西沙永乐环礁岸-坡地貌声学特征精细刻画及其源汇过程定量模拟研究

Abundant of the coral reef landform systems with typical structures are extensively developed in the Xisha area of the South China Sea, where special tectonic setting, hydrodynamic environment and sediment properties have created a unique sediment transport system. Restricted by factors such as insufficient historical data, difficulty of site observation and low precision data, fewer previous studies could consider material source, transport and deposition on the reef shore-slope as a whole system. This project will select Yongle Atoll as the study area and intend to delineate the atoll shore-slope superficial dynamic geomorphology and acoustic characteristics. It will be achieved by three-dimensional space analysis and detailed structure extraction of the atoll shore-slope based on building high-precision DTM model using GIS technology to merge comprehensive acoustic detection data such as multi-beam data, multi-channel seismic data, ADCP data and surface sediment sample analysis data. Through establishment of a coupled numerical model about hydrodynamic and sediment transport in the study area, this project will reconstruct the sediments transport principle form and its evolution process under external force action such of wave, current and gravity. Combining the background analysis of the Xisha area, this study will further interpret the transport mechanism and dominant controlling factors of the fine scale source-to-sink of the Yongle Atoll. All of the studies in this project will provide important theoretical basis and scientific evidence for further studying sediment transport process of the reef material, disaster analysis and prediction, and construction of islands and reefs in South China Sea.

南海西沙海域发育了大量类型众多、结构典型的岛礁地貌，该区特殊的构造背景、水动力环境和沉积物物性塑造了独特的沉积物输运体系。受岛礁区历史资料匮乏、现场观测困难及数据精度不高等因素的制约，前人将岛礁岸-坡物源、运移和沉积作为整体系统开展的针对性研究较少。本申请项目选择永乐环礁区作为研究靶区，拟综合利用多波束数据、多道地震数据、ADCP数据等声学探测资料和表层沉积物样品分析数据,运用GIS技术进行多尺度数据融合，构建高精度无盲区环礁DTM模型，并进行三维空间分析与细观特征提取，精细刻画环礁岸-坡表层动力地貌及浅部结构的声学识别特征；通过建立该区水动力及沉积物运移的耦合数值计算模型，重构波流及重力等内外动力作用下岛礁岸-坡沉积物运移过程。结合西沙海域区域背景分析，揭示永乐环礁小尺度“源-汇”机理与主控因素。本申请项目将为研究岛礁物质输运机理、灾害分析预测和岛礁工程建设提供重要的理论基础和科学依据。

本项目选择永乐环礁区作为研究靶区，综合利用多波束数据、多道地震数据、ADCP数据等声学探测资料和表层沉积物样品分析数据，主要完成了以下研究成果：.（1）.运用GIS技术进行了多尺度数据融合，构建了高精度无盲区环礁DTM模型；.（2）.完成了三维空间分析与细观特征提取，精细刻画了环礁岸-坡表层动力地貌及浅部结构的声学识别特征；.（3）.建立了该区水动力及沉积物运移的耦合数值计算模型，重构了波流及重力等内外动力作用下岛礁岸-坡沉积物运移过程。.（4）.结合西沙海域区域背景分析，揭示了永乐环礁小尺度“源-汇”机理与主控因素。.本项目成果为研究岛礁物质输运机理、灾害分析预测和岛礁工程建设提供了重要的理论基础和科学依据。