Berm
A berm is a level space, shelf, or raised barrier separating two areas. Berm is a loanword from Dutch.
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History
In mediaeval military engineering, a berm (or berme) was a level space between a parapet or defensive wall and an adjacent steep-walled ditch or moat. It was intended to reduce soil pressure on the walls of the excavated part to prevent its collapse. In the trench warfare of World War I, the name was applied to a similar feature at the lip of a trench, which served mainly as an elbow-rest for riflemen.
Modern usage
In modern military engineering, berm has come to mean the earthen or sod wall or parapet itself. The term especially refers to a low earthern wall adjacent to a ditch. The digging of the ditch (often by a bulldozer or combat engineering vehicle) can provide the soil from which the berm is constructed. Walls constructed in this manner are an effective obstacle to vehicles, including most armoured fighting vehicles, but are easily crossed by infantry. Because of the efficiency of construction, such walls can be made hundreds or thousands of kilometres long.
Berms are also used to control erosion and sedimentation by reducing the rate of Surface runoff. The berms either reduce the velocity of the water, or direct water to areas that are not susceptible to erosion, thereby reducing the adverse effects of running water on exposed top soil.
Uses in other applications
- In modern highway construction, a berm is a noise barrier constructed of earth, often landscaped, running along a highway to protect adjacent land users from noise pollution.
- In the natural building movement, berming refers to piling earth against an exterior wall to create thermal mass or reduce the visible footprint of an earth-sheltered home.
- In archeology, a berm is a narrow space, such as that between banks and ditches. It can also refer to a raised linear bank separating two areas.
- Regionally (especially Pennsylvania, Ohio, Indiana, and West Virginia) the word "berm" refers to the shoulder of a highway.
- In some regions a berm refers to a strip of grass that is located between a sidewalk and the curb of a street, also known as a tree lawn, "verge", or "parking strip".
- In Bicycle Motocross (BMX) bicycle racing, a berm refers to a banked turn made from dirt with a relatively tight radius.
- In coastal systems, a berm is a raised ridge of pebbles or sand found at high tide or storm tide marks on a beach.
See also
Categories
Dutch loanwords | Archaeological features | Civil engineering | Fortification