Analysis dam failure and flood inundation mapping: a case study of Manbaa-Al-Ghozlan dam, Biskra, Algeria

Abstract

Floods in all their form are considered a real threat to many regions of the world. There are various types of floods, including those caused by the collapse of dams, which must be predicted to mitigate their effects. One of the non-structural solutions for flood mitigation and control is drawing the dam failure hazard map using effective and accurate flood models, which are essential for flood disaster prevention and mitigation. The study aims at the delineation of the flood plain area caused by Manbaa-Al-Ghozlan dam failure in the city of Biskra (About 40 km downstream the dam) and the surrounding communities (the village of El Outaya). Two scenarios were considered and simulated using the HEC-RAS 2D (River Analysis System) software, the first one is related to the sudden collapse of the dam and the second linked to under-evaluations of the projected flood of the dam spillway. The results of the first scenario confirmed that there are no risks threatening the city of Biskra taking into account the water depth which reached 5 meters in the city of El Outaya. Conversely, the water depth varying between 16m and 40m in the city of El Outaya and can exceed 16 meters in the city of Biskra for the second scenario, and this performs as a great danger for the zone. This simulation allowed designing the dam failure hazards map, which showed the areas threatened by flood waves, and consequently required a plan of security measures to moderate as much as possible the consequences of a dam collapse.