Optimizing beach nourishment composition for coastal protection in Sri Lanka: Insights from flume experiments 

Beach erosion is a significant threat to Sri Lanka’seconomically and ecologically valuable coastlines, particularly along the Southwest and Western regions. Traditional beach nourishment methods, such as use offshore sand are common but have limitations in terms of durability and recurring costs.This study investigates the potential benefits of incorporating crushed waste glass into offshore sand to enhance erosion resistance and cost-effectiveness towards beach nourishment. This study evaluated four materials; native sand, offshores and, river sand, and crushed glass, through controlled hydraulic flume experiments and particle size analysis.Offshore sand was the most susceptibile to erosion with a transported sediment volume of 26%, while crushed glass showed superior stability with only 14% erosion. Blends of offshore sand and crushed glass containing 10–20%crushed glass (CG10–CG20) achieved an optimal balance between durability and material cost. The unique compacting properties and smoother surface texture of crushed glass contributed to reduced sediment mobility under wave action.Furthermore, the study highlighted the environmental benefits of utilising locally available glass waste, promoting sustainable waste management while enhancing coastal resilience. These findings provide practical insights for future beach nourishment projects in Sri Lanka, emphasizing the dual benefits of improved performance and ecological responsibility. Future research should focus on validating these results long-term field settings, assessing ecological impacts, and developing scaling methods for broader coastal management applications.