As highlighted by the Association of State Dam Safety Officials, overtopping is a prevalent cause of earthen dam failures and has caused many flood-related damages. Reducing sediment erodibility is critical to mitigate the risk of overtopping-induced breaching. Traditionally, sediment properties are improved mechanically or chemically. However, chemical additives have drawbacks, such as altering soil properties or introducing toxicity. Recent studies have focused on using biopolymers, like Xanthan gum, to enhance sediment properties with limited adverse effects. While geotechnical tests have shown that biopolymers can bolster soil strength, biopolymer impact on soil erodibility and resistance in real-world conditions remains uncertain. Experiments were conducted at the University of South Carolina Hydraulics Laboratory to investigate erodibility of Xanthan gum-treated sand and its relation to flow velocity. Factors examined included optimal water content, biopolymer concentration, average flow velocity, and erosion rate. Xanthan gum was chosen for its availability, affordability, and ease of application. Sample preparation involved the addition of 0.05% - 0.5% biopolymer by mass to dry sand. Biopolymer and sand were thoroughly mixed to obtain a mixture with water content equal to the optimal value. Results suggest that optimal water content of sand-xanthan gum mixtures increases with biopolymer concentration. Erodibility of xanthan gum-treated sand increases with flow velocity and is reduced by increasing biopolymer concentration. Finally, increasing xanthan gum concentration results in a change in sediment transport mode, from standard bedload in loose sand to erosion and transport of chunks of treated sand.
