Flash flood in urban area strikes mainly the road network. In fact, the streets during flood act as streams or overland flow paths. This jam the traffic, stop the public services and interrupt the economic activities. The previous studies used to deal with urban flood as it happens in a rural area. This study presents a new approach that deal with road network as stream flow path. The new approach utilizes 3D city model to generate a modified Digital Elevation Model (DEM) which will be the base for hydrology analysis. This procedure considers the building and streets as part of topography which results the water flows through streets as reality. The flood water depth in streets is calculated and used as a risk factor. Remote sensing (RS) and Geographic Information System (GIS) techniques are used for obtaining and preparing input data to the hydraulic model. Different flood scenarios for various return periods were investigated and the flood risk code maps for road network were generated. The results obtained show that 41.2% of road network in the study area is subjected to major flood risk from fairly frequent rainfall events, this percentage reaches 80% to 90% for low frequent flood events (50 year and 100 year flooding). The new approach has been assessed through the comparison of the derived results to the actual flood data and its accuracy reached 77%. The results of this study may help the decision makers to take the necessary actions to protect people and properties.