Kmait River is a flood escape that was constructed to divert water duringflood season from Tigris River to Al Huwayza Marsh through AsSanna'f Marsh.Water stored in Al Huwayza Marsh is then discharged to Tigris River, through AlKassara River, and to Shatt Al Arab River, through AsSuwayb River.Kmait River, AsSanna'f Marsh, and Al Huwayza Marsh form onehydrological system. Therefore, the capacity of AsSanna'f Marsh and the capacityand operation schedule of Al Huwayza Marsh were taken into consideration whendeveloping the capacity of Kmait River.It was found, by using a one dimensional flow simulation model, that thepresent discharge capacity of Kmait flood escape does not exceed 80m3/sec, andthis discharge can’t be diverted completely into Al Huwayza Marsh during Januaryand February months of a wet year unless the discharge capacity of AsSanna'fMarsh outlet is increased from its current capacity of 402m3/sec to 468m3/sec.It was found that the contraction in last part of Kmait River is throttling thedischarge. If this part is reshaped, the capacity of Kmait river will increased to250m3/sec, which could be diverted into Al Huwayza Marsh if AsSanna'f Marshoutlet reshaped and its capacity increased to 569m3/sec.Depending on the maximum allowable monthly inflow of Al HuwayzaMarsh incase of replacing its present outlets control structures by new ones with acapacity of 500m3/sec, Al Huwayza Marsh will absorb floods diverted from TigrisRiver at design capacity of the control structure of Kmait River of 400m3/sec afterreshaping the river cross sections and increasing the discharge capacity ofAsSanna'f Marsh outlet to 744m3/sec.