Dams are constructed to provide benefits to society, hydropower generation, including water supply management and flood control. However, floods caused by failure of a dam is quite catastrophic for lives, properties and environment. Flow models for dam break scenarios ensures crucial information about land use planning and risk managment to minimize flood losses. In this study, estimation of flood innundated areas caused by flood triggered by failure of Urkmez Dam in Izmir is carried out by using HEC-RAS onedimensional (1D) unsteady flow routing model (full Saint Venant equations) and two dimensional model (2D) (full Saint Venant equations or Diffusion wave equations). The experimental distorted physical model provides controlling to simulations. The aim of the paper is to assess the risk of a dam failure potential by comparing performances of 1D and 2D simulations. Two models were compared considering the required data, data preparation, inundated area, flood velocity, flood depth, and flood waves. Keywords: Dam Break, Flood routing, Flood mapping, HEC-RAS 1D model, HECRAS 2D model