This paper introduces a disaster mitigation land use plan designed as a response to urban floods. Contemporary sustainable urban discussion should unleash the dualistic opposition of urbanity and nature, and confront their differences. The new urban context stimulates challenges in new thinking regarding spatial planning. Complex flood issues between ecological and compact cities make it necessary to discuss a dialectical perspective in spatial plans for channels and dykes. This study adopts Tainan City in Taiwan as a case study area and investigates the spatial distribution features of urban flood and vulnerable land use types. First, the FLO-2D model is used to simulate four urban flood situations to analyze flood tendency and land use under different scenarios. Second, spatial analysis is used to explore the spatial features of floods. Furthermore, environmental risks of urban flood are appraised to schematically represent environmental risk land use area under various flood scenarios. Finally, the preliminary future mitigation land use plan is grounded on analysis of the comparative intensity of environmental risk land use in urban flood areas.