Berm

For the berm in Western Sahara, seeMoroccan Western Sahara Wall.

"Burm" redirects here. For other uses, seeBurm (disambiguation).

Abermis a level space, shelf, or raised barrier (usually made ofcompacted soil) separating areas in a vertical way, especially partway up a long slope. It can serve as a terrace road, track, path, afortification line,aborder/separation barrierfor navigation, good drainage, industry, or other purposes.

Embankment damwith two berms

Etymology

The word is one ofMiddle Dutchand came into usage in English via French.

Military use

History

Inmedievalmilitary engineering,a berm (or berme) was a level space between aparapetordefensive walland an adjacent steep-walledditchormoat.It was intended to reducesoilpressureon the walls of the excavated part to prevent its collapse. It also meant that debris dislodged from fortifications would not fall into (and fill) a ditch ormoat.

In thetrench warfareofWorld War I,the name was applied to a similar feature at the lip of atrench,which served mainly as an elbow-rest forriflemen.

Modern usage

In modern military engineering, a berm is the earthen orsodwallor parapet, especially a low earthen wall adjacent to a ditch. The digging of the ditch (often by abulldozerormilitary engineering vehicle) can provide the soil from which the berm is constructed. Walls constructed in this manner are an obstacle tovehicles,including mostarmoured fighting vehiclesbut are easily crossed byinfantry.Because of the ease ofconstruction,such walls can be made hundreds or thousands of kilometres long. A prominent example of such a berm is the 2,700 km (1,700 mi)Moroccan Western Sahara Wall.

Erosion control

Berms are also used to control soilerosionandsedimentationby reducing the rate ofsurface runoff.The berms either reduce thevelocityof thewater,or direct water to areas that are not susceptible to erosion, thereby reducing the adverse effects of running water on exposedtopsoil.Following the 2010Deepwater Horizonoil spillin the Gulf of Mexico, the construction of berms designed to prevent oil from reaching the fragileLouisianawetlands(which would result in massive erosion) was proposed early on, and was officially approved by thefederal governmentin mid-June, 2010, after numerous failures to stop and contain the oil leak with more advanced technologies.

Geography

Main article:Berm (landform)

In coastal geography, abermis a bank of sand or gravel ridge parallel to the shoreline and a few tens of centimetres high, created by wave action throwing material beyond the average level of the sea.

House construction

Main article:Earth sheltering

Earth is piled up against exterior walls and packed, sloping down away from the house. The roof may or may not be fully earth covered, and windows/openings may occur on one or more sides of the shelter. Due to the building being above ground, fewer moisture problems are associated with earth berming in comparison to underground/fully recessed construction.

Other applications

A typical berm application

For general applications, a berm is a physical, stationary barrier of some kind. For example, inhighwayconstruction, a berm is anoise barrierconstructed of earth, oftenlandscaped,running along a highway to protect adjacent land users fromnoise pollution.The shoulder of a road is also called a berm and in New Zealand the word describes a publicly owned grassed nature strip sometimes planted with trees alongside urban roads (usually called a verge).[1]Insnowboard cross,a berm is a wall ofsnowbuilt up in a corner.Inmountain biking,a berm is a banked turn formed by soil, commonly dug from the track, being deposited on the outer rim of the turn. Incoastalsystems, a berm is a raised ridge ofpebblesorsandfound at hightideorstormtide marks on abeach.In snow removal, a berm orwindrowrefers to the linear accumulation of snow cast aside by aplow.Earth berms are used above particle accelerator tunnels to provide shielding from radiation.Inopen-pit mining,a berm refers to dirt androckpiled alongside ahaulage roador along the edge of a dump point. Intended as a safety measure, they are commonly required by government organizations to be at least half as tall as the wheels of the largestminingmachine on-site.

Physical security systems employ berms to exclude hostile vehicles and slow attackers on foot (similar to the military application without the trench). Security berms are common around military and nuclear facilities. An example is the berm proposed forVermont Yankee nuclear power plantin Vermont.AtBaylor Ballpark,a baseball stadium on the campus ofBaylor University,a berm is constructed down the right field line. The berm replaces bleachers, and general admission tickets are sold for fans who wish to sit on the grass or watch the game from the top of the hill.

Berms are also used as a method of environmental spill containment and liquid spill control.Bundingis the construction of a secondary impermeable barrier around and beneath storage or processing plant, sufficient to contain the plant's volume after a spill. This is often achieved on large sites by surrounding the plant with a berm. The USEnvironmental Protection Agency(EPA) requires that oils and fuels stored over certain volume levels be placed in secondary spill containment. Berms for spill containment are typically manufactured frompolyvinyl chloride(PVC) orgeomembranefabric that provide a barrier to keep spills from reaching the ground or navigable waterways. Most berms have sidewalls to keep liquids contained for future capture and safe disposal.

See also

• Road verge
• Earthworks (engineering)
• Bund
• Moroccan Wall
• Marches
• Limes (Roman Empire)
• Long acre
• Flood-meadow
• Floodplain

External links

Media related toBermsat Wikimedia Commons