Projecting of wave height and water level on reef-lined coasts due to intensified tropical cyclones and sea level rise in Palau to 2100
Projecting of wave height and water level on reef-lined coasts due to intensified tropical cyclones and sea level rise in Palau to 2100
复制标题
DOI：
10.5194/nhess-18-669-2018
复制
发表时间：
2018-03
影响因子：
4.6
通讯作者：
Chuki Hongo;H. Kurihara;Y. Golbuu
中科院分区：
文献类型：
--
作者：
Chuki Hongo;H. Kurihara;Y. Golbuu
抽象。热带气旋（TC）和海平面上升（SLR）造成的主要问题，包括海滩侵蚀，盐水侵入地下水，并破坏沿海地区的基础设施。由于未来的气候变化和当地因素，预计损害的规模和范围将增加。珊瑚礁的向上生长因其作为天然防波堤的作用而受到关注，减少了自然灾害对沿海社区的风险。然而，在强化TC和SLR的条件下，对沿海珊瑚礁风险变化的预测很难量化。在这项研究中，我们预计到2100年在帕劳群岛Melekeok礁的波高和水位，根据波浪模拟在强化TC（在外海洋的有效波高：SWHO = 8.7-11.0 m;在外海洋的有效波周期：SWPo = 13-15 s）和SLR（0.24-0.98 m）。为了了解向上生长的珊瑚礁对波高和水位降低的影响，模拟了两种珊瑚礁条件情景：退化的珊瑚礁和健康的珊瑚礁。此外，根据钻取的岩心对珊瑚礁生长情况进行的分析，提供了对珊瑚群落和珊瑚礁生长率的评估，这是减少热带气旋和SLR对沿海地区造成的风险所必需的。根据我们的计算，在加强TC和SLR到2100年，在礁滩的有效波高（SWHr）将增加从1.05-1.24米，现在的2.14米，如果珊瑚礁退化。同样，到2100年，如果珊瑚礁退化，海岸线的水位将从目前的0.86-2.10米增加到1.19-3.45米。这些预测的变化可能会导致海滩侵蚀，盐水侵入地下水，并破坏基础设施，因为沿海村庄位于目前平均海平面以上1.33米。这些研究结果意味着，即使SWHR下降只有0.1米的珊瑚礁向上生长，它可能会降低海岸损害的风险。我们的研究结果表明，一个健康的珊瑚礁将减少最大0.44米的SWHr。根据钻取的岩心分析，伞房状鹿角珊瑚将是降低风险的关键，到2100年，将需要2.6-5.8公斤CaCO 3 m−2 yr−1，相当于> 8%的珊瑚覆盖，以保持健康的珊瑚礁。这项研究强调，在未来保持珊瑚礁的生长（作为珊瑚覆盖的功能）是有效的，以减少由波浪作用引起的海岸破坏的风险。虽然本研究的重点是Melekeok边缘礁，但许多珊瑚礁在强化TC和SLR条件下处于相同的情况，因此本研究的结果适用于其他礁。这些研究对于指导小岛屿国家以及发展中国家和发达国家的防灾政策的制定至关重要。
Abstract. Tropical cyclones (TCs) and sea level rise (SLR) cause major problems including beach erosion, saltwater intrusion into groundwater, and damage to infrastructure in coastal areas. The magnitude and extent of damage is predicted to increase as a consequence of future climate change and local factors. Upward reef growth has attracted attention for its role as a natural breakwater, reducing the risks of natural disasters to coastal communities. However, projections of change in the risk to coastal reefs under conditions of intensified TCs and SLR are poorly quantified. In this study we projected the wave height and water level on Melekeok reef in the Palau Islands by 2100, based on wave simulations under intensified TCs (significant wave height at the outer ocean: SWHo = 8.7–11.0 m; significant wave period at the outer ocean: SWPo = 13–15 s) and SLR (0.24–0.98 m). To understand effects of upward reef growth on the reduction of the wave height and water level, the simulation was conducted for two reef condition scenarios: a degraded reef and a healthy reef. Moreover, analyses of reef growth based on a drilled core provided an assessment of the coral community and rate of reef production necessary to reduce the risk from TCs and SLR on the coastal areas. According to our calculations under intensified TCs and SLR by 2100, significant wave heights at the reef flat (SWHr) will increase from 1.05–1.24 m at present to 2.14 m if reefs are degraded. Similarly, by 2100 the water level at the shoreline (WLs) will increase from 0.86–2.10 m at present to 1.19–3.45 m if reefs are degraded. These predicted changes will probably cause beach erosion, saltwater intrusion into groundwater, and damage to infrastructure, because the coastal village is located at ∼ 3 m above the present mean sea level. These findings imply that even if the SWHr is decreased by only 0.1 m by upward reef growth, it will probably reduce the risks of costal damages. Our results showed that a healthy reef will reduce a maximum of 0.44 m of the SWHr. According to analysis of drilled core, corymbose Acropora corals will be key to reducing the risks, and 2.6–5.8 kg CaCO3 m−2 yr−1, equivalent to > 8 % of coral cover, will be required to keep a healthy reef by 2100. This study highlights that the maintaining reef growth (as a function of coral cover) in the future is effective in reducing the risk of coastal damage arising from wave action. Although the present study focuses on Melekeok fringing reef, many coral reefs are in the same situation under conditions of intensified TCs and SLR, and therefore the results of this study are applicable to other reefs. These researches are critical in guiding policy development directed at disaster prevention for small island nations and for developing and developed countries.