The purpose of this paper is to develop a new method to analyze the water environment in an urban area by modeling a “Water Path Network” using GIS Hydrology Modeling. “Water Path Network” is defined as a sequence of network-like passages of surface water with a view point of co-environmental urban planning looking at the relationship between road network and surface water flow. The method enables to classify six characters of water environment in an urban area; flood inundation, intercept of water system oweing to infrastructure, increase of water environmental load caused by reclamation, increase of water environmental load by land readjustment projects, surface water clot area, and passive water path. This new method will contribute to the realization of co-environmental urban planning by giving an urban landscape a rationally-designed water environment system.
