Collaborative Research: Fate of Irrawaddy and Salween River Sediment: Relative Importance of Oceanographic and Tectonic Controls

合作研究：伊洛瓦底江和萨尔温江沉积物的命运：海洋学和构造控制的相对重要性

• 批准号: 1737287
• 负责人: Jingpu (Paul) Liu
• 金额: $ 21.47万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-15 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1737287&HistoricalAwards=false
• 关键词: Collaborative; Research; Fate; Irrawaddy; Salween

Half a billion humans live on river deltas, and many of these areas are now considered at risk as a result of increasing land subsidence, decreasing growth rate, and accelerating sea-level rise. Sinking land in these coastal areas greatly increases the threat from storm surge and flooding. For example, Cyclone Nargis tracked across the Irrawaddy delta in Myanmar in 2008 resulting in over 138,000 fatalities, and heavy monsoon rains in this same area in 2015 displaced 200,000 people as a result of flooding in low lying areas. To understand and predict the future evolution of river deltas, it is necessary to know how sediment from the river is transported and delivered to the onshore and offshore regions of the delta, as this is the material from which deltas arise. This project will provide an understanding of the Irrawaddy-Salween (I-S) delta in Myanmar, perhaps the Earth's last remaining major delta system for which we lack a complete picture. Specifically, the project will examine the tectonic and oceanographic factors that control the delivery of sediment, and the present pattern and rates of delta growth. This results of this study will inform the future development of a sensitive deltaic setting home to 50 million people, and add to our general knowledge of deltas worldwide. The project will also involve the mentoring and training of US undergraduate and graduate students, and will engage Myanmar scientists and students, providing opportunities for training and collaboration with US counterparts.Much of the estimated 600 Mt of river sediment carried by the I-S system annually is delivered to a wide continental shelf in the northern Andaman Sea that is influenced by strong tides, monsoon conditions, and periodic cyclones; however the fate of this material is unknown. Existing bathymetric data and sparse initial surveys hint at a mode of subaqueous delta development on the shelf which contrasts markedly from other previously studied major deltas. In particular, the shelf exhibits a dramatic bilateral (east-west) asymmetry of the surface morphology and sediment texture: a gently sloping sandy ramp off the eastern mouths of the Irrawaddy, and a muddy inner- to mid-shelf clinoform in the adjacent western Gulf of Martaban. Field- and modeling-based experiments will enable the research team to contrast the relative roles of oceanographic sorting, transport processes, and underlying tectonics in creating this unusual deltaic expression. Geophysical observations, coring and laboratory studies will detail the architecture and quantify the amounts, source, and distribution of Holocene and recent sediment accumulating on the shelf. To explore transport pathways of sediment from the fluvial source to depositional sinks, a numerical model will be used to account for the effects of river input, waves, tidal- and wind-driven currents on the dispersal of river sediment within the coastal ocean. Model runs will represent conditions during the SE and NW monsoons, and during times of high discharge. The model will also be used to explore the potential for enhanced transport during large storms using representations of the cyclone-generated wave and wind field.

5亿人生活在河流三角洲上，其中许多地区现在被认为处于危险之中，原因是地面沉降增加，增长率下降，海平面加速上升。这些沿海地区的土地下沉极大地增加了风暴潮和洪水的威胁。例如，2008年飓风纳尔吉斯横扫缅甸伊洛瓦底江三角洲，造成超过13.8万人死亡，2015年该地区的季风雨导致20万人因低洼地区的洪水而流离失所。为了了解和预测河流三角洲未来的演变，有必要了解河流中的沉积物是如何被输送和输送到三角洲的陆上和近海地区的，因为这是三角洲形成的物质来源。这个项目将提供对缅甸伊洛瓦底-萨尔温(i-S)三角洲的了解，这可能是地球上最后一个我们缺乏完整图景的主要三角洲体系。具体地说，该项目将研究控制沉积物输送的构造和海洋因素，以及目前三角洲增长的模式和速度。这项研究的结果将为拥有5000万人口的敏感三角洲环境的未来发展提供信息，并增加我们对全球三角洲的普遍了解。该项目还将包括对美国本科生和研究生的指导和培训，并将吸引缅甸科学家和学生参与，为培训和与美国同行合作提供机会。I-S系统每年携带的约600公吨河流沉积物中的大部分被输送到受强潮、季风条件和周期性龙卷风影响的安达曼海北部的一个宽阔的大陆架；然而，这种材料的命运尚不清楚。现有的水深数据和稀少的初步调查表明，陆架上存在一种水下三角洲的发育模式，这与以前研究的其他主要三角洲形成了鲜明的对比。特别是，大陆架的表面形态和沉积物结构呈现出戏剧性的两侧(东西)不对称：伊洛瓦底江东部入海口附近缓缓倾斜的沙质坡道，以及邻近的马拉班湾西部陆架内部到中部的泥泞床形。基于现场和模型的实验将使研究小组能够对比海洋分类、运输过程和底层构造在创造这种不寻常的三角洲表达中的相对作用。地球物理观测、取心和实验室研究将详细描述全新世和最近沉积在陆架上的结构，并量化其数量、来源和分布。为了探索泥沙从河流源头到沉积汇的输送路径，将使用一个数值模型来考虑河流输入、波浪、潮汐和风力驱动的水流对河流沉积物在沿海海洋中扩散的影响。模型运行将代表东南季风和西北季风期间以及高流量时期的情况。该模型还将被用来利用气旋产生的海浪和风场的表示来探索在大风暴期间加强运输的潜力。

项目成果

Sediment dispersal and accumulation off the Ayeyarwady delta – Tectonic and oceanographic controls

• DOI: 10.1016/j.margeo.2019.106000
• 发表时间: 2019-11
• 期刊: Marine Geology
• 影响因子: 2.9
• 作者: S. Kuehl;Joshua R. Williams;J. Liu;C. Harris;D. W. Aung;D. Tarpley;Mary Goodwyn;Y. Aye

Fate of Ayeyarwady and Thanlwin Rivers Sediments in the Andaman Sea and Bay of Bengal

• DOI: 10.1016/j.margeo.2020.106137
• 发表时间: 2020-05
• 期刊: Marine Geology
• 影响因子: 2.9
• 作者: J. Liu;S. Kuehl;A. Pierce;Joshua R. Williams;N. Blair;C. Harris;D. W. Aung;Y. Aye