Coastal SEES Collaborative Research: Multi-scale modeling and observations of landscape dynamics, mass balance, and network connectivity for a sustainable Ganges-Brahmaputra delta

世界各地的河流三角洲正处于适度到严重下降的状态，主要是由于人为活动，如筑坝、广泛的堤坝系统、地下水和天然气开采以及强烈的土地利用压力。这些环境也是世界上最具活力的环境之一，受到海平面上升和下降、河流洪水、河道侵蚀和风暴的影响。这种脆弱性在人口稠密的三角洲体系中进一步放大，尤其是在从巴基斯坦到中国等政治敏感地区环绕亚洲沿海的大型巨型三角洲。这些环境不仅因为更多的人类、基础设施和生计处于危险之中而受到影响，而且还因为大量人口对物理和生态支持系统造成的人为压力而受到影响。在孟加拉国和印度的西孟加拉邦，恒河-雅鲁藏布江-梅格纳三角洲(GBMD)可能是世界上最大、人口最密集的三角洲体系的典型例子，在路易斯安那州的面积上容纳了1.5亿人。在这个Coastal Sees项目中，一群拥有多个地球科学和工程学科专业知识的学者聚集在一起，回答有关GBMD及其人类群体的命运和未来可持续性的问题。具体地说，三角洲是否有足够的河流沉积物来跟上海平面上升到2100的步伐？三角洲的河流和潮汐河道网络如何有效地将水和泥沙分配到整个地区？人类活动如何影响这个渠道-网络系统，以及随后对人类基础设施的影响是什么？为回答这些问题而开发的基于研究的知识如何有助于其他地方可持续的GBMD和三角洲的规划和决策？为了解决这些问题，该项目将创新的量化工具(数值模拟、网络和连通性分析)与新的和现有的观测数据相结合，以分析人-自然耦合系统和GBMD的长期可持续性。具体地说，小组成员将(1)制定三角洲范围沉积物扩散的详细质量平衡；(2)定量分析分散沉积物的三角洲系统网络的连通性；(3)通过在地方到全球尺度上的数值模拟整合这方面的知识；(4)利用景观和航道动力学的观测数据，了解海陆耦合作用；(5)评估区域土壤和水资源的质量及其与物理和人为过程的联系；(Vi)评估这些三角洲动态对人类环境和交通的影响，最后(Vii)通过学生、研究人员和专业人员的各种教育活动和机会传播这一知识。小组成员与孟加拉国的当地实体和大学进行了广泛的合作；通过这些联系，该项目中形成的知识将传给相关的利益攸关方社区。对于指导正在进行的改善孟加拉国沿海地区稳定性的大规模工程努力来说，这些发现尤其紧迫。最终产品将提供一个扎实的、综合的和多学科的视角，了解世界上最大的三角洲是如何运作的，以及它在下个世纪对环境变化的合理反应。这个项目中的一些国际活动部分得到了OISE全球风险基金的小额捐款的支持。

River deltas around the world are in a state of modest to severe decline, primarily in response to anthropogenic activities such as the damming of rivers, extensive embankment systems, groundwater and gas extraction, and intense land-use pressures. These settings are also among the world's most physically dynamic, being impacted by sea-level rise and subsidence, river flooding, channel erosion, and storms. Such vulnerabilities are further magnified in highly populated delta systems, notably the large mega-deltas that rim Asian coasts in politically sensitive regions from Pakistan to China. These environments suffer not only from having more humans, infrastructure, and livelihoods in peril, but also from the anthropogenic strain that large populations place on physical and ecological support systems. In Bangladesh and West Bengal, India, the Ganges-Brahmaputra-Meghna delta (GBMD) may well be the prime example as the world's largest and most densely populated delta system, hosting 150 million people in an area the size of Louisiana. In this Coastal SEES project, a diverse group of scholars with expertise across several earth-science and engineering disciplines are brought together to answer questions about the fate and future sustainability of the GBMD and its human population. Specifically, is there sufficient river sediment available for the delta to keep pace with sea-level rise to 2100? How does the delta's network of river and tidal channels effectively distribute water and sediment across the region? How are human activities affecting this channel-network system, and what are the subsequent repercussions on human infrastructure? How can research-based knowledge developed in response to these questions help with planning and decision making for a sustainable GBMD and deltas elsewhere? To address these questions, the project combines innovative quantitative tools (numerical modeling, network and connectivity analysis) with new and existing observational data to analyze the coupled human-natural system and long-term sustainability of the GBMD. Specifically, team members will (i) develop a detailed mass balance for delta-wide sediment dispersal; (ii) quantitatively analyze the connectivity of the delta-system network that disperses this sediment; (iii) integrate this knowledge through numerical modeling at local to global scales; (iv) use observational data of landscape and channel dynamics to understand coupled land-sea interactions; (v) evaluate the quality of regional soil and water resources and their links with physical and anthropogenic processes; (vi) assess the impact of these delta dynamics on the human environment and transportation, and finally (vii) disseminate this knowledge through a variety of educational activities and opportunities for students, researchers, and professionals. Team members have collaborated extensively with local entities and universities in Bangladesh; through these contacts the knowledge developed in this project will reach relevant stakeholder communities. Findings are especially urgent to guide large-scale engineering efforts underway to improve the Bangladesh coastal-zone stability. Final products will provide a grounded, integrated, and multidisciplinary view of how the world's largest delta works and its plausible responses to environmental change in the coming century.Some of the international activities in this project are partially supported by a small contribution from the OISE Global Venture Fund.