Strategic deployment of nature-based solutions for urban flood management in high-density urban landscapes
Mo Wang, Jiayu Zhao, Ziheng Xiong, Menghan Zhang, Lie Wang, Soon Keat Tan
Abstract
Urban floodings are frequently observed in high-density urban landscapes (HDULs). The rapid rate of urbanization, increased impervious land surface, limited permeable open areas, and climate change add to the challenges in flood management and mitigation in such areas. Constrained by limited space and increased peak stormwater runoff, the conventional grey infrastructure appeared inadequate in its drainage function and capacity, Nature-based solutions (NBS) have emerged as an attractive alternative to urban flood management while offering multifunctional benefits for flood risk reduction, ecosystem restoration, and urban resilience. A comprehensive framework integrating spatial multi-criteria evaluation (SMCE) with analytical hierarchy process (AHP), and entropy weighting (EW) methods is described herein. This framework is used to assess exposure, vulnerability, and adaptability factors influencing flood risks in Shenzhen, China. The study identifies key priority areas for NBS implementation and evaluates four NBS schemes based on their technical feasibility and spatial suitability. Results reveal that indices such as river network density (26.6 %) and impervious surface percentage (26.5 %) significantly influence exposure, while cultural heritage (31.2 %) and emergency shelters (58.0 %) dominate vulnerability and adaptability assessments, respectively. These results are presented in the form of a prioritization map and highlights critical zones requiring immediate intervention. Four schemes of NBS implementation involving green areas of various sizes (8.4–––28.5 km2), comprising certain areal expanse and distribution of pavements, porous surfaces, raingardens, retention ponds and constructed wetlands are evaluated to illustrate the opportunity, potential benefits, and versatility of such schemes in HUDLs.