Mosul dam is one of the biggest hydraulic structures in Iraq. It is located on Tigris River north Iraq and was selected as a case study to predict flood disasters caused by a hypothetical Mosul dam failure due to its foundation defect in which the dam had been survive since 1986 (initial time of dam operation). It is an earth-fill zoned dam with 105 meter height and 11.1 billion cubic meter of volume capacity. The objectives of the present research were to predict the characteristics of the flood wave due to a hypothetical Mosul dam break and to estimate damaged areas downstream, specially in Mosul city (the second largest city in Iraq), applying the simplified dam break model (SMPDBK) and utilizing the geographic information system.