A mudflow or mud flow is a form of mass wasting involving "very rapid to extremely rapid surging flow"[1] of debris that has become partially or fully liquified by the addition of significant amounts of water to the source material.[2]

Mudflows contain a significant proportion of clay, which makes them more fluid than debris flows; thus, they are able to travel farther and across lower slope angles. Both types are generally mixtures of various kinds of materials of different sizes, which are typically sorted by size upon deposition.[3]

Mudflows are often called mudslides, a term applied indiscriminately by the mass media to a variety of mass wasting events.[4] Mudflows often start as slides, becoming flows as water is entrained along the flow path; such events are often called flow slides.[5]

Other types of mudflows include lahars (involving fine-grained pyroclastic deposits on the flanks of volcanoes) and jökulhlaups (outbursts from under glaciers or icecaps).[6]

A statutory definition of "flood-related mudslide" appears in the United States' National Flood Insurance Act of 1968, as amended, codified at 42 USC Sections 4001 and following.

MSH80 mailboxes along cowlitz river 1980
Mailboxes caught in a mudflow following the May 1980 Saint Helens volcanic eruption.

Triggering of mudflows

The Mameyes mudflow disaster, in barrio Tibes, Ponce, Puerto Rico, was caused by heavy rainfall from Tropical Storm Isabel in 1985. The mudflow destroyed more than 100 homes and claimed an estimated 300 lives.

Heavy rainfall, snowmelt, or high levels of ground water flowing through cracked bedrock may trigger a movement of soil or sediments. Floods and debris 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 hills around Los Angeles, California, where they have destroyed many homes built on hillsides without sufficient support after fires destroy vegetation holding the land.

The point where a muddy material begins to flow depends on its grain size 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 mudflow known as The Vargas tragedy significantly altered more than 60 kilometers (37 mi) of the coastline. It was triggered by heavy rainfall and caused estimated damages of US$1.79 to US$3.5 billion, killed between 10,000 and 30,000 people, forced 85,000 people to evacuate, and led to the complete collapse of the state's infrastructure.

Mudflows and landslides

Landslide is a more general term than mudflow. It refers to the gravity-driven failure and subsequent movement downslope of any types of surface movement of soil, rock, or other debris. The term incorporates earth slides, rock falls, debris flows, and mudslides, amongst other categories of hillslope mass movements.[7] They do not have to be as fluid as a mudflow.

Mudflows can be caused by unusually heavy rains or a sudden thaw. They consist mainly of mud and water plus fragments of rock and other debris, so they often behave like floods. They can move houses off their foundations or bury a place within minutes because of incredibly strong currents.

Mudflow geography

When a mudflow occurs it is given four named areas, the 'main scarp', in bigger mudflows 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 there is a large dip (due to mountain or natural drop) in the mudflow's path. A mudflow can have many shelves.

Largest recorded mudflow

The world's largest historic landslide (in terms of volume) occurred during the 1980 eruption of Mount St. Helens, a volcano in the Cascade Mountain Range in the State of Washington, USA. The volume of material displaced was 2.8 km3 (0.67 cu mi). Directly in the path of the huge mudflow was Spirit Lake. Normally a chilly 5 °C (41 °F), the lahar instantly raised the temperature to near 38 °C (100 °F). Today the bottom of Spirit Lake is 100 ft (30 m) above the original surface, and it has two and a half times more surface area than it did before the eruption.

The world's largest known prehistoric terrestrial landslide took place in southwestern Iran, and is named the Saidmarreh landslide. The landslide was on the Kabir Kuh anticline at 33.0°N, 47.65°E. The landslide had a volume of about 20 km3 (4.8 cu mi), a depth of 300 m (980 ft), a travel distance of 14 km (8.7 mi), and a width of 5 km (3.1 mi). This means that about 50 billion tons of rock moved in this single event.

The largest known of all prehistoric landslides was an enormous submarine landslide that disintegrated 60,000 years ago and produced the longest flow of sand and mud yet documented on Earth. The massive submarine flow travelled 1,500 km (930 mi) – the distance from London to Rome.

By volume, the largest submarine landslide (the Agulhas slide off South Africa) occurred approximately 2.6 million years ago. The volume of the slide was 20,000 km3 (4,800 cu mi).

Areas at risk

The area most generally recognized as being at risk of a dangerous mudflow 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 streams and rivers
  • Areas where surface runoff is directed

See also


  1. ^ 3 meters/minute to 5 meters/second; Hungr, Leroueil & Picarelli 2014, Table 2, citing Cruden and Varnes, 1996.
  2. ^ Hungr, Leroueil & Picarelli 2014, p. 185; Hungr, Leroueil & Picarelli 2013, p. 28
  3. ^ Hungr, Leroueil & Picarelli 2014, pp. 170, 185
  4. ^ Hungr, Leroueil & Picarelli 2013, p. 4
  5. ^ Hunger, Leroueil & Picarelli 2013, §6.1 Flow slides; Hungr, Leroueil & Picarelli 2014, p. 167
  6. ^ Hungr, Leroueil & Picarelli 2014, p. 185
  7. ^ "What is a Landslide? - Geoscience Australia". 2014-05-15. Retrieved 2015-12-16.


External links

2002 Northern Chile floods and mudflow

The 2002 Northern Chile floods and mudflow were a series of flash floods and mudflows that affected north-central Chile in early June 2002. The floods and mudflows were the result of heavy rains in the area. Overall 17 human casualties can be attributed to the rainfalls. Among the casualties, there were twelve direct deaths, four indirect deaths and one disappearance. The Locality of Los Molles was particularly badly affected.According to National Office of Emergency of the Interior Ministry (ONEMI) 71 and 347 houses were destroyed in Coquimbo and Valparaíso regions respectively.

2002 in Chile

The following lists events that happened during 2002 in Chile.

2010 Gansu mudslide

The 2010 Gansu mudslide was a deadly mudslide in Zhouqu County, Gannan Tibetan Autonomous Prefecture, China that occurred at 12 midnight on 8 August 2010. It was caused by heavy rainfall and flooding in Gansu Province. It was the most deadly individual disaster of the 2010 China floods. The mudslides killed more than 1,471 people as of 21 August 2010, while 1,243 others have been rescued and 294 remain missing. The missing were presumed dead as officials ordered locals to stop searching for survivors or bodies to prevent the spread of disease. Over 1,700 people evacuated have been living in schools.

2015 Northern Chile floods and mudflow

The 2015 Northern Chile floods were a series of mudflows that affected much of northern Chile, product of flash floods from different rivers due to unseasonal heavy rains in the area, causing severe damage in several towns of the Antofagasta, Atacama and Coquimbo regions.

Flooding in Chile and Peru resulted from an unusual cold front which moved across the Andes, bringing heavy rainfall to the region.The National Office of Emergency of the Interior Ministry (ONEMI) has reported more than 27,413 people affected, 5,585 people on shelters and more than 300 isolated due to roads destruction.

26 people died during the mudflow and 101 are officially missing, although it is expected that these numbers will increase as contact is reestablished with remote communities.

Preliminary figures show that property damage reaches more than 28,000 houses, of those 105 are completely destroyed, and at least 5,900 present severe damages.

2018 Sulawesi earthquake and tsunami

On 28 September 2018, a shallow, large earthquake struck in the neck of the Minahasa Peninsula, Indonesia, with its epicentre located in the mountainous Donggala Regency, Central Sulawesi. The magnitude 7.5 quake was located 77 km (48 mi) away from the provincial capital Palu and was felt as far away as Samarinda on East Kalimantan and also in Tawau, Malaysia. This event was preceded by a sequence of foreshocks, the largest of which was a magnitude 6.1 tremor that occurred earlier that day.Following the mainshock, a tsunami alert was issued for the nearby Makassar Strait, but was called off half an hour later. A localised tsunami struck Palu, sweeping shore-lying houses and buildings on its way. The combined effects of the earthquake and tsunami led to the deaths of an estimated 4,340 people. This makes it the deadliest earthquake to strike the country since the 2006 Yogyakarta earthquake, as well as the deadliest earthquake worldwide in 2018, surpassing the previous earthquake that struck Lombok a few months earlier, killing more than 500. The Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG) confirmed that a tsunami had been triggered, with its height reaching an estimated maximum of 4 to 7 metres (13 to 23 ft), striking the settlements of Palu, Donggala and Mamuju along its path.The earthquake caused major soil liquefaction in areas in and around Palu. In two locations this led to mudflows in which many buildings became submerged causing hundreds of deaths with many more missing. The liquefaction was considered to be the largest in the world and was deemed as rare.

Aburizal Bakrie

Aburizal Bakrie (born 15 November 1946) is an Indonesian politician, and widely recognised as successful businessmen in Indonesia. From 2004 until 2005 Bakrie served as Indonesia's Coordinating Minister for Economy. From 2005 until 2009 he served as Coordinating Minister for People's Welfare. Since 2009, Bakrie served as the Chairman of the Golkar Party up to late 2014, and resumed chairmanship in May 2015.

Corcovado Volcano

Corcovado Volcano (Spanish pronunciation: [koɾkoˈβaðo]) is a stratovolcano located about 25 kilometres (16 mi) south of the mouth of Yelcho River, in the Palena Province, Los Lagos Region, Chile. The glacially eroded volcano is flanked by Holocene cinder cones. The volcano's base has likely prehistoric lava flows that are densely vegetated. The most distinctive feature of this volcano is its stepped top, similar to that of Puntiagudo Volcano. At its foot lies a series of beautiful lakes. Corcovado dominates the landscape of Gulf of Corcovado area and is visible from the Chiloé Island, weather allowing.

The volcano and the adjacent area form part of Corcovado National Park. The town of Chaitén was formerly the main gateway to this protected area, but much of the town was destroyed by an eruption of Chaitén Volcano and mudflow in 2008.


An earthflow (earth flow) is a downslope viscous flow of fine-grained materials that have been saturated with water and moves under the pull of gravity. It is an intermediate type of mass wasting that is between downhill creep and mudflow. The types of materials that are susceptible to earthflows are clay, fine sand and silt, and fine-grained pyroclastic material.When the ground materials become saturated with enough water, they will start flowing (soil liquefaction). Its speed can range from being barely noticeable to rapid movement. The velocity of the flow is dictated by water content: the higher the water content is, the higher the velocity will be. Because of the dependency on water content for the velocity of the flow, it can take minutes or years for the materials to move down the slope.

Kautz Glacier

The Kautz Glacier is a narrow glacier on the southern flank of Mount Rainier in Washington. Named for August Kautz, who is sometimes credited for the first ascent of Mount Rainier, covers 1.8 square miles (4.7 km2) and contains 7.8 billion ft3 (221 million m3) of ice. Upper Kautz Glacier extends south from the summit ice cap to Kautz Ice Cliff at about 11,700 feet (3,600 m). Immediately west of the main ice cliff, the glacier continues down Kautz Chute which terminates in another ice cliff just above the lower Kautz Glacier at 10,800 feet (3,300 m). Usually reached by a short descent from Camp Hazard at 11,300 feet (3,400 m) on Wapowety Cleaver, climbers following the Kautz Glacier climbing route ascend this chute to the upper glacier.Starting from the Kautz Glacier Headwall at about 12,500 feet (3,800 m), the lower glacier flows generally south-southwest between the Kautz and the Wapowety Cleaver. Just before it meets the Success Glacier, the Kautz makes a right turn and heads west for a short distance. After the two glaciers meet, the resultant glacier reaches down to about 6,000 ft (1,800 m) before terminating. Meltwater from the glacier drains into Kautz Creek Falls and into Kautz Creek, a tributary of the Nisqually River.


A lahar ( , from Javanese: ꦮ꧀ꦭꦲꦂ, romanized: wlahar) is a violent 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.Lahars are extremely destructive: they can flow tens of metres per second (22 mph or more), they have been known to be up to 140 metres (460 ft) deep, and large flows tend to destroy any structures in their path. Notable lahars include those at Mount Pinatubo and Nevado del Ruiz, the latter of which covered entire towns and killed thousands of people.

Lake Kapowsin

Lake Kapowsin is a lake in Pierce County, Washington, about halfway between Tacoma on Puget Sound, and Mount Rainier in the Cascade Mountains. The lake is 2.5 miles (4.0 km) long and 0.15–0.5 miles (0.24–0.80 km) wide, lying in a channel formed by meltwater from the Puget lobe of the Vashon glacier during the Pleistocene glaciation. A small unnamed island lies in the northern half of the lake. As indicated by a drowned forest in the lake and other evidence, the Puyallup River was inundated about 550 years ago by a lahar from Mount Rainier called the Electron Mudflow. The mudflow partially filled the channel (leading to its shallow, smooth bottom today) and blocked Ohop Creek's outlet, forming present-day Lake Kapowsin.The Tacoma Rail shortline runs along the west side of the lake, as does Orville Road connecting Eatonville to the south with the town of Kapowsin.

The lake contains a number of fish species and is stocked with rainbow trout, rated "excellent" for fishing by Washington Department of Fish and Wildlife, as is the yellow perch.

Medeu Dam

The Medeu Mudflow Control Dam (Kazakh: Медеу бөгеті, Medeý bógeti) is a dam across the Medeu Valley south-east of Almaty, Kazakhstan, designed to protect the city from devastating debris flows (or mudflows).

Mount Rainier

Mount Rainier (pronounced: ), also known as Tahoma or Tacoma, is a large active stratovolcano in Cascadia located 59 miles (95 km) south-southeast of Seattle, in Mount Rainier National Park. With a summit elevation of 14,411 ft (4,392 m), it is the highest mountain in the U.S. state of Washington, and of the Cascade Range of the Pacific Northwest, the most topographically prominent mountain in the contiguous United States, and the tallest in the Cascade Volcanic Arc.

Mt. Rainier is considered one of the most dangerous volcanoes in the world, and it is on the Decade Volcano list. Because of its large amount of glacial ice, Mt. Rainier could produce massive lahars that could threaten the entire Puyallup River valley. "About 80,000 people and their homes are at risk in Mount Rainier’s lahar-hazard zones."

Osceola Mudflow

The Osceola Mudflow, also known as the Osceola Lahar, was a lahar in the U.S. state of Washington that descended from the summit and northeast slope of Mount Rainier during a period of eruptions about 5,600 years ago. It traveled down the west and main forks of the White River, passed the location of present day Enumclaw then reached Puget Sound near present day Auburn. The Osceola collapse formed a 1.8 km (1.1 mi) wide horseshoe-shaped crater, open to the northeast, almost the same size as the crater produced by the 1980 eruption of Mount St. Helens. Most of the Osceola crater has been filled in by subsequent lava eruptions, most recently about 2,200 years ago.With a volume of 2 to 3 km3 (0.48 to 0.72 cu mi) and an areal extent of about 550 km2 (210 sq mi), the Osceola Mudflow buried a large portion of the Puget Sound lowland with hydrothermally altered volcanic material. Many communities in King and Pierce counties, notably Kent, Enumclaw, Orting, Buckley, Sumner, Puyallup and Auburn, are wholly or partly located on top of Osceola Mudflow deposits.The Osceola Mudflow was Mount Rainier's signature event during the Holocene epoch. It was named after the unincorporated community of Osceola.

Porong River

Porong River is a river flowing through Sidoarjo, East Java, Indonesia, about 700 km east of the capital Jakarta. It is one of the main branches of the Brantas River that discharges into Bali Sea, close to the Madura Strait, and is the main outlet for the Lusi mudflow.

Sidoarjo mud flow

The Sidoarjo mud flow or Lapindo mud (informally abbreviated as Lusi, a contraction of Lumpur Sidoarjo wherein lumpur is the Indonesian word for mud) is the result of an erupting mud volcano in the subdistrict of Porong, Sidoarjo in East Java, Indonesia that has been in eruption since May 2006. It is the biggest mud volcano in the world; responsibility for it was credited to the blowout of a natural gas well drilled by PT Lapindo Brantas, although some scientists and company officials contend it was caused by a distant earthquake.

At its peak Lusi spewed up to 180,000 m³ of mud per day. By mid August 2011, mud was being discharged at a rate of 10,000 m³ per day, with 15 bubbles around its gushing point. This was a significant decline from the previous year, when mud was being discharged at a rate of 100,000 cubic metres per day with 320 bubbles around its gushing point. It is expected that the flow will continue for the next 25 to 30 years. Although the Sidoarjo mud flow has been contained by levees since November 2008, resultant floodings regularly disrupt local highways and villages, and further breakouts of mud are still possible.

Sidoarjo railway station

Sidoarjo Station (SDA) is an Indonesian station located in Lemahputro, Sidoarjo, Sidoarjo, East Java, Indonesia. The station passes the railway to the east (Jember-Banyuwangi) and the path to Malang-Blitar. The station located at the height of + 4 meters is included in the Operation Area VIII Surabaya.

The station initially had seven track with track 1 as a straight track, but track 5 has now been evicted for new platforms and tracks 6 and 7 have now been evicted in 1992 for the purpose of shop development. Formerly this station contained locomotive depot and warehouse, but was demolished in 1992 due to the construction of shop.

From track 4, the dead track that leads to Tarik Station is reactivated as part of the relocation of the eastern railway line following the hot mudflow in Porong.

As a first-class train station, almost all trains stop at this station. Only freight trains (tank and cement) are passing directly / do not stop.

Surabaya–Gempol Toll Road

Surabaya–Gempol Toll Road is a toll road in East Java, Indonesia. This 37-kilometre (23 mi) highway connects Surabaya City in the north with Porong in the south. This toll road passes Surabaya and Sidoarjo. It is part of the Trans-Java Expressway. The original length of this toll road from Surabaya to Gempol was 43 kilometres (27 mi) long, but the 6-kilometre (3.7 mi) part of this toll road is closed due to the overflow of Lapindo Mudflow that has inundated the Porong–Gempol section of the Surabaya–Gempol toll road since 2006.The toll road has been operating since 1986, and became the main access of Surabaya–Malang and Surabaya–Pasuruan routes which is one of the main industrial areas in East Java.

Since August 2006, this toll road has been disrupted due to the mud flood event that inundated this toll road at a point 36 kilometres (22 mi) from Surabaya, specifically in Siring Village, Porong Sub-district, Sidoarjo Regency. The Porong–Gempol Toll Road is basically a relocation of Porong–Gempol segment of the Surabaya–Gempol Toll Road that was drowned by mud flow; it was inaugurated on 20 December 2018.

Valley of Geysers

The Valley of Geysers (Russian: Долина гейзеров) is a geyser field on Kamchatka Peninsula, Russia, and has the second largest concentration of geysers in the world. This six-kilometre-long (3.7 mi) basin with approximately ninety geysers and many hot springs is situated on the Kamchatka Peninsula in the Russian Far East, predominantly on the left bank of the ever-deepening Geysernaya River, into which geothermal waters flow from a relatively young stratovolcano, Kikhpinych. Temperatures have been found to be 250 °C (482 °F), 500 m (1,600 ft) below the caldera ground. It is part of the Kronotsky Nature Reserve, which, in turn, is incorporated into the World Heritage Site "Volcanoes of Kamchatka". The valley is difficult to reach, with helicopters providing the only feasible means of transport.



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