Bioengineering Mitigation of Debris Flow

Abstract

Debris flow events caused substantial damage to life, property and ecosystems in mountainous regions, demanding effective mitigation strategies. This doctoral thesis will present an examination of using vegetation barriers as a bioengineering method to reduce the mobility and the destructive potential of debris flow. The primary research aim is to investigate the effectiveness of the vegetation barriers to reduce the mobility of debris flow.

This study adopts two laboratory investigations to achieve this aim. A compaction testing analysis was one of the investigations, used to determine the ideal compaction level for the soil to plant the willow branches to encourage root growth and provide maximum pull-out resistance within 2 months of growing. The findings reveal that the best compaction level is the lowest compaction level (84 kJ/m3) adopted in this study. This is the opposite of the usual engineer instinct when it comes to slope stability.

The other investigation is a specially designed flume that allowed vegetation to be used as barriers within the flume. This flume was designed to allow the introduction of potted plants in the flume. The results showed a significant reduction in debris flow mobility and destructive energy when double-row barriers and thicker willow branches were used. These barriers effectively impede the flow’s velocity, trap sediment and reduce the potential damage experienced at the flume’s base. The distance between the two rows of vegetation barrier is also crucial as the gap distances trap the sediments and release them slowly as the debris flow passes through.

This thesis provides an evaluation of the effectiveness of vegetation barriers in mitigating debris flow mobility and the suitable compaction levels for the soil when planting willows. It emphasises the capacity of these barriers to harmonize engineering principles with ecological consideration, offering a promising pathway toward resilient and sustainable hazard management in sloping grounds.

Date of Award	2025
Original language	English
Awarding Institution	University of Dundee
Sponsors	Engineering and Physical Sciences Research Council
Supervisor	Andrew Brennan (Supervisor)