Abstract:
Coral reef islands are products of the interaction between hydrodynamics, island morphology, and sediment transport processes (Kench et al., 2009a). These morphodynamic processes have typically been examined in terms of the interaction of waves with the reef edge and reef platform, with less emphasis on the measurements of wave characterisitcs in the nearshore which have greater influence on nearshore sediment transport processes (Beetham and Kench, 2014). This thesis details a study of reef island morphodynamics undertaken on Tepuka Island in Funafuti Atoll, Tuvalu, in which concurrent measurements of nearshore hydrodynamics and beach profile change were taken over a two week period in February 2015. Tepuka was influenced by northerly wind and swell throughout the study period, and this led to a north-south gradient in wave energy along the island. The greatest value of Hmax recorded was 1.24 m, on the northeastern aspect of Tepuka, while at the same time the southern end experienced an Hmax of 0.43 m. Along-shore currents were recorded travelling from north to south irrespective of tidal stage, although there was some reversal in current direction between low and rising tide. Measurements of beach profile change gave a net erosion for all except one of the five transects. The greatest net erosion was recorded at the north end of Tepuka, at -6.04 m2. In addition, sediments were observed to move landward on some parts of the island. Overall, this thesis has shown that the adjustment of shore face topography around Tepuka is highly influenced by the along-shore variations in wave energy.
