Mangawhai-Pakiri: Sustainability of Coastal Sand Extraction from a Near-shore Bar

Beach foreshore profile monitoring is often utilised to determine whether a beach is eroding or accreting. For beaches which cycle sediment between the foreshore and the near-shore bar, such assessments cannot be carried out with any degree of certainty without understanding of the coastal processes and sediment movements applicable to the location. A vital component of this is an investigation into the relationship between measured changes in foreshore sand volumes and the occurrence of significant onshore storm events. Post-storm beach rebuild can then be estimated and subtracted from the monitoring results thus allowing a more accurate assessment of net foreshore sediment surpluses or deficits. The above procedure is presented here and was used in a study to determine short-term sustainable limits for sand extraction from the near-shore bar of Mangawhai and Pakiri Beaches on the Northland East Coast of New Zealand.