In the early morning of August 18, 2022, a flash flood occurred in Datong Hui and Tu Autonomous County, Xining City, Qinghai Province, resulting in 26 deaths and 5 missing. This flash flood is a typical event of multiple casualties caused by a creek disaster. The superimposed effect of rainfall directly led to this flash flood. The early continuous rainfall caused soil moisture content to reach or approach saturation. On the night of August 17, 2022, local short-time heavy rainfall smashing historical records, which could not infiltrate into the soil or be retained by vegetation, resulted in a flash flood. As revealed by the comprehensive analysis of remote sensing data, digital elevation model, field data, and media data, the flash flood area exhibited a large catchment area, a narrow river valley, a high relative height difference, a shallow river channel, and many obstacles. Consequently, the flash flood manifested high potential energy, a long movement distance, and locally severe backwater overflow, destroying some houses, farmland, and roads on both sides of the river channel. Against the backdrop of global changes, low-risk areas of flash floods, including the arid region of northwest China and the Qinghai-Tibet Plateau, display significantly increased precipitation and frequent local short-time heavy rainfall. Hence, creeks in these low-risk areas are exposed to increasing risks of flash floods and even catastrophic ones. Additionally, heavy rainfall might induce the recurrence of flash floods in disaster areas.