RESEARCH ON THE 61|DEBRIS FLOW HAZARDS IN MEIGU COUNTY OF LIANGSHAN STATE,SICHUAN

Studies on the 6.1 debris flows in Meigu county of Liangshan state,Sichuan show that the return periods of the debris flows are approximately 20 years and are small/moderate magenitude debris flows.The rainstorm and hail with short duration and high density in the upper reaches of the drainage basins are the triggering factors for the debris flows.The degenerate ecological environment in the drainage basin,unstable slopes in the low-middle reaches and a lot of unconsolidated materials in the channels of the gullies,provide enough materials for the debris flows.The debris flows are typically of the grain curve characteristics with multiple peaks.The deposits of the debris flows have a high content of clay.The large boulders,the boulder piling up boulder,mud crack,lateral accumulation mound and surge deposits demonstrate the debris flows are viscous.Hazardousness assessment indicates,the Caimoluo gully is a high hazardous debris flow gully and has the hazard degree of 0.67;the Naituo gully is a moderate hazardous debris flow gully and has the hazard degree of 0.58.Risk assessment implies the two gullies have high debris flow risk,respectively with the risk degree of 0.52 and 0.45.The debris flows occurred in the high risky area resulted in huge losses of property and life.