The activity intensity of debris flow is mainly related to
the topography, geological environment and hydrometeorological conditions.
For example, collapse, landslide, rock community area, rock breaking,
deep weathering can easily become solid material supply source of
debris flow; The large length of the gully, the large area of the catchment
area and the steepness of the longitudinal slope provide the conditions for
the flow of the debris flow. Hydrological meteorological factors directly
provide hydrodynamic conditions.
The intensity of heavy rainfall tends to be closely related
to the intensity of rainstorm.
In the early morning of June 5, 1997, in the wake of the heavy rain,
Zezugu slope in Meigu County, Sichuan province came to life. The 21 million
steres of material went directly into the ravine and then turned into
mudslide, forming a large-scale disaster. According to statistics,
there were four villages that have been affected by the disaster, that is,
Monaihuo, Nijubaha, Zhalagu and Nijuluojia. It damaged 307 houses,
destroyed 437 hectares of farmland, damaged 210,000 kg of grain,
4,084 dead livestock and 151 people died and disappeared and the direct
economic loss amounted to 15.29 million yuan. The landslide material washed into
the ravine, some of which are moving in the form of debris flow and most of
the material accumulated in the gutter bed, causing the gully bed to
raise 100 meters and forming three barrier lakes. A landslide lake
at the bottom of the river, which was partially collapsed on June 8, 1997,
formed a mudslide again, breaking out of the loose debris of more than
20 steres, making it difficult for the local residents to produce and live.
On the morning of February 17, 2006, a huge gap was opened
up in the mountains of St. Bernard, the town on Leyte Island,
Eastern Philippines, where torrential rain was raging. The
slurry flew down with rocks, forming mudslide. The hard-hit
Jean sargon village at the foot of the mountain became giant
mire within 5 to 7 km of land instantly. In addition, 300 homes
were buried, 1800 people in the village were almost all killed
and the survivors were only more than 20 people.
Columbia Ruiz volcano erupted in November 1985, flowing
down with chippings and moya, submerging the Ameiluo town
50 kilometers away from the volcano instantly. The disaster
killed 23000 people and left 150000 livestock deaths,
130000 people homeless. The economy loss was as much as
5 billion dollars.