Terrain (), alternatively relief or topographical relief, is the dimension and shape of a given surface of a land. In physical geography, terrain is the lay of the land. This is usually expressed in terms of the elevation, slope, and orientation of terrain features. Terrain affects surface water flow and distribution. Over a large area, it can affect weather and climate patterns. Bathymetry is the study of underwater relief, while hypsometry studies terrain relative to sea level.
Importance
The understanding of terrain is critical for many reasons:
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The terrain of a region largely determines its suitability for human settlement: flatter tend to have better farming soils than steeper, rockier uplands.
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In terms of environmental quality, agriculture, hydrology and other interdisciplinary sciences;
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Understanding terrain also supports soil conservation, especially in agriculture. Contour ploughing is an established practice enabling sustainable agriculture on sloping land; it is the practice of ploughing along lines of equal elevation instead of up and down a slope.
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Terrain is military critical because it determines the ability of armed forces to take and hold areas, and move and material into and through areas. An understanding of terrain is basic to both defensive and offensive strategy. The military usage of "terrain" is very broad, encompassing not only landform but land use and land cover, surface transport infrastructure, built structures and human geography, and, by extension under the term human terrain, even psychological, cultural, or economic factors.
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Terrain is important in determining weather patterns. Two areas geographically close to each other may differ radically in precipitation levels or timing because of elevation differences or a rain shadow effect.
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Precise knowledge of terrain is vital in aviation, especially for low-flying routes and maneuvers (see terrain collision avoidance) and airport altitudes. Terrain will also affect range and performance of radars and terrestrial radio navigation systems. Furthermore, a hilly or mountainous terrain can strongly impact the implementation of a new aerodrome and the orientation of its runways.
Relief
Relief (or
local relief) refers specifically to the quantitative measurement of vertical elevation change in a
landscape. It is the difference between maximum and minimum elevations within a given area, usually of limited extent.
A relief can be described qualitatively, such as a "" or ""
plain or upland. The relief of a landscape can change with the size of the area over which it is measured, making the definition of the scale over which it is measured very important. Because it is related to the slope of surfaces within the area of interest and to the
Stream gradient of any streams present, the relief of a landscape is a useful metric in the study of the Earth's surface. Relief energy, which may be defined
inter alia as "the maximum height range in a regular grid",
is essentially an indication of the ruggedness or relative height of the terrain.
Geomorphology
Geomorphology is the long term study of the formation of terrain or topography.
Terrain is formed by concurrent processes operating on the underlying geological structures over geological time:
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Geology processes: migration of , faulting and folding, mountain formation, volcanic eruptions, etc.
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Erosional processes: glacial, water, wind, chemical and gravitational (mass wasting); such as , downhill creep, flows, slumps, and rock falls.
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Impact event: meteorite impact crater.
Tectonic processes such as Orogeny and Tectonic uplift cause land to be elevated, whereas erosional and weathering processes wear the land away by smoothing and reducing topographic features.[; ; ]
Land surface parameters are quantitative measures of various morphometric properties of a surface. The most common examples are used to derive slope or aspect of a terrain or curvatures at each location. These measures can also be used to derive Hydrology that reflect flow/erosion processes. Climate parameters are based on the modelling of solar radiation or air flow.
Land surface objects, or , are definite physical objects (lines, points, areas) that differ from the surrounding objects. The most typical examples airlines of Water divide, stream patterns, , Fall line, stream pool or borders of specific landforms.
Digital terrain model
See also
Bibliography
Further reading
External links
