Despite the widespread implementation of flood control infrastructure, modern cities around the world remain vulnerable to flood hazards. Although flood management has in general placed less emphasis on structural measures, urban flood hazard mitigation continues to fixate on the flood control paradigm, the ideology that flooding must be prevented in the first place, as flooding is assumed to be disastrous. To promote urban flood resilience, this paper argues for the alternative flood adaptation paradigm, which concerns preventing damage when flooding occurs and allows flooding to enter the city. The argument is grounded on our fieldworks on the ecological wisdom of living with floods in the Vietnamese Mekong Delta in two hamlets, Vinh An and Ha Bao, where flooding is mostly harmless and brings benefits. To turn this ecological wisdom of the rural hamlets into practical knowledge, we extract lessons for modern cities: Modern cities need ecological knowledge to nurture ecological wisdom; and need to become agile by developing localized flood-response capacity, striving for timely systemwide adjustment, and turning amphibious. To make these lessons of the ecological wisdom actionable, we translate them into three urban design principles: Urban design should (1) anticipate and accommodate flooding, (2) incorporate the ecological process of flooding, and (3) reveal the flood dynamics to the public.