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中度至严重衰退的状态，这主要是由于人为活动，如在河流上筑坝、广泛的堤防系统、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物理活力的环境之一，受到海平面上升和下沉、河流洪水、河道侵蚀和风暴的影响。在人口密集的三角洲系统中，这种脆弱性进一步被放大，尤其是在从巴基斯坦到中国的政治敏感地区，围绕亚洲海岸的大型大三角洲。这些环境不仅受到更多人口、基础设施和生计受到威胁的影响，还受到大量人口给自然和生态支持系统带来的人为压力的影响。在孟加拉国和印度的西孟加拉邦，恒河-布拉马普特拉河-梅克纳河三角洲（GBMD）可能是世界上最大、人口最密集的三角洲系统的典型例子，在路易斯安那州大小的地区容纳了1.5亿人口。在这个沿海see项目中，一群具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及其人口的命运和未来可持续性的问题。具体来说，到2100年，三角洲是否有足够的河流沉积物来跟上海平面上升的步伐？三角洲的河流和潮汐通道网络如何有效地在整个地区分配水和沉积物？人类活动是如何影响这个渠道-网络系统的？对人类基础设施的后续影响是什么？为回答这些问题而开发的基于研究的知识如何帮助规划和决策可持续的GBMD和其他三角洲？为了解决这些问题，该项目将创新的定量工具（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，分析了GBMD的人-自然耦合系统和长期可持续性。具体而言，小组成员将(i)为整个三角洲的沉积物扩散制定详细的质量平衡；（ii）定量分析分散这些沉积物的三角洲系统网络的连通性；（iii）通过本地到全球尺度的数值模拟整合这些知识；（iv）利用景观和河道动态的观测数据来了解陆-海耦合相互作用；评价区域土壤和水资源的质量及其与自然和人为过程的联系；（六）评估这些三角洲动态对人类环境和交通的影响，最后（七）通过各种教育活动和机会向学生、研究人员和专业人员传播这些知识。小组成员与孟加拉国当地实体和大学进行了广泛合作；通过这些联系，本项目开发的知识将传播到相关的利益相关者社区。研究结果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工作尤为迫切。最终成果将提供一个有根据的、综合的、多学科的视角，来研究世界上最大的三角洲是如何运作的，以及它对下个世纪环境变化的合理反应。本项目的一些国际活动部分由国际信息组织全球风险基金的一笔小额捐款提供支助。

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.