An integrated system to improve urban hydrologic modeling with GIS, remote sensing (RS), and hydrologic simulation is presented. Satellite images for a highly developed urban area were used to automatically acquire land use information. Next, GIS derived the distributed hydrologic parameters from processed satellite images, incorporated with a GIS spatial database. GIS organized the input files for a distributed hydrologic simulation. The paper demonstrates the characteristics of an RS- and GIS-based urban hydrologic simulation. Techniques to model urban drainage with a large database are discussed. A user-friendly interface was developed for supporting design and management.