Washout (erosion)

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Washout damage to Japan National Route 41 Damaged National Route 41 in Gero, Gifu, Japan.jpg
Washout damage to Japan National Route 41

A washout is the sudden erosion of soft soil or other support surfaces by a gush of water, usually occurring during a heavy downpour of rain (a flash flood) or other stream flooding. These downpours may occur locally in a thunderstorm or over a large area, such as following the landfall of a tropical cyclone. If a washout occurs in a crater-like formation, it is called a sinkhole, and it usually involves a leaking or broken water main or sewerage pipes. Other types of sinkholes, such as collapsed caves, are not washouts.

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Widespread washouts can occur in mountainous areas after heavy rains, even in normally dry ravines. A severe washout can become a landslide, or cause a dam break in an earthen dam. Like other forms of erosion, most washouts can be prevented by vegetation whose roots hold the soil and/or slow the flow of surface and underground water. Deforestation increases the risk of washouts. Retaining walls and culverts 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

A washout occurred on the Riverside and Great Northern Railway in Wisconsin Dells, Wisconsin, on June 11, 2004. Washout on the RGN.jpg
A washout occurred on the Riverside and Great Northern Railway in Wisconsin Dells, Wisconsin, on June 11, 2004.

In road and rail transport, a washout is the result of a natural disaster where the roadbed is eroded away by flowing water, usually as the result of a flood. [1] 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 erosion . Bridges may collapse due to bridge scour around one or more bridge abutments or piers.

In 2004, the remnants of Hurricane Frances, and then Hurricane Ivan, caused a large number of washouts in western North Carolina and other parts of the southern Appalachian Mountains, closing some roads for days and parts of the Blue Ridge Parkway for months. Other washouts have also caused train wrecks where tracks have been unknowingly undermined. Motorists 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, sometimes prompting a high-water rescue.

Major washouts can also ruin pipelines or undermine utility poles or underground lines, interrupting public utilities.

See also

Related Research Articles

<span class="mw-page-title-main">Erosion</span> Natural processes that remove soil and rock

Erosion is the action of surface processes that removes soil, rock, or dissolved material from one location on the Earth's crust and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as physical or mechanical erosion; this contrasts with chemical erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.

<span class="mw-page-title-main">Levee</span> Ridge or wall to hold back water

A levee, dike, dyke, embankment, floodbank, or stop bank is a structure used to keep the course of rivers from changing and to protect against flooding of the area adjoining the river or coast. It is usually earthen and often runs parallel to the course of a river in its floodplain or along low-lying coastlines.

<span class="mw-page-title-main">Flood</span> Water overflow submerging usually-dry land

A flood is an overflow of water 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 an area of study of the discipline hydrology and are of significant concern in agriculture, civil engineering and public health. Human changes to the environment often increase the intensity and frequency of flooding, for example land use changes such as deforestation and removal of wetlands, changes in waterway course or flood controls such as with levees, and larger environmental issues such as climate change and sea level rise. In particular climate change's increased rainfall and extreme weather events increases the severity of other causes for flooding, resulting in more intense floods and increased flood risk.

<span class="mw-page-title-main">Sinkhole</span> Geologically-formed topological depression

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 enters into underground passages known as ponor, swallow hole or swallet. A cenote is a type of sinkhole that exposes groundwater underneath. Sink and stream sink are more general terms for sites that drain surface water, possibly by infiltration into sediment or crumbled rock.

<span class="mw-page-title-main">Stormwater</span> Water that originates during precipitation events and snow/ice melt

Stormwater, also written storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil (infiltrate) and become groundwater, be stored on depressed land surface in ponds and puddles, evaporate back into the atmosphere, or contribute to surface runoff. Most runoff is conveyed directly as surface water to nearby streams, rivers or other large water bodies without treatment.

<span class="mw-page-title-main">Flash flood</span> Rapid flooding of geomorphic low-lying areas

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 or snow flowing over ice sheets or snowfields. Flash floods may also occur after the collapse of a natural ice or debris dam, or a human structure such as a man-made dam, as occurred before the Johnstown Flood of 1889. Flash floods are distinguished from regular floods by having a timescale of fewer than six hours between rainfall and the onset of flooding.

<span class="mw-page-title-main">Stream bed</span> Channel bottom of a stream, river, or creek

A stream bed or streambed is the bottom of a stream or river (bathymetry) or the physical confine of the normal water flow (channel). The lateral confines or channel margins are known as the stream banks or river banks, during all but flood stage. Under certain conditions a river can branch from one stream bed to multiple stream beds. A flood occurs when a stream overflows its banks and flows onto its flood plain. As a general rule, the bed is the part of the channel up to the normal water line, and the banks are that part above the normal water line. However, because water flow varies, this differentiation is subject to local interpretation. Usually, the bed is kept clear of terrestrial vegetation, whereas the banks are subjected to water flow only during unusual or perhaps infrequent high water stages and therefore might support vegetation some or much of the time.

<span class="mw-page-title-main">Geological hazard</span> Geological state that may lead to widespread damage or risk

A geologic hazard or geohazard is an adverse of geologic condition capable of causing widespread damage or loss of property and life. These hazards are geological and environmental conditions and involve long-term or short-term geological processes. Geohazards can be relatively small features, but they can also attain huge dimensions and affect local and regional socio-economics to a large extent.

<span class="mw-page-title-main">Culvert</span> Structure to channel water past an obstacle

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, reinforced concrete or other material. In the United Kingdom, the word can also be used for a longer artificially buried watercourse.

<span class="mw-page-title-main">Hurricane Bertha (1996)</span> Category 3 Atlantic hurricane in 1996

Hurricane Bertha was an intense and early-forming major hurricane that affected areas from the Leeward Islands to the United States in July of the 1996 Atlantic hurricane season. The second named storm, first hurricane, and first major hurricane during the season, Bertha originated from a tropical wave that moved off the coast of Africa in early July. Steadily organizing while moving generally towards the west, the disturbance was designated as a tropical depression at 0000 UTC on July 5, and was further upgraded to a tropical storm by 1200 UTC later that day. Over the next few days, continued intensification occurred, and Bertha became a Category 1 hurricane on the Saffir-Simpson hurricane scale, the first hurricane of the season, prior to moving through the northern Leeward Islands. Late on July 8, a period of rapid intensification began, and at 0600 UTC on July 9, Bertha reached its peak intensity with maximum sustained winds of 115 mph (185 km/h) with a minimum barometric pressure of 960 mbar (28 inHg). Moving around the western periphery of the subtropical ridge, Bertha passed north of the Bahamas as a weakening hurricane before turning towards the north-northeast and undergoing another period of rapid intensification. Late on July 12, Bertha made landfall between Wrightsville Beach and Topsail Beach, North Carolina with winds of 105 mph (169 km/h). Gradual weakening ensued the following day as Bertha moved up the Mid-Atlantic and into New England before becoming an extratropical cyclone on July 14. The storm's remnants persisted for another several days, before dissipating on July 18.

<span class="mw-page-title-main">Levee breach</span> Situation where a levee containing water is breached

A levee breach or levee failure is a situation where a levee fails or is intentionally breached, causing the previously contained water to flood the land behind the levee.

<span class="mw-page-title-main">Flash flood warning</span> Weather warning indicating observed or imminent flash flooding in the warned area

A flash flood warning is a severe weather warning product of the National Weather Service that is issued by national weather forecasting agencies throughout the world to alert the public that a flash flood is imminent or occurring in the warned area. A flash flood is a sudden, violent flood after a heavy rain, or occasionally after a dam break. Rainfall intensity and duration, topography, soil conditions, and ground cover contribute to flash flooding.

Internal erosion is the formation of voids within a soil caused by the removal of material by seepage. It is the second most common cause of failure in levees and one of the leading causes of failures in earth dams, responsible for about half of embankment dam failures.

There have been known various classifications of landslides. Broad definitions include forms of mass movement that narrower definitions exclude. For example, the McGraw-Hill Encyclopedia of Science and Technology distinguishes the following types of landslides:

<span class="mw-page-title-main">Severe weather</span> Any dangerous meteorological phenomenon

Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atmospheric conditions. High winds, hail, excessive precipitation, and wildfires are forms and effects of severe weather, as are thunderstorms, downbursts, tornadoes, waterspouts, tropical cyclones, and extratropical cyclones. Regional and seasonal severe weather phenomena include blizzards (snowstorms), ice storms, and duststorms.

<span class="mw-page-title-main">Drop structure</span> Structure that lowers elevation of water in a controlled fashion

A drop structure, also known as a grade control, sill, or weir, is a manmade structure, typically small and built on minor streams, or as part of a dam's spillway, to pass water to a lower elevation while controlling the energy and velocity of the water as it passes over. Unlike most dams, drop structures are usually not built for water impoundment, diversion or raising the water level. Mostly built on watercourses with steep gradients, they serve other purposes such as water oxygenation and erosion prevention.

<span class="mw-page-title-main">Bridge scour</span> Removal of sediment from around bridge abutments or piers by the movement of water

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.

<span class="mw-page-title-main">Schoharie Creek Bridge collapse</span> 1987 bridge collapse in Montgomery County, New York

The Schoharie Creek Bridge was a New York State Thruway (I-90) bridge over the Schoharie Creek near Fort Hunter and the Mohawk River in New York State. On April 5, 1987, it collapsed due to bridge scour at the foundations after a record rainfall. The collapse killed ten people. The replacement bridge was completed and fully open to traffic on May 21, 1988.

<span class="mw-page-title-main">San Rafael Falls</span> Waterfall on the Coca River in Ecuador

San Rafael Falls was a waterfall on the Coca River in Sucumbíos and Napo, Ecuador. Standing 131 metres (430 ft) high, it was the tallest and most powerful waterfall in Ecuador and a popular tourist attraction. The falls were located at the eastern boundary of Cayambe Coca National Park, in the eastern Andean foothills about 170 kilometres (110 mi) to the east of Quito.

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