There are 118 valley debris flows and 33 slope debris flows in Batang County,Sichuan Province,China.All the vegetation coverage of these hazards has been verified through remote sensing and field investigation.It was found that the vegetation had an effect on the slope debris flow,while there was no correlation between the vegetation and valley debris flows.This difference exists because of the material source in different types of debris flows.The main material source of the slope debris flow results from surface erosion.Vegetation roots can restrain the erosion effect.But,the main sources of valley debris flow are collapses and landslides in the valley.In this case,vegetation does not work because of the deep slip surface in most collapses and landslides.So we suggest that bioengineering should be use for mitigating the slope debris flow.For valley debris flows,the vegetation is neither an active standard nor an approach to mitigation.

Vegetation can effectively control slope debris flows, but not valley debris flows, due to different material sources.

Effect of Different Types of Vegetation on the Debris Flow Control

Key Takeaway: Vegetation can effectively control slope debris flows, but not valley debris flows, due to different material sources.