A physically based distributed hydrologic model is developed in this study for flood inundation simulation combining newly developed overland and channel network flow simulation models with evapotranspiration, unsaturated zone and saturated zone models. The overland flow and river flow models are validated individually with test data, and then coupled with other models. The model can take fine resolution spatial data as input preserving spatial heterogeneity of physical characteristics of a river basin. River embankments play an important role in flood prevention. The model can incorporate river embankment data in flood inundation simulation. The model is applied in a river catchment in Japan to simulate a flood event in 1996. Outputs from the model show good agreements with observed flood hydrographs and surveyed flood inundation. Copyright © 2000 John Wiley & Sons, Ltd.