Hurricane Ida in New York Fact Sheet 3: Understanding Stormwater Runoff in Highly Urbanized Areas

This FEMA fact sheet explains how stormwater runoff behaves in highly urbanized areas, with a focus on New York City. It details the relationship between impervious surfaces, surface runoff, and the capacity of urban stormwater drainage and combined sewer systems. The document highlights the impacts of intense storms, such as Hurricane Ida, on urban flooding, building damage, and infrastructure failures, and outlines regulatory and design considerations for stormwater management. It is intended to inform building professionals, community officials, and the public about urban flood risks and mitigation strategies.