Terrain (from Latinterra'earth'), alternativelyrelief ortopographicalrelief, is thedimension and shape of a given surface of aland. Inphysical geography, terrain is the lay of the land. This is usually expressed in terms of theelevation,slope, and orientation of terrain features. Terrain affects surface water flow and distribution. Over a large area, it can affectweather andclimate patterns.Bathymetry is the study of underwater relief, whilehypsometry studies terrain relative tosea level.
The understanding of terrain is critical for many reasons:
The terrain of a region largely determines its suitability for human settlement: flatteralluvial plains tend to have better farming soils than steeper, rockier uplands.[1]
Understanding terrain also supportssoil conservation, especially in agriculture.Contour ploughing is an established practice enablingsustainable agriculture on sloping land; it is the practice of ploughing along lines of equal elevation instead of up and down a slope.
Terrain ismilitarily critical because it determines the ability of armed forces to take and hold areas, and movetroops and material into and through areas. Anunderstanding 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 andhuman geography, and, by extension under the termhuman terrain, even psychological, cultural, or economic factors.[4]
Terrain is important in determiningweather patterns. Two areas geographically close to each other may differ radically inprecipitation levels or timing because of elevation differences or arain shadow effect.
Precise knowledge of terrain is vital inaviation, especially for low-flying routes and maneuvers (see terrain collision avoidance) and airport altitudes. Terrain will also affect range and performance of radars and terrestrialradio navigation systems. Furthermore, a hilly or mountainous terrain can strongly impact the implementation of a newaerodrome and the orientation of its runways.
Relief (orlocal relief) refers specifically to the quantitative measurement of vertical elevation change in alandscape. It is the difference between maximum and minimum elevations within a given area, usually of limited extent.[5] A relief can be described qualitatively, such as a "low relief" or "high relief"plain orupland. 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 thegradient 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 definedinter alia as "the maximum height range in a regular grid",[6] is essentially an indication of the ruggedness or relative height of the terrain.
Geomorphology is the long term study of the formation of terrain or topography.[7] Terrain is formed by concurrent processes operating on the underlyinggeological structures overgeological time:
Tectonic processes such asorogenies anduplifts cause land to be elevated, whereas erosional andweathering processes wear the land away by smoothing and reducing topographic features.[8] The relationship oferosion and tectonics rarely (if ever) reaches equilibrium.[9][10][11] These processes are also codependent, however the full range of their interactions is still a topic of debate.[12][13][14]
Land surface parameters are quantitative measures of variousmorphometric properties of a surface. The most common examples are used to deriveslope oraspect of a terrain or curvatures at each location. These measures can also be used to derivehydrological parameters that reflect flow/erosion processes.Climatic parameters are based on the modelling ofsolar radiation or air flow.
Land surface objects, orlandforms, are definite physical objects (lines, points, areas) that differ from the surrounding objects. The most typical examples airlines ofwatersheds,stream patterns,ridges,break-lines,pools or borders of specific landforms.
^Baker, N.T.; Capel, P.D. (2011). "Environmental factors that influence the location of crop agriculture in the conterminous United States".U.S. Geological Survey Scientific Investigations Report 2011–5108.U.S. Geological Survey. p. 72.
^"Joint Publication 1-02"(PDF).Department of Defense Dictionary of Military and Associated Terms.* "compartmentation ... [involves] areas bounded on at least two sides by terrain features such as woods..." * "culture — A feature of the terrain that has been constructed by man. Included are such items as roads, buildings, and canals; boundary lines; and, in a broad sense, all names and legends on a map." * "key terrain — Any locality, or area, the seizure or retention of which affords a marked advantage to either combatant." * "terrain intelligence — Intelligence on the military significance of natural and manmade characteristics of an area."
^Gasparini, N.; Bras, R.; Whipple, K. (2006). "Numerical modeling of non–steady-state river profile evolution using a sediment-flux-dependent incision model. Special Paper".Geological Society of America.398:127–141.doi:10.1130/2006.2398(08).
^Roe, G.; Stolar, D.; Willett, S. (2006). "Response of a steady-state critical wedge orogen to changes in climate and tectonic forcing. Special Paper".Geological Society of America.398:227–239.doi:10.1130/2005.2398(13).
^Wobus, C.; Whipple, K.; Kirby, E.; Snyder, N.; Johnson, J.; Spyropolou, K.; Sheehan, D. (2006). "Tectonics from topography: Procedures, promise, and pitfalls. Special Paper".Geological Society of America.398:55–74.doi:10.1130/2006.2398(04).
Hoth, S.; Adam, J.; Kukowski, N.; Oncken, O. (2006). "Influence of erosion on the kinematics of bivergent orogens: Results from scaled sandbox simulations. Special Paper".Geological Society of America.398:201–225.doi:10.1130/2006.2398(12).
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