Ecological Appraisal of Geotextiles in Coastal Erosion Protection Engineering

Abstract

Jebakumar, J.P.P.; Nandhagopal, G.; RajanBabu, B.; Ragumaran, S.; Kiran, A.S., and Ravichandran, V., 2022. Ecological appraisal of geotextiles in coastal erosion protection engineering. Journal of Coastal Research, 38(2), 345–354. Coconut Creek (Florida), ISSN 0749-0208. The emergence of geotextiles in coastal erosion protection as an alternative material to stone boulders and concrete tetrapods is evident in the recent past. The submergence of geotextiles being colonized by epibiotic organisms on their surface is called marine growth, similar to all other materials inundated in seawater. It includes organisms of the primary producers of algal populations, secondary consumers, and filter feeders of benthic-fouling communities crusting geotextiles' surface. In-situ experimental studies of more than a year of research at a fishing harbour along Chennai coast, India, projected a typical pattern of epibiotic encrustation and its impact on tensile strength nonwoven geotextiles fabrics. Results demonstrated a patchy-mosaic design of marine growth on the geotextile comprising 41 species of sessile invertebrates, including seaweeds, showing a natural succession of biotic density and diversity. Noted distinct stages in colonization were commencing with the domination of deposit feeders, followed by filter feeders, secondary consumers, and primary producers, where later filter feeders subjugated them. The incidence of fundamental ecological succession based on food availability, nature of trophic consumers, and intra/interspecific competition lead to dynamic population shifts on geotextiles. The monolayer settlement pattern of marine growth on the surface is dominated by the benthic filter-feeding community, forming an inverted trophic pyramid structure. Significant differences in tensile strength between geotextile with and without marine growth (p = 0.042) and the progressive improvement in tensile strength indicated no adverse impact on the erosion protection structure's stability. Thus, a harmonious relationship between population density and tensile strength (r = 0.8) represents a mutual relationship between encrusting biota and geotextile substrate, resulting in camouflaging with the coastal background ecosystems as an innovative ecodesign for coastal erosion protection engineering.