Spatiotemporal patterns, controlling factors and evolutionary trends of debris flows in the Yunnan section of the Nujiang River mainstream

This paper is the result of geological hazard survey engineering.

Objective The Yunnan section of Nujiang River mainstream (YNR) experiences the most serious debris flow disasters in Yunnan Province. Historical events have caused serious casualties and property losses, highlighting the need to clarify their spatiotemporal patterns, controlling factors, and future evolution.

Methods Based on data collection, remote sensing interpretation, field investigations, and community interviews, a more detailed database of debris flow events was established, updating the historical records from 86 to 134 events. Statistical analysis and the Geodetector method were applied to assess the spatiotemporal differentiation and dominant factors.

Results (1) Debris flows are stronger in the north and weaker in the south, with Shangjiang Town, Lushui City as the dividing line. Temporally, debris flows show an overall increasing trend on the annual scale and significant differentiation on the monthly scale. (2) Climatic conditions, fault structures, and topography/geomorphology dominate the spatial pattern, while rainfall and earthquakes control temporal variations. (3) Since 2000, debris flows have exhibited an activity cycle of about three years and a rising trend of concentrated outbreaks induced by extreme rainfall and strong earthquakes.

Conclusions Historical debris flow records in the Yunnan Nujiang were updated from 86 to 134 events, which provide basic and essential data for the research on the Spatiotemporal patterns, controlling factors, and evolutionary trends of debris flows. These findings improve understanding of debris flow activity in the Yunnan section of the Nujiang River and provide scientific support for disaster prevention in towns, settlements, and critical transportation corridors.