Study of Nature-Based Solutions for the Huang River Watershed

In response to the increasingly complex challenges faced by our environment and society, there's a paradigm shift in flood management practices within the field of hydraulic engineering. Traditional approaches using gray infrastructure are giving way to Nature-based Solutions (NbS), which prioritize sustainability and ecosystem-based approaches. Despite widespread discussions about NbS potential, there's a lack of a clear framework for its application and evaluation. This paper aims to apply Nature-based Solutions (NbS) measures for the Huang River Watershed, located in northern Taiwan. A clear process for planning and assessing the benefits of NbS is established while providing relevant case studies as demonstrations. The planning process thoroughly considers the opinions of stakeholders. To evaluate the effectiveness of the implemented measures, several methods such as hydraulic modeling using HEC-RAS 2D, ecosystem service assessment via Integrate Valuation of Ecosystem Services and Tradeoffs (InVEST), and flood risk analysis through reliability analysis are adopted. Results shown that the designed wetland can reduce the flooded area downstream of the Huang River by 9.86% for a 50-year flood and by 3.95% for a 2-year flood; the designed wetland will increase carbon storage by 75.74% and reduce soil erosion by 50.77%, while habitat quality will be maintained at a similar level and the probability of flooding reduces to 3%. By leveraging the above assessment methods, this study can bridge the gap between engineering and ecological conservation fields via demonstrating the benefits of NbS implementation. The outcomes of this research are intended to serve as a valuable reference for future studies and inform decision-making processes related to similar projects.