The consequence of dam failure is one of the major hazard to human life as well as to infrastructure. Huge flood waves produced by a failure of dam may have enough capability to destruct some stronger structures like power plants and industrial plants. Studies about a natural dam failure are very common, but the thesis included numerical modeling and detailed analysis of dam conditions when a dam is under abnormal flooding conditions.The old industry dam Årbogen has been failed during an intense rainfall occurred in August 2010 with three major slides along the downstream slope. The local municipality requested to Norwegian Geotechnical Institute (NGI) to carry out some immediate temporary measures and a detailed analysis of dam condition.The primary objective of the thesis is analyzing the seepage and stability of the Årbogen dam for the extreme flood condition caused by the intense rainfall. In addition, soil analysis of the deposits, determination of flood path and flow accumulation, and consequence of the dam break are considered as secondary tasks. Stability and seepage has been analyzed using the popular geotechnical software called GeoSlope. A contour map is used to explain the possible flood paths which may impact the nearest community.