Mudflow
Encyclopedia
A mudslide is the most rapid (up to 80 km/h, or 50 mph) and fluid type of downhill mass wasting
. It is a rapid movement of a large mass of mud
formed from loose soil
and water
. Similar terms are mudflow, mud stream, debris flow
(e.g. in high mountain
s), jökulhlaup
, and lahar
(from volcanoes, see also pyroclastic flow
).
However, these terms show a broad variety
Heavy rainfall, snow
melt, or high levels of ground water flowing through cracked bedrock may trigger a movement of soil or sediments. Flood
s, debris- and mud flows may also occur when strong rains on hill
or mountain slopes cause extensive erosion
and/or what is known as "channel scour". The 2006 Sidoarjo mud flow
may have been caused by rogue drilling.
Some broad mudflows are rather viscous and therefore slow; others begin very quickly and continue like an avalanche
. If large enough they can devastate villages and countrysides. They are composed of at least 50% silt and clay-sized materials and up to 30% water. Mudflows are common even in the hill
s around Los Angeles
where they have destroyed many homes built on hillsides without sufficient support.
The point where a muddy material begins to flow depends on its grain
and the water content. Fine grainy material or soil has a smaller friction angle than a coarse sediment
or a debris
flow, but falling rock pieces can trigger a material flow, too.
On December 14, 1999 in Vargas, Venezuela
, a mudslide known as The Vargas tragedy, which significantly altered more than 60 kilometers (37 mi) of its coastline, was triggered due to heavy rainfall and caused estimated damages of USD $1.79 to $3.5 billion, a death toll considered to be between 10,000 and 30,000, 85,000 people evacuate
d and led to the complete collapse of the state's infrastructure.
Mudslides are caused by unusually heavy rain or a sudden thaw. They consist mainly of mud and water plus fragments of rock and other debris, this causes them to behave like a flood. They can move houses off their foundations or bury a place within minutes, this is due to their incredibly strong currents.
Every year combined they kill more people than typhoons, hurricanes and cyclones do. They are rarely given media coverage and are not recognised as much as they should be for their fatalities.
Jan. 1: Heavy rain triggered two mudslides on the Ilha Grande resort near the Brazilian city of Rio de Janeiro
. A luxury hotel was swept away, killing at least 30 people.
March 1: Ninety-four bodies were found and 320 people were reported missing after a mudslide spawned by torrential rains in the district of Bududa
in eastern Uganda engulfed three villages.
April 5: Floods and mudslides in the Brazilian state of Rio de Janeiro
killed at least 212 and injured 161. More than 100 were reported missing.
June 15: Powerful landslides triggered by heavy rains killed at least 48 people and left dozens of others missing in southeastern Bangladesh
.
June 17: Torrential rains triggered mudslides on the border area between western Myanmar
and Bangladesh
, killing at least 46 people.
June 21: Floods and landslides in northeastern Brazil
killed at least 44 people, leaving more than 1,000 missing.
Aug. 6: Abrupt torrential rains triggered mudslides in India-controlled Kashmir's Leh region, killing at least 166 people. Another 400 were reported missing.
Aug. 7: At least 63 people were killed in landslides and mudslides in northern Pakistan
.
Aug. 8: Massive rain-triggered mudslides hit Zhouqu county of Gansu province in northwestern China
, killing at least 1,467 people and left 298 others missing until Aug. 30.
Sept. 2-5: Three days of torrential rains set off scores of landslides across Guatemala
, killing at least 45 civilians and rescuers, affecting some 50,000 people and causing an economic loss of 375 million to 500 million U.S.dollars.
Sept. 28-29: Torrential rains triggered floods and mudslides in Oaxaca state and Chiapas state in southern Mexico
, causing at least 33 deaths.
, a volcano in the Cascade Mountain Range in the State of Washington, USA. The volume of material was 2.8 km³. Directly in the path of the huge mudslide was Spirit Lake. Normally a chilly 5°C, the mudslide instantly raised the temperature to near 38°C. Today the bottom of Spirit Lake is 100 feet above the original surface. The lake now has two and a half times more surface area than it did before the eruption.
However, the world's largest prehistoric landslide, discovered to date, took place in south-western Iran
, and is named the Saidmarreh Landslide. The landslide was located on the Kabir Kuh anticline in Southwest Iran
at 33 degrees N, 47.65 degrees E. The landslide had a volume of about 20 cubic kilometers, a depth of 300 m, a travel distance of 14 km and a width of 5 km. This means that about 50 billion tons of rock moved in this single event alone.
During intense rainfall or storms, listen to weather warnings on the radio, look for tilted trees or posts, and listen for rumbling sounds which might indicate that a landslide or mudslide is approaching. If you see a small trickle of mud in a wash, creek or stream, move away from the area as quickly as possible; it may be a warning sign that a larger flow is imminent. Finally, if you do see a mudslide approaching, you should get to high ground out of its path as quickly as possible. If you see rocks or other debris approaching your position, find shelter and take cover, if possible under a piece of heavy furniture such as a desk or table.
After a mudslide has occurred, check for injured or trapped people, but try to avoid entering the mudslide's path. Listen for emergency instructions on the radio or TV. If you see that utility lines or cables in the area are broken, report them to the proper authorities as soon as possible.
Mass wasting
Mass wasting, also known as slope movement or mass movement, is the geomorphic process by which soil, regolith, and rock move downslope under the force of gravity. Types of mass wasting include creep, slides, flows, topples, and falls, each with its own characteristic features, and taking place...
. It is a rapid movement of a large mass of mud
Mud
Mud is a mixture of water and some combination of soil, silt, and clay. Ancient mud deposits harden over geological time to form sedimentary rock such as shale or mudstone . When geological deposits of mud are formed in estuaries the resultant layers are termed bay muds...
formed from loose soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
and water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
. Similar terms are mudflow, mud stream, debris flow
Debris flow
A debris flow is a fast moving, liquefied landslide of unconsolidated, saturated debris that looks like flowing concrete. It is differentiated from a mudflow in terms of the viscosity and textural properties of the flow. Flows can carry material ranging in size from clay to boulders, and may...
(e.g. in high mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...
s), jökulhlaup
Jökulhlaup
A jökulhlaup is a glacial outburst flood. It is an Icelandic term that has been adopted by the English language. It originally referred to the well-known subglacial outburst floods from Vatnajökull, Iceland which are triggered by geothermal heating and occasionally by a volcanic subglacial...
, and 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...
(from volcanoes, see also pyroclastic flow
Pyroclastic flow
A pyroclastic flow is a fast-moving current of superheated gas and rock , which reaches speeds moving away from a volcano of up to 700 km/h . The flows normally hug the ground and travel downhill, or spread laterally under gravity...
).
- in water contentWater contentWater content or moisture content is the quantity of water contained in a material, such as soil , rock, ceramics, fruit, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from 0 to the value of the materials' porosity at...
(from loamy mud, to almost liquid, and even steam), - in material (wet soil, sandSandSand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
y sedimentSedimentSediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s and/or siltSiltSilt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
, dirtDirtDirt is unclean matter, especially when in contact with a person's clothes, skin or possessions when they are said to become dirty. Common types of dirt include:* dust — a general powder of organic or mineral matter...
, rockRock (geology)In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
, debrisDebrisDebris is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, in geology, large rock fragments left by a melting glacier etc. The singular form of debris is debris...
, volcanic ashLaharA 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...
, small plants, and even trees) - in lengthLengthIn geometric measurements, length most commonly refers to the longest dimension of an object.In certain contexts, the term "length" is reserved for a certain dimension of an object along which the length is measured. For example it is possible to cut a length of a wire which is shorter than wire...
, total massMassMass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
, and velocityVelocityIn physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
Triggering of Mudslides
Snow
Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...
melt, or high levels of ground water flowing through cracked bedrock may trigger a movement of soil or sediments. Flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
s, debris- and mud flows may also occur when strong rains on hill
Hill
A hill is a landform that extends above the surrounding terrain. Hills often have a distinct summit, although in areas with scarp/dip topography a hill may refer to a particular section of flat terrain without a massive summit A hill is a landform that extends above the surrounding terrain. Hills...
or mountain slopes cause extensive erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
and/or what is known as "channel scour". The 2006 Sidoarjo mud flow
Sidoarjo mud flow
The Sidoarjo mud flow or Lapindo mud, also informally abbreviated as Lusi, a contraction of Lumpur Sidoarjo , is a mud volcano in the subdistrict of Porong, Sidoarjo in East Java, Indonesia that has been in eruption since May 2006...
may have been caused by rogue drilling.
Some broad mudflows are rather viscous and therefore slow; others begin very quickly and continue like an avalanche
Avalanche
An avalanche is a sudden rapid flow of snow down a slope, occurring when either natural triggers or human activity causes a critical escalating transition from the slow equilibrium evolution of the snow pack. Typically occurring in mountainous terrain, an avalanche can mix air and water with the...
. If large enough they can devastate villages and countrysides. They are composed of at least 50% silt and clay-sized materials and up to 30% water. Mudflows are common even in the hill
Hill
A hill is a landform that extends above the surrounding terrain. Hills often have a distinct summit, although in areas with scarp/dip topography a hill may refer to a particular section of flat terrain without a massive summit A hill is a landform that extends above the surrounding terrain. Hills...
s around Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
where they have destroyed many homes built on hillsides without sufficient support.
The point where a muddy material begins to flow depends on its grain
GRAIN
GRAIN is a small international non-profit organisation that works to support small farmers and social movements in their struggles for community-controlled and biodiversity-based food systems. Our support takes the form of independent research and analysis, networking at local, regional and...
and the water content. Fine grainy material or soil has a smaller friction angle than a coarse sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
or a debris
Debris
Debris is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, in geology, large rock fragments left by a melting glacier etc. The singular form of debris is debris...
flow, but falling rock pieces can trigger a material flow, too.
On December 14, 1999 in Vargas, Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
, a mudslide known as The Vargas tragedy, which significantly altered more than 60 kilometers (37 mi) of its coastline, was triggered due to heavy rainfall and caused estimated damages of USD $1.79 to $3.5 billion, a death toll considered to be between 10,000 and 30,000, 85,000 people evacuate
Emergency evacuation
Emergency evacuation is the immediate and rapid movement of people away from the threat or actual occurrence of a hazard. Examples range from the small scale evacuation of a building due to a bomb threat or fire to the large scale evacuation of a district because of a flood, bombardment or...
d and led to the complete collapse of the state's infrastructure.
Mudslides and Landslides
Landslide is a general term referring to all types of surface movement particularly avalanches involving the mass movement downhill of soil, rock or snow under the action of gravity. Landslides and avalanches can be devastating in terms of human life and general destruction.Mudslides are caused by unusually heavy rain or a sudden thaw. They consist mainly of mud and water plus fragments of rock and other debris, this causes them to behave like a flood. They can move houses off their foundations or bury a place within minutes, this is due to their incredibly strong currents.
Every year combined they kill more people than typhoons, hurricanes and cyclones do. They are rarely given media coverage and are not recognised as much as they should be for their fatalities.
Mudslide Geography
When a mudslide occurs it is given four named areas, the 'main scarp', in bigger mudslides the 'upper and lower shelves' and the 'toe'. The main scarp will be the original area of incidence, the toe is the last affected area(s). The upper and lower shelves are located wherever a large dip (due to mountain or natural drop) in in the mudslides path. Due to this a mudslide can have many shelves.Mudslides of 2010
The following is a list of major landslides or mudslides causing the death of at least 30 people in the world in 2010:Jan. 1: Heavy rain triggered two mudslides on the Ilha Grande resort near the Brazilian city of Rio de Janeiro
Rio de Janeiro
Rio de Janeiro , commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th...
. A luxury hotel was swept away, killing at least 30 people.
March 1: Ninety-four bodies were found and 320 people were reported missing after a mudslide spawned by torrential rains in the district of Bududa
Bududa
Bududa is a town in Eastern Uganda. It is the main municipal, administrative and commercial center of Bududa District. The district was named after the town.-Location:...
in eastern Uganda engulfed three villages.
April 5: Floods and mudslides in the Brazilian state of Rio de Janeiro
Rio de Janeiro
Rio de Janeiro , commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th...
killed at least 212 and injured 161. More than 100 were reported missing.
June 15: Powerful landslides triggered by heavy rains killed at least 48 people and left dozens of others missing in southeastern Bangladesh
Bangladesh
Bangladesh , officially the People's Republic of Bangladesh is a sovereign state located in South Asia. It is bordered by India on all sides except for a small border with Burma to the far southeast and by the Bay of Bengal to the south...
.
June 17: Torrential rains triggered mudslides on the border area between western Myanmar
Myanmar
Burma , officially the Republic of the Union of Myanmar , is a country in Southeast Asia. Burma is bordered by China on the northeast, Laos on the east, Thailand on the southeast, Bangladesh on the west, India on the northwest, the Bay of Bengal to the southwest, and the Andaman Sea on the south....
and Bangladesh
Bangladesh
Bangladesh , officially the People's Republic of Bangladesh is a sovereign state located in South Asia. It is bordered by India on all sides except for a small border with Burma to the far southeast and by the Bay of Bengal to the south...
, killing at least 46 people.
June 21: Floods and landslides in northeastern Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
killed at least 44 people, leaving more than 1,000 missing.
Aug. 6: Abrupt torrential rains triggered mudslides in India-controlled Kashmir's Leh region, killing at least 166 people. Another 400 were reported missing.
Aug. 7: At least 63 people were killed in landslides and mudslides in northern Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
.
Aug. 8: Massive rain-triggered mudslides hit Zhouqu county of Gansu province in northwestern China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, killing at least 1,467 people and left 298 others missing until Aug. 30.
Sept. 2-5: Three days of torrential rains set off scores of landslides across Guatemala
Guatemala
Guatemala is a country in Central America bordered by Mexico to the north and west, the Pacific Ocean to the southwest, Belize to the northeast, the Caribbean to the east, and Honduras and El Salvador to the southeast...
, killing at least 45 civilians and rescuers, affecting some 50,000 people and causing an economic loss of 375 million to 500 million U.S.dollars.
Sept. 28-29: Torrential rains triggered floods and mudslides in Oaxaca state and Chiapas state in southern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, causing at least 33 deaths.
Largest recorded mudslide
The world's largest historic landslide (in terms of volume) occurred during the 1980 eruption of Mount St. HelensMount St. Helens
Mount St. Helens is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It is south of Seattle, Washington and northeast of Portland, Oregon. Mount St. Helens takes its English name from the British diplomat Lord St Helens, a...
, a volcano in the Cascade Mountain Range in the State of Washington, USA. The volume of material was 2.8 km³. Directly in the path of the huge mudslide was Spirit Lake. Normally a chilly 5°C, the mudslide instantly raised the temperature to near 38°C. Today the bottom of Spirit Lake is 100 feet above the original surface. The lake now has two and a half times more surface area than it did before the eruption.
However, the world's largest prehistoric landslide, discovered to date, took place in south-western Iran
Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
, and is named the Saidmarreh Landslide. The landslide was located on the Kabir Kuh anticline in Southwest Iran
Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
at 33 degrees N, 47.65 degrees E. The landslide had a volume of about 20 cubic kilometers, a depth of 300 m, a travel distance of 14 km and a width of 5 km. This means that about 50 billion tons of rock moved in this single event alone.
Areas at Risk
The area most generally recognised as being at risk of a dangerous mudslide are:- Areas where wildfires or human modification of the land have destroyed vegetation
- Areas where landslides have occurred before
- Steep slopes and areas at the bottom of slopes or canyons
- Slopes that have been altered for construction of buildings and roads
- Channels along a stream or river
- Areas where surface runoff is directed
Protection against Mudslides
Before intense rainfall or storms, check to see if your area has had mudslides in the past, and educate yourself regarding local area evacuation or emergency plans. Families should also consider making their own emergency plan, and may wish to consider permanently leaving an area where mudslides are frequent.During intense rainfall or storms, listen to weather warnings on the radio, look for tilted trees or posts, and listen for rumbling sounds which might indicate that a landslide or mudslide is approaching. If you see a small trickle of mud in a wash, creek or stream, move away from the area as quickly as possible; it may be a warning sign that a larger flow is imminent. Finally, if you do see a mudslide approaching, you should get to high ground out of its path as quickly as possible. If you see rocks or other debris approaching your position, find shelter and take cover, if possible under a piece of heavy furniture such as a desk or table.
After a mudslide has occurred, check for injured or trapped people, but try to avoid entering the mudslide's path. Listen for emergency instructions on the radio or TV. If you see that utility lines or cables in the area are broken, report them to the proper authorities as soon as possible.