Diyala Governorate was recently exposed to high flood waves discharged from Hemrin Dam. Since the dam was at its full capacity during the flood period, these waves were discharged to the Diyala River. Because of the reduction in Diyala River capacity to 750m3/s, the cities and villages on both sides of the river banks were inundated. Thus, the study's objective is to design a flood escape out of the Diyala River, to discharge the flood wave through it. The flood escape simulation was done by using HEC- RAS software. Two hundred twenty-three cross sections for the escape and 30 cross-sections of the Diyala River were used as geometric data. Depending on the geological formation that the escape passed through, two roughness coefficients of 0.035 and 0.028 were applied. An outflow downstream Hemrin Dam varies from 1100m3/s to 1800m3/s was applied as boundary condition upstream Diyala River. One dimensional hydraulic model was developed for the escape and the river, the results showed that aside weir could be constructed at the escape entrance with crest level 67m.a.m.s.l. and 800m width, followed by drop structure of four rectangular steps, this case provides safe discharge to Diyala River if flood wave of 1500m3/s released from Hemrin Dam.
