Use Of Digital Terrain Model Research Articles

Relationships between topographically expressed zones of flow accumulation and sites of fault intersection: analysis by means of digital terrain modelling

Topographically expressed zones of flow accumulation often coincide with fault intersections because of increased rock fracturing. We have conducted a study of the interrelationships between topographically expressed accumulation zones and fault intersections, and the function of these sites in landscape evolution. The investigation has been performed with the use of digital terrain models, geological and soil data for the Crimean Peninsula. First, we carried out an analysis of associations of sites of fault intersections, intensive rock fracturing and abnormally high discharges of springs and boreholes, relating to fault intersections, with three types of landform element (zones of flow accumulation, transit and dissipation). We found that all phenomena under study are closely associated with topographically expressed accumulation zones. This has demonstrated that, within these zones, the soil moisture is influenced both by upward transport of deep-seated groundwater and by accumulation of overland lateral flows. Second, we predicted the effect of topography on irrigation-induced changes in the salt regime of soils and the groundwater level, assuming that topographically expressed accumulation zones can be marked by properties of fault intersections. We found that water leaking out of the North Crimean Canal can result in secondary salinisation of soils and a considerable rise of the watertable within some accumulation zones located downslope. Salts collected in the accumulation zones, and their slow movement through rock fractures, can lead to salinisation of the aquifers. We believe that topographically expressed accumulation zones are areas of contact and substance exchange between overland lateral and deep flows.

Digital terrain modelling of the surface and bed topography of the glacier austre okstindbreen, okstindan, norway

Twentieth‐century changes in Norwegian glaciers have been pronounced, but the different geometries and dynamics of the glaciers have caused different responses to similar climatic changes. Close to the Arctic Circle, all the glaciers of Svartisen, the largest ice‐covered area of northern Scandinavia, have retreated since the beginning of the century. However, several of the smaller glaciers which end at relatively high altitude have experienced both periods of advance and periods of retreat since the mid‐1960s. The mass balance of Engabreen, the largest of the West Svartisen glaciers, was positive in 21 of the 27 years to 1995–96. The sizes of most of the glaciers of the Okstindan area, 60 km south‐east of Svartisen, have also decreased throughout the twentieth century, but Corneliussens Bre, a small glacier at the eastern side of the massif, has been advancing since 1970. The areas supplying some of the southern glaciers of Okstindan have been reduced as a result of changes in ice thickness at high altitude. Studies of glacier change are aided by the use of digital terrain models (DTMs). Triangular irregular network DTMs of the surface and bed topography of the largest of the Okstindan glaciers, Austre Okstindbreen, have been used in studies of mass‐balance variations and changing surface flow patterns between 1976 and 1995.

Landslide Risk Mapping with use of DTM (Digital Terrain Model) and Remote Sensing Data

In this study, characteristics of landslide is considered from Remote Sensing data and DTM (Digital Terrain Model). A hill shading map, a sumit level map and a drinage pattern map were generated from DTM. A vegetation map and a landcover map were generated from LANDSAT TM as remote sensing data. From these maps, almost landslides were near an abundance of water resource which is stream or rice field. And landslide might be related with water erosion in topographical level.We suggest to use slope stability analysis for prediction of landslide. Generally, slope stability analysis has been applied to only the area where landslide had been occurred. However, we attempt to apply it to all areas regardless of landslide occurrence. A method of landslide risk mapping has been developed with use of Remote sensing data, DTM and ground survey data of geology and soil mechanics. The proposed method will be useful for preparedness of landslide prevention in the wide and steep terrain such as SHIKOKU Island, JAPAN where landslides occurred very often.

露天採掘に伴う景観変化の予測と評価

Landscape destruction after open-cut mining gives to the social impression. This paper presents the method to predict and evaluate landscape changes caused by open-cut mining. Landscape changes with the progression of mining are simulated by the use of digital terrain models, and that are shown on the computer graphic screen. Evaluation tests are conducted by using of photomontages composed of computer graphics and present appearance photographs. Two psychometrical evaluation methods, rating-scale method and selection method, are adopted to estimate the allowable scale of mined-out quarry from the viewpoint of landscape engineering.In this study, two quarries are chosen as the examples of case study. From the results of evaluation tests, it is shown that the landscape impact of mined-out quarry is subjected to the height ratio against the background mountains and the apprarent height of mining slope. Especially, the apparent height of mining slope is a important factor for landscape evaluation. It becomes clear that the allowable limit of the apparent height of mining slop is about 0.037. This value is equal to the visual angle of 1°, at which an ordinary person can distinguish the object observed. The apparent height 0.037 is therefore the quantitative criterion for the allowable scale of mined-out quarry from the viewpoint of landscape conservation.

Calculation of Maximum Snow-Avalanche Run-Out Distance by use of Digital Terrain Models

Digital maps and terrain models are used to calculate maximum snow-avalanche run-out distance based on topographic parameters. Maps of 1:50 000 scale are found to be accurate enough for the purpose. 113 well-known avalanches are discussed in this paper. A computer system is used to calculate terrain parameters such as rupture area (A), avalanche-path length (L), avalanche-track lengths (L1L2), and run-out lengths (L3). Maximum run-out angle (α), avalanche-track angle (β). and average angle of rupture zone (γ) are also found by computer. The use of computer and terrain model reduces subjective judgement of parameters to a minimum. Run-out distance was found to be best expressed by the regression equation:α = 0.91β + 0.08γ–3.5°. R2 = 0.94, S = 1.4°.L = 0.93L1 + 0.97L2 + 0.61A + 182 m. R2 = 0.96, S = 137 m.

Calculation of Maximum Snow-Avalanche Run-Out Distance by use of Digital Terrain Models

Digital maps and terrain models are used to calculate maximum snow-avalanche run-out distance based on topographic parameters. Maps of 1:50 000 scale are found to be accurate enough for the purpose. 113 well-known avalanches are discussed in this paper. A computer system is used to calculate terrain parameters such as rupture area (A), avalanche-path length (L), avalanche-track lengths (L 1 L 2), and run-out lengths (L 3). Maximum run-out angle (α), avalanche-track angle (β). and average angle of rupture zone (γ) are also found by computer. The use of computer and terrain model reduces subjective judgement of parameters to a minimum. Run-out distance was found to be best expressed by the regression equation: α = 0.91β + 0.08γ–3.5°. R 2 = 0.94, S = 1.4°. L = 0.93L 1 + 0.97L 2 + 0.61A + 182 m. R 2 = 0.96, S = 137 m.