Reef islands are some of the most highly sensitive landforms to the impacts of future environmental change. Previous assessments of island morphodynamics primarily relied on historical aerial and satellite imagery. These approaches limit analysis to two-dimensional parameters, with no ability to assess long-term changes to island volume or elevation. Here, we use high-resolution airborne LiDAR data to assess three-dimensional reef island features for 22 islands along the north-western coast of Australia. Our primary objective was to utilize two regional LiDAR datasets to identify characteristics indicative of island sensitivity and future vulnerability. Results show reef platform area to be an accurate predictor of island area and volume suggesting larger island volumes may reflect (1) increased carbonate production and supply from the reef platform and/or (2) enhanced shoreline protection by larger reef platforms. Locations of foredune scarping (an erosional signature) and island orientations were aligned to the regional wind and wave climate. Reef island characteristics (island area, volume, elevation, scarping, and platform area) were used to rank islands according to sensitivity, using a new Island Sensitivity Characteristics Index (ISCi) where low ISCi indicates stable islands (large areas and volumes, high elevations, and fewer scarped areas) and high ISCi indicates unstable islands (small areas and volumes, low elevations, and more scarped areas). Comparison of two LiDAR surveys from 2016 and 2018 validates the use of 3D morphometrics as important (direct) measurements of island landform change, and can complement the use of 2D parameters (e.g., area) moving forward. Results demonstrate that ongoing use of airborne LiDAR and other 3D technology for monitoring coral reef islands at regional scales will enable more accurate quantification of their sensitivity to future impacts of global environmental change.

中文翻译：

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基于LiDAR形态学指标的珊瑚礁岛敏感性评估

礁岛是对未来环境变化影响最敏感的地貌。先前对岛屿形态动力学的评估主要依赖于历史的航空和卫星图像。这些方法将分析限制在二维参数上，无法评估岛量或高程的长期变化。在这里，我们使用高分辨率的机载LiDAR数据来评估澳大利亚西北海岸22个岛屿的三维礁岛特征。我们的主要目标是利用两个区域LiDAR数据集来识别表明岛屿敏感性和未来脆弱性的特征。结果表明，礁石平台面积是岛屿面积和体积的准确预测指标，表明较大的岛屿体积可能反映（1）礁石平台碳酸盐产量和供应量的增加和/或（2）更大的礁石平台对海岸线的保护作用。前陆剥皮（侵蚀特征）和岛屿方向的位置与区域风浪气候一致。使用新的岛屿敏感度特征指数（ISCi），使用礁岛特征（岛屿面积，体积，高度，起伏和平台面积）根据敏感性对岛屿进行排名，其中低ISCi表示稳定的岛屿（大面积和体积，高海拔） ，缺少的痕迹的区域更少）和较高的ISCi表示不稳定的岛屿（面积和容积小，海拔低且有更多痕迹的区域）。通过比较2016年和2018年的两次LiDAR调查，可以验证3D形态计量学是对岛地貌变化的重要（直接）测量结果，并且可以补充2D参数（例如面积）的使用。结果表明，持续使用机载LiDAR和其他3D技术在区域范围内监视珊瑚礁岛将能够更准确地量化其对全球环境变化的未来影响的敏感性。