Rising sea and sinking land: Determining spatially resolved subsidence rates for the Ayeyarwady Delta (Myanmar) and developing dynamic adaptation scenarios for the increased risk of flooding

根据IPCC最新的温和预测，到2100年，全球平均海平面预计将上升0.32-1.01米。在均衡作用和压实作用超过沉积作用的地方，大型三角洲容易出现异常的海平面上升速率。在未被充分研究的伊洛瓦底三角洲（缅甸），相对SLR导致最低地区被淹没，而热带气旋引起的季风洪水和风暴潮对三角洲的大部分地区构成威胁。最近事件的灾难性影响表明，对伊洛瓦底三角洲高震级灾害的认识有限的后果，在那里，巨大的灾害风险与高水平的暴露和有限的恢复能力相适应。因此，提高对海平面、洪水和社会活动之间的因果关系的理解，作为未来减灾和风险治理战略的基础，已经成为2019年批准的初始项目的目标。尽管2019冠状病毒病和2021年2月缅甸发生的政变严重阻碍了实地工作的开展，但通过应用遥感技术，该项目在评估伊洛瓦底三角洲的洪水灾害、脆弱性和风险方面取得了重要成就。然而，为了制定针对未来洪水风险的可持续缓解战略，进一步了解相对SLR的驱动因素和有效的适应战略至关重要。这是我们后续提案的重点，该提案将首次系统地调查地面沉降对当地SLR的贡献，并针对三角洲的灾害风险减少策略。到目前为止，伊洛瓦底江三角洲的地面沉降只在当地进行了评估，它对相对SLR的贡献是基于模糊的估计，尽管它构成了自然系统和社会活动之间的关键联系。为了了解社会与减轻或可能造成的灾害风险之间的相互作用，需要有关地面沉降时空格局的数据。这些发现为风险敏感型适应战略提供了基础，这些战略将通过涉及当地和国际专家的基于情景的规划来制定，旨在共同创造知识。这将有助于制定应对战略，以便为子孙后代保护三角洲的住区和经济功能。因此，后续建议旨在通过以下方式进一步改善伊洛瓦底三角洲洪水风险的评估和缓解：(i)提供关于地面沉降作为相对SLR的主要驱动因素的新的、独特的数据；（ii）研究相对单反与人类活动之间的相互依赖关系；（三）为未来洪水风险的可持续管理开发动态适应性途径。从识别单反驱动因素到发展适应途径的整体方法可以作为一个模型，也适用于其他大三角洲。

According to the latest moderate IPCC projections, global mean sea level is expected to rise by 0.32–1.01 m until 2100. Large deltas are prone to exceptional rates of sea-level rise (SLR) where isostasy and compaction exceed sedimentation. In the understudied Ayeyarwady Delta (Myanmar), relative SLR leads to drowning of the lowest areas, while monsoon floods and storm surges induced by tropical cyclones are a threat to much larger parts of the delta. The catastrophic impacts of recent events demonstrated the consequences of limited knowledge concerning high-magnitude hazards in the Ayeyarwady Delta, where great disaster risk meets high levels of exposure and limited resilience capacity. Therefore, an improved understanding of causalities between sea levels, flooding and societal activities as the basis for future strategies of mitigation and risk governance was already targeted by the initial project granted in 2019. Although the implementation was considerably hampered by Covid-19 and the coup d'état in Myanmar in February 2021, which has been making fieldwork impossible, by applying remote sensing the granted project made important achievements regarding the assessment of flood hazard, vulnerability and risk in the Ayeyarwady Delta. However, to develop sustainable mitigation strategies for future flood risk, further insights into the driving factors of relative SLR and effective adaptation strategies are essential. This is the focus of our follow-up proposal, which for the first time will systematically investigate the contribution of land subsidence to local SLR and target disaster risk reduction strategies in the delta. As yet, land subsidence in the Ayeyarwady Delta has been assessed only locally and is contribution to relative SLR is based on vague estimates, although it constitutes a crucial link between the natural system and societal activities. Data on spatial and temporal patterns of land subsidence are needed to understand interactions between society and the mitigation or potential creation of disaster risks. These findings provide the basis for risk-sensitive adaptation strategies, which will be developed through scenario-based planning involving local and international experts, aiming at the co-creation of knowledge. This will contribute to the development of coping strategies in order to preserve settlements and economic functions of the delta for future generations. Consequently, the follow-up proposal aims to further improve the assessment and mitigation of flood risk in the Ayeyarwady Delta by (i) providing new, unique data on land subsidence as a main driver of relative SLR; (ii) investigating the interdependencies between relative SLR and human activities; and (iii) developing dynamic adaptive pathways for sustainable management of future flood risk. The holistic approach from the identification of SLR drivers to the development of adaptation pathways can serve as a model that is also applicable to other megadeltas.