Numerical Modeling of Flood Behavior in Roads Built in Areas with Flat Topography

Locating and height of waterways are critical factors in road designing. In mountainous areas due to the existence of sufficient slope, locating and capacity of culverts can be calculated based on the upstream watershed inflow and analytical studies for various flood return periods. While the waterway Locations and road heights in areas with flat topography are not simply possible because there are no height differences significantly on both sides of the road. In flooded times, water level behind the road begins to rise and submerges a huge area. In this case, calculating the appropriate height for road and waterways capacity to prevent overtopping is very important. Due to the nature of the flow in these areas, two-dimensional flow modeling for determination the flooding surface and water level is essential.In this paper, for case study, part of the main road Lamrd- khonj located in Fars province and near the Lamerd city is studied. Initially the flood discharge with different return period is determined by hydrological studies, then the flow behind the road is simulated with a 2D hydraulic numerical model. According to the obtained results, the dominant flow direction, possible overtopping areas, flooded surface and water level behind the road are determined. The results of model are considerably in good agreement with the traces left by the recent floods. These studies can be applied as a suitable guide for present and future roads in flat areas which are endangered by floods.