Study of Geometric Elements for the Proposed Protecting Dam Reservoir in Al-Fat'ha Area, Iraq

Abstract

Partially constructed Makhul dam may collapse after the operation due to the geological and geotechnical background of the foundations zone, and the presence of gypsum layers in this zone, Then the construction of Al-Fat'ha protection dam is one of the proposed solutions. The present study used the geometric analysis method to investigate the ability of Al-Fat'ha planned protecting dam to reduce the disasters of Makhul dam break. The new methodology used to derive the geometric elements of the two dams, and analyze the relations between these elements, and then exam the behavior of Al-Fat'ha proposed dam with and without the studied collapse scenarios. Fourteen collapse scenarios suggested for Makhul dam, from the level 140 m above sea level (a.s.l), to the maximum possible flood level 152 m (a.s.l). A mathematical model was derived to predict the level achieved as a response of cumulative storage in the protecting dam reservoir when the collapse of the Makhul dam occurred. The maximum level in the protecting dam reservoir to face the worst collapse scenario is 147 m (a.s.l), when the corresponding accumulated storage in the reservoir is 3414305769 m3. The results of the geometric analysis indicate that the optimum operating level for Al-Fat'ha dam in the operating conditions without Makhul dam collapse is 118.5 m (a.s.l), which corresponds to the capacity (39243587) m3. The total flooded area between the two dams was calculated for each collapse scenario of Makhul dam; it is about 44 km2 for the worst scenario when nine villages on reservoir banks will submerge. Subsequently, the study confirmed the ability of Al-Fat'ha dam reservoir to contain the direct flood wave caused by the collapse of Makhul dam.