Terrain
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:- The terrain of a region largely determines its suitability for human settlement: flatter alluvial plains tend to have better farming soils than steeper, rockier uplands.
- In terms of environmental quality, agriculture, hydrology and other interdisciplinary sciences; understanding the terrain of an area assists the understanding of watershed boundaries, drainage characteristics, drainage systems, groundwater systems, water movement, and impacts on water quality. Complex arrays of relief data are used as input parameters for hydrology transport models to allow prediction of river water quality.
- 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.
- Terrain is militarily critical because it determines the ability of armed forces to take and hold areas, and move troops 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.
- 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.
- Precise knowledge of terrain is vital in aviation, especially for low-flying routes and maneuvers 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
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:- Geological processes: migration of tectonic plates, faulting and folding, mountain formation, volcanic eruptions, etc.
- Erosional processes: glacial, water, wind, chemical and gravitational ; such as landslides, downhill creep, flows, slumps, and rock falls.
- Extraterrestrial: meteorite impacts.
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 hydrological parameters that reflect flow/erosion processes. Climatic parameters are based on the modelling of solar radiation or air flow.
Land surface objects, or landforms, are definite physical objects that differ from the surrounding objects. The most typical examples airlines of watersheds, stream patterns, ridges, break-lines, pools or borders of specific landforms.