Aizi gully in Ningnan country Sichuan province occurred debris flow on 28,June 2012 and caused serious casualties.Based on the field survey after the occurrence of debris flow and the interpretation of satellite im-age data with 0.5 meter resolution ratio before debris flow occurrence(February 2012)and after the event (January 2013),the difference characteristics of debris flow gully are analyzed and compared.Results show that the debris flow process in 2012 is typical hydraulic-driven type,the process can be divided into four process:① The heavy rainfall generate the slope flow in short time,and the flow damage the stability of deposit on slope by erosion and initiates slope debris flow,then the slope debris flow run into channel of Aizi gully.②The slope debris flow cuts and erodes the gully bed intensively and damages the stability of deposit,then initiates the louse soil in the bed.③After the cutting by flow in channel,the deposit in the channel bed continue damaged from upstream to downstream and provides enough loose source to debris flow movement and enlarge it′s volume.④The kinetic energy of debris flow decreased at the limitation of landform and turn into deposit,which means the finish of debris flow process. The results from the loose source supply shows that the source for debris flow initiation can be divided into two types,one is initiating source which provide necessary loose source for the first step of debris flow initiation,the other one is the maintaining source which provide the loose source to maintain the continue movement and enlarge the volume of debris flow.Based on the comparison of the mechanism of source supply in Aizi debris flow to others debris flow events,it is found that there have the obviously two source supply phases for lower return period debris flow process,which can be useful for it′s mitigation.%2012年6月28日四川省宁南县矮子沟暴发泥石流，造成重大的人员伤亡和财产损失。通过对比事件前后流域的高精度遥感影像，并结合泥石流发生后野外调查情况进行综合分析。研究结果表明：矮子沟泥石流具有典型水力类泥石流的启动机制，其形成过程可分为四个阶段：①强降雨使得地表径流快速汇集，使得坡体表层土产生破坏并启动，形成坡面泥石流并汇入主沟；②具有极强侵蚀能力的坡面泥石流开始对沟床内的固体物质产生强烈的揭底侵蚀和侧蚀，使得沟床堆积体的稳定性产生破坏并启动；③沟床堆积物在受到揭底侵蚀后，从上游依次往下，形成连续性的破坏并为泥石流的形成持续提供固体物质，以维持泥石流的运动并放大其规模；④在达到海拔800 m沟口转弯处之后，由于受到地形的限制及泥石流自身的动能衰减并产生堆积，泥石流过程结束。通过对该次泥石流的物源补给过程进一步研究认为，其物源补给可分为形成泥石流流体所需的启动型物源和维持泥石流持续运动的维持型物源两类。通过对比发现，低频泥石流在启动过程中的物源补给过程具有明显的启动型物源和维持型物源两个相对微观物源补给类型及过程，可为这类泥石流防治工程的类型选择及设计提供重要的理论依据。
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