various fields such as environment, science, and society. The results of research using remote sensing are not only numerical results, but also play an important role in solving and preventing social and scientific problems. The purpose of this thesis is to tell the correlation between the data provided and each data by using remote sensing technology for the tidal flat environment. The purpose of this study is to obtain high-resolution data using artificial satellites during remote sensing to find out information on tidal flat currents. Tidal flats created by erosion, sedimentation, low tide, and high tide contain information about the tidal flat slope and information about the ecosystem. Therefore, it can be considered as one of the very important studies to analyze the overall tidal flow channel. This paper creates a DEM (Digital Elevation Model) through TanDEM-X, and DEM is used as the most basic data to create a tidal channel. The research area is a tidal flat located in the middle of the west coast of Ganghwado tidal flat. By analyzing the tidal channel created, various information such as the slope direction of Ganghwado tidal flat and the shape of the tidal channel can be grasped. It is expected that the results of this study will increase the importance and necessity of using DEM data for tidal flat research in the future, and that high-quality results can be obtained.