Trapping of fine-grained sediment on a supply-limited intertidal shore platform at Kaikoura, New Zealand

Shore platforms are generally supply-limited environments and few studies have attempted to measure sediment transport within this rock coast setting. This paper summarises a field-based pilot study that successfully collected fine-grain sediment moving across a sub-horizontal platform at Mudstone Bay, Kaiko over bar ura, New Zealand. Two large-aperture and two small-aperture Time-Integrated Mass-sediment Samplers (TIMS) were deployed for 9-days, encompassing 2 days of storm conditions (offshore significant wave heights between 2.0 and 3.6 m, with sediment trapped in both landward and seaward facing directions. The net flux of sediment captured in large aperture samplers was greatest in a seaward-direction (15.2 g), whereas the narrow-mouth samplers, that principally collected suspended sediment had a net onshore flux (5.4 g). The sediment traps yielded sufficient sample to undertake geochemical and textural analysis. Interpretation of these data suggests that the origin of transported material was autochthonous to the platform, being >80 % silt-sized and compositionally consistent with material derived from the shore platform and/or cliff colluvium. This pilot experiment demonstrates that mass-sediment samplers can be used in supply-limited intertidal shore platform settings. Further research involving greater sampling frequency and duration and concomitant detailed hydrodynamic measurements are likely to reveal important insights into the erosion environment.

Automated summary

This paper summarises a field-based pilot study that successfully collected fine-grain sediment moving across a sub-horizontal platform at Mudstone Bay, New Zealand. The study found that sediment transport on the platform is directional and likely originates from the platform itself. Further research is needed to gain a better understanding of the erosion environment.