Abstract
Co-seismic uplift of the Kaikoura Peninsula emerged the shore platform at Mudstone Bay upwards by 0.96 m, transforming the formerly intertidal platform. The post-uplift morphology now contains -90 m of a supratidal zone that represents an incipient marine terrace that has the potential to be preserved in the geological record. This paper investigates wave conditions that drive supratidal inundation, thereby influencing post-uplift terrace development processes. Wave hydrodynamics during austral summer and winter under moderately energetic offshore conditions showed that only 24 % of swell energy propagated to the inner platform compared to 84 % during fair weather swell. Infragravity energy increased inland during storms and dominated the energy spectra (70 %) on the incipient marine terrace. Wave attenuation increased under storm conditions as the effective intertidal width elongated and merged with the incipient marine terrace. Wave propagation under higher energy conditions (offshore significant wave heights of 3.5 m) were sufficient to partially inundate the supratidal terrace up to 9 cm in water depth but only for 2 h. Storm waves when congruent with high tide were used to develop a frequency model of inundation, which suggests that for the post-uplift period 13 % of tides could inundate portions of the supratidal terrace, but full inundation to the cliff toe occurs for <0.05 % of tides. Hence, the new supratidal marine terrace is vulnerable to inundation from annual storm events but protects the cliff toe from wave action.