• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.6D
• /
• pp.1019-1023
• /
• 2006

The slope information based on DEM is very useful for urban planning, landscape, road design and water resource areas such as rainfall-runoff and soil erosion estimation. The resolution of slope, which is from DEM, can be variously decided by an application fields and the kinds of modeling method. In particular, the more decreased resolution makes the more decreased slope value because of the increased horizontal distance. This study presents slope evaluation method by aggregation method based on discharge and Manning's velocity equation to advance the loss of slope information in according to the resolution, and then applied it to calculate topographic factors of soil erosion model. As a result, conventional method shows 34.8% errors but aggregation method shows 12.6% errors. This study selected up-, middle-, and downstream region in watershed and analyzed the capability of aggregation method in order to estimate the influence of topographic characteristics. As a result of estimation, aggregation method shows more advanced results than conventional method. Therefore, the slope evaluation method by aggregation method can improve efficiently the loss of slope information in according to the variation of resolution in water resource area such as rainfall-runoff model.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.3
• /
• pp.379-386
• /
• 2007

In this paper, topographic factors over 3-dimensional hills were estimated through wind tunnel tests. Topographic models having five different slopes of $5.71^{\circ}, \;11.31^{\circ},\;16.70^{\circ},\;21.80^{\circ}$, and $26.57^{\circ}$ which were based on Korean Building Code(KBC(2005), were made for wind tunnel tests. From the result of wind tunnel tests, topographic factors over 3-dimensional hills were obtained at various locations, and the ranges of topographic effects were decided. The ranges of topographic effects was whole area of the hills in the horizontal ranges and heights of 3.5 times of the hills in the vortical ranges. Topographic effects was large at the top of hills, and wind velocity was increased 57% over hill of $5.71^{\circ}$, 75% over hill of $11.31^{\circ}$, 79% over hill of $16.70^{\circ}$, 81% over hill of $21.80^{\circ}$, and 61% over hill of $26.57^{\circ}$. Wind velocity was bigger over surface of across-wind direction of hills than one over surface of wind direction of hills, and wind velocity was increased $10{\sim}30%$ at locations of across-wind direction.

• Journal of Wetlands Research
• /
• v.11 no.2
• /
• pp.89-98
• /
• 2009

This study determines the stream mean slope, stream slope and longitudinal stream profile based on the concept of informational entropy. Maximizing the entropy will make the probability distribution of longitudinal stream profile as uniform as possible while satisfying the constraints. Using this relationships the mean stream slope, stream slope and longitudinal stream profile formulas were derived. The parameters of the applied streams were estimated by the least square method using the geomorphological factors of Dalchon stream basin obtained from Chungcheong Buk-Do local stream consolidation scheme drawings. The comparative investigation was performed between the observed and simulated mean stream slope and longitudinal stream profile, and are in good agreement with the measured data. It is noted that this results can be used in the estimation of stream mean slope and longitudinal stream profile.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.1B
• /
• pp.1-11
• /
• 2011

Channel network delineation from DEM (Digital Elevation Model) is a fundamental pre-process for hydrologic model application since it determines the drainage system in a watershed. This study aims to propose an effective and efficient channel network delineation process and assess the effects of DEM-based channel networks on the watershed drainage system. For these objectives, we applied two methods to generate the channel networks of the Jinan-cheon catchment with $18.28km^2$ from the 20 m resolution DEM: a widely-used area-threshold method and a slope-area threshold method based on the relationship between contributing areas and local slopes. The results showed that the area-threshold method led to unreliable drainage system, which did not satisfy geomorphological laws with respect to drainage density and source area representation whereas the slope-area threshold method provided acceptable results under the geomorphological laws. Our suggestions in this study can give valuable pre-processing information in DEM-based hydrologic modeling.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.15 no.2
• /
• pp.221-230
• /
• 1997

In hydrology analysis, the result of a slope analysis for terrain have an very important effect on water quality and water quantity Recently, a slope analysis tend to use the digital elevation model rater than the traditional map sheet. But a terrain slope analysis by the digital elevation model depends on grid size of the digital elevation model. Hence the effect of a slope analysis by the digital elevation model is a important factor. In this study, therefor, in order to determine a hydrological parameter and a terrain parameter for simulation of the water quality and the hydrological property, we adapted two sample area that are the Nerin stream of the basin of the Soyang lake and a Osip stream of Samchuk, and its individual coverages are $640\;km^2$ and $33\;km^2$. Also to analyze the effect of grid size in the slope of a basin, we apply DEM changing a grid size respectively at intervals of 100 m from 100 m to 1.000m for the Nerin stream basin and at intervals of 10 m from 20 m to 300 m for the Osip stream basin.

• Journal of the Korean GEO-environmental Society
• /
• v.9 no.5
• /
• pp.61-69
• /
• 2008

In general, it has been usually used the method that assess rock slope stability using stereographic projection method, limit equilibrium analysis, numerical analysis and slope stability evaluation table. Several methods for assessing the stability of rock slopes has been proposed on the basis of site investigation data. These method adopted different evaluation items and weighting factors by researchers, organization and nation. But the researches for each evaluation items were insufficient. So the effectiveness of rock slope stability evaluation items for geometrical configuration (slope height, slope direction and angle, dip and dip direction of major discontinuity, absolute value for the direction difference for slope and major discontinuities) and topographical characteristic (possibility of topographical water concentration, upper natural slope angle, slope configuration) using 315 failure and stable highway rock slope analysis data, AV (abnormal value) analysis and NMAV (normalized maximum abnormal value) analysis were evaluated.

• Journal of The Geomorphological Association of Korea
• /
• v.21 no.4
• /
• pp.85-96
• /
• 2014

A waterfall is a channel unit with steep bedrock. No strict criteria for height, water volume, gradient to define waterfalls exist in Korea. The goal of our study is to classify waterfalls based on morphological forms which are the outcomes of developmental processes. The genesis of waterfall depends upon erosional properties of waterfall. The height, gradient, bedrock strength and stream power of waterfalls are regarded as the main factors, by which waterfalls can be classified. We find out that the most important factor for the development of waterfalls is joint system. Development of joint system varies depending on bedrocks. Flow directions and erosional types are decided by the density and direction of joint system in the bedrock, which also decide the height and gradient of stream bed. Joint type decides the gradients of the bed, gradient and height of waterfalls, therefore, decides morphological forms.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.32 no.1
• /
• pp.55-62
• /
• 2014

In this study, we investigated the landslides area which occurred in Umyeonsan in 2011 and collected landslide location data. Using this field data with aerial photos and LiDAR data which is obtained before and after disaster event, we analyzed the landslide occurrence frequency per unit area about various topographic characteristics. In case of slope, we compared two kind of slopes which are calculated with Neighborhood algorithm and maximum slope algorithm. Also we used aspect, elevation, profile curvature and planform curvature in topographic analysis of landslide occurrence locations. As a result, the region of which maximum slope is $40^{\circ}-45^{\circ}$ is relatively hazardous in landslide. If the perpendicular surface to the direction of the maximum slope is concave, it is more hazardous than other case.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 2003.08a
• /
• pp.63-70
• /
• 2003

Berkhoff(1972)는 해저 경사가 완만한 지형에서의 파랑 변형을 계산하는 완경사 방정식을 제안하였다. 이 방정식은 수식이 매우 간단하면서도 비교적 정확하게 파랑을 예측할 수 있어 현재까지도 해안공학 전반에 걸쳐 많이 적용되고 있다. 그러나 Berkhoff(1972)의 완경사 방정식은 계산이 비교적 번거로워 현재는 계산하기 편리한 포물형 완경사 방정식(Radder,1979) 또는 쌍곡선형 완경사 방정식(Copeland,1985) 등의 근사 모델을 사용하고 있다. 하지만, 이러한 근사모델은 지배방정식을 유도할 때 생기는 가정들에 의해 실제현장 적용성과 해의 정확성에는 언제나 일정한 한계가 있다. (중략)

• Spatial Information Research
• /
• v.16 no.3
• /
• pp.359-372
• /
• 2008

This research estimated Pinus densiflora distribution and suggested an optimal grid size of DEM for ecologically better explaining spatial distribution and appearance pattern of Pinus densiflora and analyze appearance frequency of Pinus densiflora by topographical factors. And this work ultimately aimed at topographically analyzing spatial distribution of Pinus densiflora by comparing impact of topographical factors. The aspect was analyzed in detail, east, west, south, north, from DEM with 1m grid size, and simply, east, west, south or east, south from DEM with bigger grid size. As a result of distribution of Pinus densiflora by aspect, Pinus densiflora appeared in all aspect with smaller grid size, while distribution in specific aspect decreased with bigger grid size. The analysis of appearance frequency with 100m grid size represented spatial distribution characteristics of Pinus densiflora as visual interpretation showed. The results of comparing impact of aspect, slope, TWI proved that aspect have more impact on distribution of Pinus densiflora than slope and there was not enough a difference between impact of slope and TWI.