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The conditions for the formation of mountain flood

2018-10-09  |   Editor : houguangbing  

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:

Geological features

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 mountain torrents.

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 serious damage. 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.

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