In the early morning of August 3, 2024, a super-large mountain flood and debris flow disaster broke out in Ridi gully, Guza Town, Kangding, Sichuan Province, causing great losses to local residents, Yakang Expressway and infrastructure. Taking the Ridi gully debris flow as an example, the disaster characteristics and development process of the event were revealed through field investigation, remote sensing interpretation, calculations and analyses of snowmelt water output, HI(height integral), and other parameters. The debris flow was subsequently simulated and verified using the Massflow software. The results show that short-term heavy rainfall is the direct cause of the Ridi gully debris flow, while the long-term rainfall in the early stage, the rapidly warming snowmelt water, frequent earthquakes and mature erosional landform evolution indirectly contribute to the formation of debris flow. At the same time, earthquakes and erosion landforms also increase the possibility of debris flow blockage and the scale of debris flow. Combined with numerical simulation calculation methods, through the comparison of measured and simulated accumulation areas, the verification results show that the accumulation area of the model considering the channel blockage coefficient is closer to the measured value. This study analyzes the dynamic characteristics of debris flows more intuitively, in order to provide a theoretical basis for disaster prevention and mitigation work for similar debris flows.