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: 1737221
• 负责人: Steven Kuehl
• 金额: $ 30.87万
• 依托单位: College of William & Mary Virginia Institute of Marine Science
• 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 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1737221&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.

十亿人口生活在河流三角洲，由于地面沉降加剧、增长率下降和海平面加速上升，其中许多地区现在被认为面临风险。这些沿海地区的土地下沉大大增加了风暴潮和洪水的威胁。 例如，2008 年，纳尔吉斯气旋席卷缅甸伊洛瓦底江三角洲，造成 138,000 多人死亡，2015 年同一地区的强季风降雨导致低洼地区发生洪水，导致 20 万人流离失所。为了了解和预测河流三角洲的未来演化，有必要了解河流中的沉积物如何被输送并输送到三角洲的陆上和近海区域，因为这是三角洲形成的物质。 该项目将帮助人们了解缅甸的伊洛瓦底江-萨尔温江 (I-S) 三角洲，这可能是地球上仅存的最后一个主要三角洲系统，但我们对其缺乏完整的了解。 具体来说，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 5000 万人居住的敏感三角洲环境的未来发展提供信息，并丰富我们对全球三角洲的常识。 该项目还将涉及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，为与美国同行的培训和合作提供机会。I-S 系统每年携带的估计 600 公吨河流沉积物中的大部分是输送到安达曼海北部广阔的大陆架，该大陆架受到强潮、季风条件和周期性气旋的影响；然而，这种材料的命运未知。现有的测深数据和稀疏的初步调查暗示了大陆架水下三角洲的发育模式，这与之前研究的其他主要三角洲形成鲜明对比。特别是，陆架的表面形态和沉积物结构呈现出显着的双边（东西）不对称性：伊洛瓦底江东部河口有一个缓坡的沙质坡道，而邻近西部的泥质内陆架到中部的斜坡则呈现出明显的不对称性。马尔塔班湾。基于实地和建模的实验将使研究团队能够对比海洋分类、运输过程和底层构造在创造这种不寻常的三角洲表现中的相对作用。地球物理观测、取芯和实验室研究将详细说明全新世的结构，并量化全新世和陆架上最近沉积物的数量、来源和分布。为了探索沉积物从河流源头到沉积汇的输送路径，将使用数值模型来解释河流输入、波浪、潮汐和风驱动的水流对沿海海洋内河流沉积物扩散的影响。 模型运行将代表东南季风和西北季风期间以及高流量期间的条件。该模型还将用于利用气旋产生的波浪和风场的表示来探索在大风暴期间增强运输的潜力。