Debris flow/earth flow
A debris flow is a mixture of water and solids content of 30–60% (boulders, rock material) which usually moves downhill in mountain torrents with a fast flow rate. It is more commonly known as a mudslide or boulder avalanche (mud flow).
Earth flows, commonly known as landslides or mudslides, often occur on slopes that are steep and saturated with water. It is when the surface layers of a slope spontaneously slide downhill.
Debris flows can be triggered, for example, by heavy rainfall or when log jams in mountain torrents collapse. They are able to transport an enormous amount of debris, easily carrying entire tree trunks and boulders several cubic metres in size. The high volume of water means that they can reach speeds of many dozens of kilometres per hour, which makes almost any kind of advance warning impossible and the likelihood of escape virtually nil. Debris flows are highly destructive, putting people inside and outside buildings at risk.
Small, superficial landslides usually only cause damage to farmland, but the spillage can also temporarily block roads. However, if the volume increases, it can also move or bury entire sections of road and houses.