Impact of vegetation roots on erosion protection of sandbars in laboratory experiments

• Published in: Catena (Giessen) 2025-02, Vol.249, Article 108631
• Main Authors: Li, Jin-Fu, Chiu, Yen-Yu, Chen, Su-Chin
• Format: Article
• Language: English
• Subjects: Erosion protection; Root system; Soil cohesion of roots; Vegetated sandbar
• ISSN: 0341-8162
• DOI: 10.1016/j.catena.2024.108631

•Fibrous roots are more effective in improving soil cohesion than taproots.•Taproots develop erosion-inhibiting structures that prevent internal scouring.•Fibrous roots form root nets around sandbars, inhibiting external erosion.•The stabilizing effect of vegetation roots becomes more pronounced with increasing discharge. Studies of fluvial geomorphology should consider the essential roles played by plant communities, in addition to the usual geological and hydrological factors. Mobile-bed flume experiments were undertaken to investigate the effects of vegetation roots on the protection of sandbars from erosion in fluvial channels. Loose sandbars (i.e., containing only sand) and sandbars covered with taproot and fibrous-root vegetation types were used to assess the influence of vegetation on residual sandbar volume and channel erosion in the case of emergent, partly submerged, and submerged sandbars. Results indicate that vegetation roots effectively increase soil cohesion, reducing flow scouring. Fibrous root systems form a root net around sandbars, preventing morphological damage caused by external erosion at low flow rates. Taproots develop solid erosion-inhibiting structures within sandbars through their strong primary and lateral roots, effectively preventing internal scouring at high flow rates. Relative to loose sandbars, vegetated sandbars were 24 %, 121 %, and 222 % more protected from sediment erosion under emergent, partly submerged, and submerged conditions, respectively. The ratio of effective erosion protection increased with increasing discharge, with vegetation roots playing a key role in stabilizing sandbars, particularly under submerged conditions.