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. Statistical analysis and numerical modelling were conducted on data from both inside and outside estuaries, focusing on one estuary (Manukau Harbour) to determine the impact of TSI and estuarine morphology on the co-occurrence rate of extreme events. TSI was found to occur at most sites in NZ and primarily affects the timing of the largest surges relative to high tide. There were no regional patterns associated with the tide, non-tidal residual, or skew-surge regimes. The strongest TSI occurred in inner estuarine locations and was correlated with the intertidal area. The magnitude of the TSI varied depending on the method used, ranging from -16 cm to +27 cm. Co-occurrence rates of extreme water levels outside and inside the same estuary varied from 20% to 84%, with TSI modulating the rate by affecting tidal amplification. The results highlight the importance of investing in a more extensive tide gauge network to provide longer observations in highly populated estuarine coastlines. The incorporation of TSI in flooding hazard projections would benefit from more accurate and detailed observations, particularly in estuaries with high morphological complexity. TSI occurs in most sites along the coast of NZ and has a significant impact on water levels in inner estuarine locations. TSI modulates the co-occurrence rate of extreme water levels in estuaries of NZ by affecting tidal amplification. Therefore, further investment in the tide gauge network is needed to provide more accurate observations to incorporate TSI in flooding hazard projections.

中文翻译：

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新西兰 Aotearoa 复杂沿海系统极端水位期间潮涌相互作用的区域分析

潮汐-浪涌相互作用 (TSI) 是评估浅水沿海系统洪水的关键因素，尤其是在河口和港口。由于水深和床摩擦，潮汐和浪涌之间可能发生非线性相互作用。已开展全球调查以检查 TSI，但其发生及其对新西兰奥特罗瓦 (NZ) 水位的影响尚未得到广泛研究。对来自新西兰不同海岸的 36 个验潮仪的水位观测值进行了分析，以确定 TSI 的发生和位置。对河口内外数据进行统计分析和数值建模，重点研究一个河口（Manukau Harbour），以确定TSI和河口形态对极端事件共现率的影响。TSI 被发现发生在新西兰的大多数地点，主要影响相对于涨潮的最大浪涌的时间。没有与潮汐、非潮汐残余或偏斜浪涌状态相关的区域模式。最强的 TSI 发生在河口内部位置，并与潮间带区域相关。TSI 的大小因所使用的方法而异，范围从 -16 厘米到 +27 厘米。同一河口内外极端水位的同时发生率从 20% 到 84% 不等，TSI 通过影响潮汐放大来调节发生率。结果突出了投资于更广泛的潮汐测量网络以在人口稠密的河口海岸线提供更长时间观测的重要性。将 TSI 纳入洪水灾害预测将受益于更准确和详细的观察，特别是在形态复杂性高的河口。TSI 发生在新西兰沿岸的大部分地点，并对河口内陆地区的水位产生重大影响。TSI 通过影响潮汐放大来调节新西兰河口极端水位的共现率。因此，需要进一步投资潮汐测量网络，以提供更准确的观测结果，将 TSI 纳入洪水灾害预测。TSI 通过影响潮汐放大来调节新西兰河口极端水位的共现率。因此，需要进一步投资潮汐测量网络，以提供更准确的观测结果，将 TSI 纳入洪水灾害预测。TSI 通过影响潮汐放大来调节新西兰河口极端水位的共现率。因此，需要进一步投资潮汐测量网络，以提供更准确的观测结果，将 TSI 纳入洪水灾害预测。