Coastal erosion is a phenomenon of long-term loss of beach materials (landmass) from the shore, eroded sediments encroached by waves and currents transported in its net transport direction. Net transport characterised as longshore sediment transport and cross-shore sediment transport. Longshore sediment transport chains with the effect of longshore currents but the cross-shore sediment transport mainly associated with wave characteristics and seabed slope. To militate the cross-shore erosion, effective longshore protection to designed either with a shore structure or with a submerged reef structure. Shore-based protection is not much benefit for cross-shore erosion, Submerged reef-based structures are more effective over cross-shore erosion, But the competent role of a reef structure exists based on the relative depth of submergence and the amount of energy transmitted for design wave parameters. Hence a reef structure is designed with geo-tubes and gabion box for cross-shore erosion-prone coastal zone of south India. This paper presents the design and hydrodynamic stability of model scale 1:10 three number of geo-tubes of two-layer shielded with gabion box reef structure. Experiments were conducted to optimize the depth of submergence with a most probable hydrodynamic performance of the designed reef structure. The model study also includes estimates of the wave transmission in order to ensure adequate hydrodynamic characteristics of the reef structure. The model base width is 1.12m, a crest width of 0.2m and height of reef as 0.36m. The test performed for two different water depth such as 0.4 m, and 0.5 m, wave height of 0.1 m, 0.15 m 0.2 m, and 0.25 m, wave period range of 0.6s to 2.5s. The physical model studies are checked out in a 2 m wide 2 m deep 72 m long flume in the department of ocean engineering at Indian Institute of Technology Madras. The results are analyzed, irrespective of stability and hydrodynamic characteristics.
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