[Viet Nam] Valuing the benefits of blue/green infrastructure for flood resilience, natural capital and urban development in Viet Nam

洪水是最具破坏性和最昂贵的水文气象灾害，每年影响全球数百万人。在越南，由于城市快速发展和气候变化，低洼沿海城市，特别是河流三角洲地区的城市，面临着越来越大的洪水风险和脆弱性。为了减少城市地区的洪水风险，近十年来，人们越来越重视蓝/绿色基础设施（BGI）的潜力，如自然和人工湿地、植被河岸和恢复的洪泛平原，以减少洪水风险并提供额外的好处，如控制水污染物、提供娱乐机会、改善空气质量和增强对其他压力源（如热浪和噪音污染）的抵御能力。然而，尽管在洪水风险管理方面对华大基因的兴趣越来越大，但过去对这些措施的有效性和可行性的评估大多是零散的，主要集中在这些措施的个别影响上（例如，减少洪水风险，提供城市绿地）。这种部门评估无法解释单个装置的多重影响之间的潜在权衡或互补性，更不用说整个华大基因网络了。因此，华大基因寻求开发一个多学科、利益相关者知情的评估框架，以评估华大基因在降低洪水风险和改善城市自然资本方面的有效性。因此，该项目考察了华大基因在短期和长期城市发展中的作用，并以越南芹苴市为例。这个整体框架整合了许多学科，不仅遵循相互关联的多学科研究议程，而且还推进了所涉及的各个学科的学术水平。这包括让主要利益攸关方参与研究进程，共同制定解决方案并向主要决策者传播证据；创新的城市尺度洪水和BGI高分辨率模型；对生态系统服务提供的变化进行空间明确的评估和评价，从而量化华大基因对城市自然资本的投资。为了实现这些目标，该项目包括四个工作包，它们在多学科评估框架内作为相互关联的组成部分发挥作用：(1)瓦尔华大基因的业务骨干是一个工作包，它建立了一个利益相关者小组，从头到尾与研究团队一起工作。该部分评估（并在必要时激励）地方和区域城市规划者以及其他关键利益相关者对基于自然过程的BGI替代方案的认识。(2)第二个工作包回顾了芹苴和越南湄公河三角洲的现有洪水模型，并开发了一个新的高分辨率模型系统，以评估选定的华大基因措施在降低洪水风险方面的有效性。(3)在第三个工作包中，将评估和绘制安装华大基因措施后生态系统服务提供的变化。(4)在第四个工作包中，通过评估方法量化了华大基因措施（降低洪水风险和改善城市自然资本方面）的成本和效益，并对华大基因方案进行了成本效益分析。利益相关者在华大基因的持续参与确保了决策者对研究成果的认识和吸收，以最大限度地发挥所产生的证据的影响。此外，整体方法可以更好地理解减少洪水风险与改善华大基因产生的自然资本之间的潜在权衡和互补关系。探索华大基因的所有同时影响，有助于为环境管理者和城市规划者提供支持规划决策的完整信息。

Flooding is the most damaging and costly hydrometeorological hazard affecting millions of people globally every year. In Viet Nam, low-lying coastal cities, particularly in river deltas, face increased flood risk and vulnerability due to rapid urban development and climate change. To reduce flood risk in urban areas, the recent decade has seen increased appreciation of the potential of Blue/Green Infrastructure (BGI), such as natural and man-made wetlands, vegetated river banks and restored floodplains, to reduce flood risk and provide additional benefits, such as controlling water pollutants, providing recreational opportunities, improving air quality and increasing resilience to other stressors, such as heat waves and noise pollution. However, despite the growing interest in BGI in a flood risk management context, assessments of the effectiveness and viability of such measures have in the past been mostly piecemeal, focusing on individual impacts of such measures (e.g. flood risk reduction, provision of urban green space). Such sectorial assessments cannot account for the potential trade-offs or complementarities between the multiple impacts of individual installations, let alone whole networks of BGI. Therefore, ValBGI seeks to develop a multidisciplinary, stakeholder-informed assessment framework for the effectiveness of BGI to reduce flood risk and improve urban natural capital. Thereby, the project examines the role of BGI in short- and long-term urban development, with application to the city of Can Tho, Viet Nam. This holistic framework integrates a number of disciplines and does not only follow an interlinked and multidisciplinary research agenda but also advances the academic state-of-the-art in the individual disciplines involved. This includes the engagement of key stakeholders in the research process to co-develop solutions and disseminate evidence to key decision-makers; innovative high-resolution modelling of flooding and BGI at the city-scale; and spatially explicit assessment and valuation of changes in the provision of ecosystem services enabling the quantification of the investment into urban natural capital effectuated by BGI. To achieve these objectives, the project comprises four work packages which function as interlinked components within the multidisciplinary assessment framework: (1) The operational backbone of ValBGI is a work package that establishes a stakeholder group to work alongside the research team from start to end. This component assesses (and when necessary stimulates) the awareness of alternative natural processes-based BGI options among local and regional urban planners and other key stakeholders. (2) A second work package reviews existing flood models for Can Tho and the Vietnamese Mekong Delta and develops a new high-resolution modelling system to assess the effectiveness of selected BGI measures in reducing flood risk. (3) In the third work package, changes in the provision of ecosystem services following the installation of BGI measures will be assessed and mapped. (4) In the fourth work package costs and benefits of BGI measures (in terms of flood risk reductions and improvements of urban natural capital) are quantified by means of valuation, and cost-benefit analyses of BGI scenarios are conducted. The continuous stakeholder engagement in ValBGI ensures awareness for and uptake of the research outcomes by decision-makers to maximise impact of the evidence produced. Furthermore, the holistic approach provides a better understanding of the potential trade-offs and complementarities between flood risk reduction and improvement of natural capital generated by BGI. Exploring all simultaneous impacts of BGI is beneficial in providing environmental managers and urban planners with a complete array of information for supporting planning decisions.