AbstractA hydrologic model for urban areas has been developed which incorporates distributed parameter modelling concepts and functions in the context of a geographic information system. In the proposed model, the watershed is represented as a cascade of grid cells, whose size can be specified by the user. Preliminary processing includes the determination of overland flow directions for each cell. An automated procedure is used to establish the cell‐to‐cell connectivity scheme, which is used to order the computations within each time step. Infiltration is computed using the Green‐Ampt equation, while runoff rates are computed using a coupling of the continuity equation and Manning's equation for turbulent flow. Storm sewer flows are routed using time‐shift routing. The model is capable of simulating flow through streets and offers the possibility of predicting the downstream movement of sewer system overflows. In preliminary testing on a small residential watershed, the model was able to reproduce measured hydr