Protecting heritage: Insights into effective flood management using green infrastructure in a highly urbanized environment

Developing flood resilience in heritage cities is an exigent challenge of rapidly urbanizing cities of the Global South. While Green Infrastructure (GI) intervention is generally considered an important flood adaptation measure, the limited space availability combined with complex urban hydrodynamics makes the objective assessment of its efficacy challenging. Our study addresses this by integrating a 1D-2D hydrodynamic model with high-resolution remote sensing datasets, including satellite imageries derived from Sentinel-1 and Sentinel-2 and flood levels obtained from field surveys to generate contextualized urban flood maps that consider the constraints of heavily urbanized land areas in the city of Ahmedabad, a rapidly urbanizing historic city in western parts of India. Historically, this city has not been flood-prone, but the high intensity of urbanization is rendering the city extremely vulnerable to flooding risks. We investigate the efficacy of four individual Green Infrastructure(GI) facilities in managing urban stormwater based on contextual space and resource availability. The efficiency is quantified based on runoff reduction coefficient, flood extent, and peak flood depth metrics. The results show that permeable pavements are the most efficient, reducing flood volume and flooded area by 23% and 1.5%, respectively. However, these benefits were marginal, challenging the current understanding. Our findings underscore the necessity for location-specific GI solutions in urban flood risk management.