Submergence and Wave Action Resilience of Vetiver Grass Protected Fly Ash Amended Soil Slopes

This study aims to investigate the durability of vegetated slopes using vetiver grass (Vetiveria zizanioides), constructed with fly ash-amended soil (FAS) against submergence and wave action in swampy areas. Four model slopes were fabricated using soil (silty sand, ϕ = 28°) of swampy area, and stabilizing the soil with 8.5% (w/w) fly ash. Slopes of two models were vegetated with vetiver, while one model had its slope protected with jute-geotextile. After 172 days of fabrication, slopes were submerged for 5 days, and then subjected to wave action of 0.2–0.3 m/s velocity. The maximum shoot and root length of vetiver varied within 130–170 cm and 61–74 cm, respectively. FAS with jute-geotextile increased the number of tillers and vegetation-covered areas subsequently by 2.0 and 2.4 times. Vetiver increased the slope durability 15 times longer with 19% less soil loss than that of the bare slope model. Resilience of the model fabricated with FAS and protected by vetiver enhanced the duration by 2 times through minimizing soil erosion by 12%. However, for the model fabricated with FAS and protected with vetiver and jute-geotextile, the duration was amplified by 3 times with 60% less soil loss than that of the vetiver protected slope. Vetiver enhanced the slope resilience to wave action and submergence. However, vetiver grass along with fly ash and jute-geotextile enhances the resilience of slope to wave action and submergence by improving soil strength, nutrient, microscopic properties; and by reducing permeability, seepage, soil erosion, forming a compatible protection system.