Activity patterns and controlling factors of debris flows in the Upper Salween Alpine Valley

Abstract

The frequency of debris flows in mountainous areas has increased in recent years, threatening sustainable development of mountainous communities. The Upper Salween Alpine Valley (USAV) experiences the most serious debris flow disasters in China. However, activity patterns and formation mechanisms of debris flow in this area are still unclear. We analyzed debris flow activity patterns and identified their key controlling factors in the USAV based on 66-year historical data, field records, remote sensing images, and geology, gravity, and precipitation characteristics. The results showed that (1) 200 contemporary debris flow gullies were distributed with a linear density of 0.64 gully/km. Twenty-four large-scale debris flow disasters occurred in the past 66 years; (2) the activity patterns of debris flow in the USAV were characterized by double rain season, nocturnal, high concealment, low frequency, and strong destructive force; (3) the USAV was a debris-flow-prone area with strong precipitation, strong gravity, and moderate geology driving forces. It belongs to loose material-controlled debris flow region. Our findings could contribute to the understanding of formation mechanisms of debris flows, and further improve prevention and mitigation of debris flow disasters in the USAV.