Debris flow

debris flowsdebris basinbasinsChanneled debris flowsdebrisdebris collapsedebris-coveredrock debris
Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors.wikipedia
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Armero tragedy

Armero19851985 eruption
Notable debris-flow disasters of the twentieth century involved more than 20,000 fatalities in Armero, Colombia in 1985 and tens of thousands in Vargas State, Venezuela in 1999.
As pyroclastic flows erupted from the volcano's crater, they melted the mountain's glaciers, sending four enormous lahars (volcanically induced mudflows, landslides, and debris flows) down its slopes at 50 km/h.

Vargas tragedy

1999 Vargas mudslideOrion (dog)Vargas mudslides
Notable debris-flow disasters of the twentieth century involved more than 20,000 fatalities in Armero, Colombia in 1985 and tens of thousands in Vargas State, Venezuela in 1999.
The Vargas tragedy was a natural disaster that occurred in Vargas State, Venezuela on 14–16 December 1999, when torrential rains caused flash floods and debris flows that killed tens of thousands of people, destroyed thousands of homes, and led to the complete collapse of the state's infrastructure.

Mudflow

mudslidemudslidesmud flow
Media reports often use the term mudflow to describe debris flows, but true mudflows are composed mostly of grains smaller than sand.
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.

Landslide

landslideslandslipdebris avalanche
They generally have bulk densities comparable to those of rock avalanches and other types of landslides (roughly 2000 kilograms per cubic meter), but owing to widespread sediment liquefaction caused by high pore-fluid pressures, they can flow almost as fluidly as water.
The term landslide or less frequently, landslip, refers to several forms of mass wasting that include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows.

Landslide classification

causes of landslideslandslidesblock slide
They generally have bulk densities comparable to those of rock avalanches and other types of landslides (roughly 2000 kilograms per cubic meter), but owing to widespread sediment liquefaction caused by high pore-fluid pressures, they can flow almost as fluidly as water.
Description: "Debris flow is a very rapid to extremely rapid flow of saturated non-plastic debris in a steep channel" (Hungr et al.,2001)

Hyperconcentrated flow

hyperconcentrateddensity
Sediment-rich water floods with solid concentrations ranging from about 10 to 40% behave somewhat differently from debris flows and are known as hyperconcentrated floods.
A hyperconcentrated flow is a two-phase flowing mixture of water and sediment in a channel which has properties intermediate between fluvial flow and debris flow.

Lahar

laharsmudflowsvolcanic mudflows
A lahar is a debris flow related in some way to volcanic activity, either directly as a result of an eruption, or indirectly by the collapse of loose material on the flanks of a volcano.
A lahar (, from ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water.

Turbidity current

turbiditicturbidity currentsturbidity flow
However, underwater mudflows are prevalent on submarine continental margins, where they may spawn turbidity currents.

Sorting (sediment)

sortingwell-sortedpoorly sorted
This poor sorting of sediment grains distinguishes debris-flow deposits from most water-laid sediments.
The degree of sorting may also indicate the energy, rate, and/or duration of deposition, as well as the transport process (river, debris flow, wind, glacier, etc.) responsible for laying down the sediment.

The Control of Nature

In 1989, as part of his large-scale piece David Gordon's United States, and later, in 1999, as part of Autobiography of a Liar, choreographer David Gordon brought together the music of Harry Partch and the words of John McPhee from The Control of Nature, read by Norma Fire, in a dance titled "Debris Flow", a "harrowing taped narrative of a family's ordeal in a massive L.A. mudslide..."
The residents of the San Gabriel Mountains have had little success in preventing debris flows from destroying their houses.

Illhorn

Illgraben is best known for its literal breaking apart as the ancient mud that forms the mountain breaks apart, causing the resulting debris flows and mud slides.

Soil

soilsdirtsoil moisture
Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors.

Rock (geology)

stonerockrocks
Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors.

Stream

creekstreamscreeks
Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors.

Bulk density

bulk densitiesbulkbulk weight (density)
They generally have bulk densities comparable to those of rock avalanches and other types of landslides (roughly 2000 kilograms per cubic meter), but owing to widespread sediment liquefaction caused by high pore-fluid pressures, they can flow almost as fluidly as water.

Liquefaction

liquefyliquefiedliquification
They generally have bulk densities comparable to those of rock avalanches and other types of landslides (roughly 2000 kilograms per cubic meter), but owing to widespread sediment liquefaction caused by high pore-fluid pressures, they can flow almost as fluidly as water.

Pore water pressure

pore pressurepore fluid pressurepore pressures
They generally have bulk densities comparable to those of rock avalanches and other types of landslides (roughly 2000 kilograms per cubic meter), but owing to widespread sediment liquefaction caused by high pore-fluid pressures, they can flow almost as fluidly as water.

Colombia

COLRepublic of ColombiaColombian
Notable debris-flow disasters of the twentieth century involved more than 20,000 fatalities in Armero, Colombia in 1985 and tens of thousands in Vargas State, Venezuela in 1999.

Venezuela

VenezuelanBolivarian Republic of VenezuelaVEN
Notable debris-flow disasters of the twentieth century involved more than 20,000 fatalities in Armero, Colombia in 1985 and tens of thousands in Vargas State, Venezuela in 1999.

Sediment

sedimentslake sedimentdregs
Debris flows have volumetric sediment concentrations exceeding about 40 to 50%, and the remainder of a flow's volume consists of water.

Clay

claysblue clayammonia-rich clays
By definition, “debris” includes sediment grains with diverse shapes and sizes, commonly ranging from microscopic clay particles to great boulders.

Boulder

bouldersblocksBoulder, Colorado
By definition, “debris” includes sediment grains with diverse shapes and sizes, commonly ranging from microscopic clay particles to great boulders.

Sand

sand grainsandybeach sand
Media reports often use the term mudflow to describe debris flows, but true mudflows are composed mostly of grains smaller than sand.

Continental margin

passive continental margincontinental slopeactive continental margin
However, underwater mudflows are prevalent on submarine continental margins, where they may spawn turbidity currents.

Large woody debris

woody debris
Debris flows in forested regions can contain large quantities of woody debris such as logs and tree stumps.