The distribution of debris flow in our country is obviously controlled
by topography, geology and precipitation conditions, especially
in the terrain. Debris flow in China is concentrated in two belts.
One is the contact zone between the plateau and the basin of the
Qinghai-tibet plateau. The other is the above plateau, basin,
and the low hills in east or the transitional zone of plain.
In the above two belts, the debris flow is concentrated on the two sides of
the river gullies, which are large faults and deep fractures. This is the area
where the mudslide disasters happen with the highest density,
the most frequency and the most serious damage.
In each big tectonic belt, mudslides with a high frequency of debris flow
tend to focus on the slate, schist, gneiss, mixed granite, phyllite and
metamorphic rock series and mudstone, shale, marl, coal measures and
other weak rock series and the distributive zones of the quaternary deposits.
The distribution of debris flow is closely related to the significant
features of atmospheric precipitation and melting of snow and ice.
That is, debris flow with high frequency mainly distributed in the
climate that dry and wet season is obvious and warm and wet and areas
that have heavy local rain, and water and snow melt fast. Such as Yunnan,
Sichuan, Gansu, Tibet and so on. Sparse debris flow with low frequency
is mainly distributed in the northeast and southern regions.