基于地面3D激光扫描技术的海南岛南部海岸巨砾沉积研究

Application of the terrestrial laser scanner to the coastal boulders on the southern coast of Hainan Island

海岸巨砾沉积是反映海岸极端波浪事件活动历史的重要载体,对于预测未来海洋极端水文灾害发生趋势具有重要意义。本文基于地面3D激光扫描技术,以海南岛南部海岸大东海和小东海的海岸珊瑚巨砾沉积为研究对象,使用了Riegl VZ4000地面3D激光扫描仪精确测量了这些珊瑚巨砾的体积参数,结合水文模型计算出搬运这些巨砾所需的临界起动波高和流速,重构了极端波浪事件强度,并根据沉积学和动力学对海岸珊瑚巨砾的沉积成因进行了分析。结果表明,地面3D激光扫描技术与传统测量方式相比,具有方便、快速、高精度的优势。海南岛大、小东海堆积的珊瑚巨砾沉积是由台风波浪破碎珊瑚礁平台前缘并将碎块输运到礁平台而成的,且台风的最大强度可能接近超强台风“宝霞”。本研究可为重建南海地区古风暴活动历史,揭示该地台风活动规律以及海岸极端波浪灾害的防风减灾工作提供重要科学参考信息。

Coastal boulders,with durable and easily visible,have been widely used as markers to confirm the existence and estimate the magnitude of marine hydrodynamic extreme events,which is valuable for risk prediction and coastal management.A detailed survey of large boulder accumulations was carried out at Dadonghai and Xiaodonghai sites on the southern coast of Hainan Island.The size,position and distance from the shoreline of 24 boulders were measured by Riegl VZ4000 3D terrestial laser(TLS)scanner and traditional methods,respectively,in order to determine their volume parameters,mass as well as the conditions under which they were transported landward to their present positions.The results were then analyzed with hydrodynamic models to evaluate the characteristics of the transporting waves and flow speeds.Storm waves would be responsible for the detachment and transportation of these largest boulders.The maximum intensity of typhoon hitting this area should not be less than that of super Typhoon Baoxia.The results indicate that the TLS technology has the advantages of convenience,speed and accuracy to measure hydrodynamic process of coastal boulders than that of traditional methods.The study insists on the potential for reconstructing the history of paleostorm activity in the South China Sea and predicting the occurrence trend of marine extreme wave disasters in the coastal areas of Hainan Island in the future.