Measurements of profile change and cross-shore sand flux over the shoreface at Mangawhai Beach, North Island, New Zealand 

Hicks, D. M. 

 

 

 

Chapter in book 

A sea-sled equipped with tilt sensors and bedform-digitising wheel was used to monitor sand levels and to infer cross-shore sand fluxes over the shoreface at Mangawhai Beach on New Zealand's northeast coast. Sixteen profiles were surveyed along a 500 m swath of shore while the beach first accreted then eroded. Repeat runs and measurements against reference rods showed that the sand levels fixed by the sled were accurate to ± 1-2 cm. The track of the sled over or through bedforms sometimes induced a bias in the true local mean bed level. If uncorrected, this would have resulted in often substantial errors in the sand volume change integrated across the profile. Net changes in sand volume under profiles and cross-shore sand fluxes inferred from profile changes varied alongshore due to 2-d transport processes and local topography. When averaged over the swath of profiles, however, the overall change in sand volume on the shoreface was negligible and the cross-shore fluxes inferred from an averaged profile were consistent with a closed 1-d exchange of sand across the shoreface 

 

beach profiles; bedforms; sediments; new zealand; beaches; Biogeophysical