Abstract:August 13

2010

heavy rainfall happened in LongChi

Dujiangyan.The recorded rainfall was 75mm in one hour from 16:00 to 17:00 o’clock

The heavy rain caused powerful flood in the catchments

which triggered material sources and destroyed prevention dams in the Bayi gully. Then the giant debris flow were formed. Based on field investigation and analysis: formation conditions of the debris flow，like topography

water source and sediment source

were firstly analyzed; Then

elaborated characteristics and formation of debris flow；Third

dynamic parameters were calculated: density is 1.88g•cm－３，discharge is 1 082m３•ｓ－１

yield stress of debris flows is more than 6700 Pa

The total volume of sediment in debris flows were estimated at 116×104ｍ3

the large boulder involving in debris flows in depositional fans have powerful impact force.Finally

the development trend of the debris flow was predicted: Because there are a lot of collapse and landslide in the drainage basins

so it have maximum possibility of happening large-scale debris flow in continuous heavy rainfall.