Exploring the initiating mechanism, monitoring equipment and warning indicators of gully-type debris flow for disaster reduction: a review

Debris flow is a type of natural disaster characterized by sudden outbreaks, rapid movement, short duration, and extreme destructive power, posing a serious threat to human lives and property. Among debris flow events, gully-type debris flows constitute a significant proportion. Therefore, comprehending the mechanisms that trigger gully-type debris flows is of great practical importance. Based on the unique characteristics of these debris flows in various regions, choosing suitable monitoring equipment and setting up a dependable early warning system for gully-type debris flows is essential. This study overviews the initiating mechanisms, monitoring equipment, and warning indicators of gully-type debris flows. The primary source of gully-type debris flow formation is loose material sources formed by landslides and rockfalls in the middle reaches of the valley. These rich loose material sources serve as the basis for initiating debris flows, where water acts as the triggering factor. The determination of key indicators and identification criteria forms the basis for debris flow early warning. Early warning during the initiation stage of gully-type debris flows is the most time-sensitive, and the prompt recognition of debris flow initiation is the ultimate goal of early warning. Monitoring vibration characteristics offers advantages in predicting gully-type debris flows, enabling the selection of natural frequency and related parameters as key warning indicators. In the future, establishing a multi-source data monitoring and early warning system for the source area of gully-type debris flows is one of the effective ways to reduce the chain disaster of debris flow and ensure the safety of people in mountainous areas.