Coastal Erosion Prevention with Nature-Inspired Geotechnics

Abstract

Around 80% of Australian residents live near its beautiful coastline. Unfortunately, coastal land and infrastructure are at a greater risk than ever due to the unprecedented increase in coastal erosion rates driven by the climate change-induced rise in the mean sea level (MSL). Traditional erosion control measures, such as mechanical compaction, cement-based structures, synthetic binders, and soil replenishment, struggle to meet modern sustainability demands. In contrast, natural beach rocks exhibit remarkable resistance to erosion, formed through complex processes involving nearshore microbial life. The nearshore microbial life produces macromolecules of the polymeric substances that capture the metals and precipitate stable crystal units upon the availability of nutrients under specific conditions, forming erosion-resistant beach rocks. Such beach rocks in nature take years to decades to form through numerous complex geochemical pathways. It is not only critical to unpin these geochemical reactions but also to engineer them to expedite the rates of formation.

This study explores the microbial ureolytic pathway of crystal precipitation, often termed biocementation, and its potential for coastal erosion mitigation. In this study, the scaled wave action was simulated in a flume, and the biopolymer-biocement composite treatment was compared for its performance against erosion control with the trending plain biocement and biopolymer treatments. The study also devised a biopolymer-biocement composite mimicking the natural phenomena and compared it with the plain biocement and plain biopolymer routes of soil improvement. The cost and environmental impact of the treatments are accounted for. Findings indicate that plain biocementation leads to brittle failure under coastal waves, and biopolymer protection wears off quickly upon hydration. Both treatments only delay erosion beyond a certain wave energy threshold. In contrast, the biopolymer-biocement composite provides dual protection: dampening wave forces with the viscous biopolymer matrix and offering binding strength with brittle biocement. This composite treatment costs about half as much as an equally erosion-resistant plain biocemented sample and produces 50% less ammonia. This study elucidates the resilience mechanisms of beach rocks and proposes a promising methodology for field-scale testing. The research contributes to geotechnical and geoenvironmental engineering by offering nature-inspired solutions for coastal infrastructure conservation.