Mountain floods are floods in the mountain creek. They have the characteristics
of sudden, concentrated water flow velocity, erosion force, water with sand or rocks,
often caused by localized flooding. Generally divided into torrential rain,
snowmelt floods, flash floods and other glaciers. Floods, debris flow and
landslide induced, often caused casualties and destroyed houses, fields, roads,
bridges, dams, ponds and may even lead to failure, causing serious harm
to the economy and life and property.
The conditions for the formation are as follows:
General topographic feature of debris flow is formed
in the mountain area, the relative elevation, slope steep valley. The surface
is covered with a thick skin of soil, the soil below the broken rock layer is
cutting deep fault and its derived fault level.
Water source conditions
Water body is not only a part of the mountain floods
debris flow, but also the excitation factor, mainly from the rain.
The factors of human activities
Over exploitation of land in the mountainous area,
or land reclamation engineering construction on the mountain, or causing damage,
changing of topography, the destruction of natural vegetation, forest deforestation,
loss of water conservation, are prone to flash floods.
Mountain torrents can be divided into following types
according to their causes:
1) mountain torrents caused by rainstorm: under the
threat of intense rainstorm, water rapidly collects from
slope surface to gully, resulting in powerful flood which
can rush out the valley.
2) mountain torrents caused by ice and snow: ice or
snow melts quickly into water which rushes into downstream
formed mountain torrents.
3) mountain torrents caused by the burst of dams:
when flood protection and water storage facilities and
natural dams break, water burst out and contribute to
Above contributing factors may work individually or
jointly to cause mountain torrents. Among them, torrents
caused by rainstorm is the most common flood in China,
which burst out the most frequently and bring about
Heavy rainfall is the main driving force for mountain torrents.
Topography, landforms, vegetation and land use also play an important
role in the formation of mountain torrents. The formation of
mountain floods is closely related to rainfall, rainfall intensity
and rainfall history. High intensity concentrated rainfall is the
main cause of mountain torrents. The occurrence of landslides and
debris flows is closely related to the rainfall intensity in the
early period and the short diachronic rainfall. There are three
main causes, that is, the water infiltration and accumulation,
which destroy the stability of the accumulation body, the mixing
of the landslide soil and water, and water bursting banks. The
study of critical conditions for mountain floods includes the
threshold and uncertainty of surface runoff, critical rainfall
or rainfall intensity applied widely in the United States. The
research methods include statistical analysis of historical data,
hydrological history data and unit hydrologic process based on
GIS technology and remote sensing technology.