Investigation of the relationship between gully-type debris flows and shallow landslides.

Continuous heavy rainfall occurred in Shunchang County, Fujian Province, China, from June 14 to 18, 2010, causing many landslide hazards. Among Shunchang County districts, Baozhuang Village is one of the hardest-hit areas and suffered severe losses. A detailed analysis of the relationship between the catchment area and the area of landslides was carried out to explore the relationship between debris flow occurring and the provenance provided by landslides. This paper presents an empirical model to analyze gully-type debris flows caused by hillslope debris flow everywhere. Forty-three catchments in the Baozhuang Village area were selected and investigated using Google Earth Pro satellite images to estimate the area of landslides in the catchment area. The thresholds for gully-type debris flow caused by shallow landslides were defined in terms of the area of the landslides (A₀) and the catchment (A). A₀–A threshold models were constructed for debris flow catchment in Baozhuang Village using the empirical data set of debris flow by shallow landslides. The validation suggests that the proposed models are suitable for analyzing the initiation mechanism of debris flow caused by shallow landslides (or hill slope debris flows) in Fujian Province. The empirical models are simple, and the data necessary for the input are easily measurable catchment and landslide scar areas in a catchment. Owing to its simplicity and low cost-benefit rate, the approach may be applied to analyzing gully-type debris flow caused by shallow landslides in other areas. [ABSTRACT FROM AUTHOR]