Through field investigation

remote sensing interpretation and geological activity history at Aizi Gully we analyze the impact factors of"6·28"debris flow

then discuss the cause of "6·28"debris flow at Aizi Gully:due to the effect of frequent earthquake

human activity and extreme drought

due to the effect of intense rainfall

debris flow initiated on slope and branches firstly

heavy rainfall makes the block body burst into torrents in short time

as a result of the strong scour capability of torrents

the materials in the gully bed is initiated

during the process of movement bank to be collapsed

material and many boulders are mixed with it along the midstream and downstream

finally the severe debris flow is formed.Through morphological investigation to calculate the discharge

total volume and one time solid material volume of 6·28debris flow at Aizi Gully are obtained.The corresponding values are 925.91m3/s

57.4×104 m3 and 27×104 m3 respectively.Study on the loose solid material condition

topographic condition and climatic characteristics we obtain the preliminary result:in recent years the debris flow frequency and scale at Aizi Gully will lessen

but if extreme drought

earthquake and intense rainfall occurr simultaneously

a large scale debris flow will be triggered.