A washout is the sudden

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

of soft

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

or other support surfaces by a gush of

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

, usually occurring during a heavy downpour of

rain Rain is a form of precipitation where water drop (liquid), droplets that have condensation, condensed from Water vapor#In Earth's atmosphere, atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is res ...

flash flood A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice and snow. Flash f ...

) or other

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...

flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

ing. These downpours may occur locally in a

thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorm ...

or over a large area, such as following the

landfall Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact ...

of a

tropical cyclone A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...

. If a washout occurs in a

crater A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...

-like formation, it is called a

sinkhole A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are also known as shakeholes, and to openings where surface water ...

, and it usually involves a leaking or broken

water main A water distribution system is a part of water supply network with components that carry potable water from a centralized treatment plant or wells to consumers to satisfy residential, commercial, industrial and fire fighting requirements. Defi ...

sewerage Sewerage (or sewage system) is the infrastructure that conveys sewage or surface runoff ( stormwater, meltwater, rainwater) using sewers. It encompasses components such as receiving drains, manholes, pumping stations, storm overflows, and scr ...

pipes. Other types of sinkholes, such as collapsed

cave Caves or caverns are natural voids under the Earth's Planetary surface, surface. Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance undergrou ...

s, are not washouts. Widespread washouts can occur in

mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher t ...

ous areas after heavy rains, even in normally dry

ravine A ravine is a landform that is narrower than a canyon and is often the product of streambank erosion. Ravines are typically classified as larger in scale than gullies, although smaller than valleys. Ravines may also be called a cleuch, dell, ...

s. A severe washout can become a

landslide Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...

, or cause a dam break in an earthen dam. Like other forms of erosion, most washouts can be prevented by

vegetation Vegetation is an assemblage of plants and the ground cover they provide. It is a general term, without specific reference to particular Taxon, taxa, life forms, structure, Spatial ecology, spatial extent, or any other specific Botany, botanic ...

whose

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

s hold the soil and/or slow the flow of surface and underground water.

Deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...

increases the risk of washouts.

Retaining wall Retaining walls are relatively rigid walls used for supporting soil laterally so that it can be retained at different levels on the two sides. Retaining walls are structures designed to restrain soil to a slope that it would not naturally keep to ...

s and

culvert A culvert is a structure that channels water past an obstacle or to a subterranean waterway. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe (fluid conveyance), pipe, reinforced concrete or other materia ...

s may be used to try to prevent washouts, although particularly severe washouts may even destroy these if they are not large or strong enough.

Effect on road and rail transport

In road and

rail transport Rail transport (also known as train transport) is a means of transport using wheeled vehicles running in railway track, tracks, which usually consist of two parallel steel railway track, rails. Rail transport is one of the two primary means of ...

, a washout is the result of a

natural disaster A natural disaster is the very harmful impact on a society or community brought by natural phenomenon or Hazard#Natural hazard, hazard. Some examples of natural hazards include avalanches, droughts, earthquakes, floods, heat waves, landslides ...

where the roadbed is eroded away by flowing water, usually as the result of a

.
Olympic National Forest (N.F.), Dosewallips Road Washout Project: Environmental Impact Statement
'. United States Forest Service, 2010. ii. When a washout destroys a railroad's right-of-way, the track is sometimes left suspended in midair across the newly formed gap, or it dips down into a ditch. This phenomenon is discussed in more detail under the term ''

''. Bridges may collapse due to

bridge scour Bridge scour is the removal of sediment such as sand and gravel from around bridge abutments or piers. Hydrodynamic scour, caused by fast flowing water, can carve out '' scour holes'', compromising the integrity of a structure. In the United ...

around one or more bridge

abutment An abutment is the substructure at the ends of a bridge span or dam supporting its superstructure. Single-span bridges have abutments at each end that provide vertical and lateral support for the span, as well as acting as retaining walls ...

s or piers. In 2004, the remnants of Hurricane Frances, and then Hurricane Ivan, caused a large number of washouts in western

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

and other parts of the southern

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

, closing some roads for days and parts of the

Blue Ridge Parkway The Blue Ridge Parkway is a National Parkway and National Scenic Byway, All-American Road in the United States, noted for its scenic beauty. The parkway, which is the longest linear park in the U.S., runs for through 29 counties in Virginia and ...

for months. Other washouts have also caused

train wreck A train accident or train wreck is a type of disaster involving one or more trains. Train wrecks often occur as a result of miscommunication, as when a moving train meets another train on the same track, when the wheels of train come off the ...

s where tracks have been unknowingly undermined.

Motorist Driving is the controlled operation and movement of a land vehicle, including cars, motorcycles, trucks, and buses. A driver's permission to drive on public highways is granted based on a set of conditions being met, and drivers are required to ...

s have also driven into flooded streams at night, unaware of a new washout on the road in front of them until it is too late to

brake A brake is a machine, mechanical device that inhibits motion by absorbing energy from a moving system. It is used for Acceleration, slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of ...

, sometimes prompting a high-water rescue. Major washouts can also ruin

pipeline A pipeline is a system of Pipe (fluid conveyance), pipes for long-distance transportation of a liquid or gas, typically to a market area for consumption. The latest data from 2014 gives a total of slightly less than of pipeline in 120 countries ...

s or undermine

utility pole A utility pole, commonly referred to as a transmission pole, telephone pole, telecommunication pole, power pole, hydro pole, telegraph pole, or telegraph post, is a column or post used to support overhead power lines and various other public util ...

s or underground lines, interrupting

public utilities A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and r ...

References

External links

{{Road types Flood Hydrology Water Weather hazards Road hazards

Effect on road and rail transport

See also

References

External links