摘要
Group debris flows occurred on August 14,2010 in Yingxiu area,epicenter of Wenchuan earthquake,Sichuan province,which caused enormous life and property losses.The debris flows are very active because of the abundant loose materials in earthquake-stricken areas,it is the primary work for the management and control of debris flow risk to estimate the scale and hazard under different rainfall frequencies in the future.The empirical formula between debris flow scale and rainfall frequency was obtained by collecting and studying the datum.The scales of 13 debris flows under different rainfall frequencies were calculated through the empirical formula with the basic datum of "8.14"debris flows scales and rainfall frequency in Yingxiu area along the Minjiang river.Chosen the average deposition thickness of alluvial fan(scale / alluvial fan area),occurrence frequency,drainage area,channel length,basin relative height,valley incision density and instability gully cutting proportion as hazard judgment factors,the debris flow hazards of 13 gullies were assessed under the rainfall return period of 100 years,50 years,20 years,10 years and 5 years in Yingxiu area.The results indicated that debris flow hazards of 8 gullies were high under 5 rainfall frequencies,debris flow hazards of 4 gullies were moderate to high under different rainfall frequency,the remaining one was moderate hazard under 5 rainfall frequencies.The method using average deposition thickness on alluvial fan as the variable factor of hazard assessment can better estimate the debris flow hazard in different rainfall frequency.
