In urban areas, the impact of flooding is significantly greater compared to rural environments, as the chance of property damage and loss of life is higher. Therefore, there is a great need for hydraulic models, which can predict flooding direction when these natural disasters occur. Structural elements (e.g. buildings, walls) represent obstacles in the flow, which considerably affect the course of the water flow and should be taken into account in the hydraulic models. In this thesis, we compared two different ways to take account of the structural elements in 2D hydraulic mathematical models. The first approach models buildings with a high hydraulic roughness coefficient for building footprints, while the second approach includes buildings in a digital terrain model at their locations. A 2D hydraulic model of the river and a city was made. There is a floodwall protecting the city and the scenario assumes that a part of the concrete wall collapses and the water spills into the city. The case study was made using HEC-RAS 5.0., which uses highresolution topographic data to develop explicit parameterization of sub-grid-scale topography. A sensitivity analysis was made as it is important to determine the effect of the cell size of the numerical mesh. The impact of cell size and the approach of modelling obstacles was checked by indicators, such as water depth, velocity of the water current, extent of flooded areas, etc. The impact of these parameters was also checked by comparing the duration of flood propagation along the urban area.
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