A regional analysis of tide-surge interactions during extreme water levels in complex coastal systems of Aotearoa New Zealand

Abstract

Tide-surge interaction (TSI) is a critical factor in assessing flooding in shallow coastal systems, particularly in estuaries and harbours. Non-linear interactions between tides and surges can occur due to the water depth and bed friction. Global investigations have been conducted to examine TSI, but its occurrence and impact on water levels in Aotearoa New Zealand (NZ) have not been extensively studied.

Water level observations from 36 tide gauges across the diverse coast of NZ were analysed to determine the occurrence and location of TSI. TSI was found to occur in most sites along the coast of NZ and to have a significant impact on water levels in inner estuarine locations. Therefore, further investment in the tide gauge network is needed to provide more accurate observations to incorporate TSI in flooding hazard projections