A washaway is a particular kind of landslide

Landslide

A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...

 that can affect man-made structures such as cutting

Cut (earthmoving)

In civil engineering, a cut or cutting is where soil or rock material from a hill or mountain is cut out to make way for a canal, road or railway line....

s, embankments

Embankment (transportation)

To keep a road or railway line straight or flat, and where the comparative cost or practicality of alternate solutions is prohibitive, the land over which the road or rail line will travel is built up to form an embankment. An embankment is therefore in some sense the opposite of a cutting, and...

 and bridge

Bridge

A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...

s. They are thus a hazard to railways and road traffic.

Overview

The biggest danger with washaways is that they may be difficult to spot in time to stop short of the point where one falls over the edge and/or into the water where one may drown.

Repairs

An embankment that is washed away can be repaired by restored by replacing the washed away earth, which is necessarily large because embankments have a gentle slope.

A quicker method is to replace the washed out earth with a criss-cross structure of timber steepers called a pigsty which is only slightly wider that the track itself. The pigsty has alternating layers of transverse and longitudinal layers of these sleepers, which contains a lot of air which saves weight. Steel and concrete sleepers are not necessarily suitable for this purpose as they are either not square or fragile.

The sleepers in the pigsty can be reused when the washaway is fully repaired. Rails can substitute for the sleepers. The hollow space inside the pigsty should be able to act as a culvert.

Warning devices

A mechanical railway signal that is normally "green" can be put to "red" if a link in the pulling wire is disengaged by a slump of the earth beneath.

An electrical railway signal that is normally green can be put to red if a contact is opened circuited by a slump of the earth beneath. One side of contact might be attached to the sleeper

Sleeper

A sleeper is a person who is sleeping. It may also refer to:-Music:* Sleeper , a Britpop band in the 1990s* The Sleepers , a punk/post-punk band active from 1978 until 1981...

s, while the other side is buried in the ballast beneath. To protect against a false feed keeping the warning signal green, the circuit should be double cut

Double switching

frame|right|A single-switched relay can close inadvertently in response to a single false feed current.frame|right|A double-switched relay cannot close inadvertently with the application of the same current...

 so that false feeds will connect positive to negative and blow a fuse, forcing the warning signal to red. A similar setup might be used to protect bridges likely to be hit by ship collisions, as with the 1993 Big Bayou Canot train wreck.

Accidents

Railway accidents involving bridge washaways include:
September 27, 1923 – near Glenrock, Wyoming

Glenrock, Wyoming

Glenrock is a town in Converse County, Wyoming, United States. The population was 2,231 at the 2000 census.Glenrock, known as Deer Creek Station, had its beginning as a mail and stage station along the Oregon Trail. The station served as a relay and eating place and was a vital supply point for...

 - a bridge over Coal Creek was washed away and a passenger train derailed, killing 30 of the train’s 66 passengers.
24 December 1953 - Tangiwai disaster

Tangiwai disaster

The Tangiwai disaster on 24 December 1953 was the worst rail accident in New Zealand history. An 11-carriage overnight express from Wellington to Auckland fell into the Whangaehu River at Tangiwai, ten kilometres west of Waiouru. The bridge carrying the North Island Main Trunk Railway over the...

 - lahar

Lahar

A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley. The term is a shortened version of "berlahar" which originated in the Javanese language of...

 caused bridge washaway; train thrown into river; 151 killed.
1974 - Crystal Brook

Crystal Brook

Crystal Brook may refer to:*Crystal Brook *Crystal Brook, South Australia, town...

, South Australia

South Australia

South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...

 - train thrown into river after washaway collapses bridge.
1993 - 114 perished in a passenger train that plunged into a river after floods washaway a bridge at Ngai Ndethya.
29 October 2005 - Veligonda train disaster

Veligonda train disaster

The Valigonda rail disaster occurred on 29 October 2005 near the town of Valigonda, south of Hyderabad in the Indian State of Andhra Pradesh. A flash flood swept away a small rail bridge, and a "Delta Express" train travelling on it derailed at the broken section of the line, killing at least 114...

- 114 killed