Flood Forecasting for the Greater Zabb Tributary of Tigris River Using the Probability Techniques

The climate change in Iraq from 1933 until 1992 that caused fluctuation of rainfall led to fluctuation of rivers discharge. The increasing of rainfall intensity may cause flood which will impact on human by flooding the neighboring town that lead to damage the houses and human loss; while the decreasing of rainfall causes the scarcity. Therefore accurate forecasting must be done to measure the maximum incomes of discharge by statically analysis in rivers through 56 years to predict the maximum discharge through recurrence interval (T) 10 ,25 ,50 ,100 ,200 ,1000 ,10000, and 105years. In this study the data of Greater Zabb river in Aski Kelek station will be used because of it is not controlled by dams. In this research analyzing river flood is done by utilizing of Gamble, Log person type III., Normal distribution, Log normal distribution, Weibull distribution and GEV(General extreme value) that used by PWM (Power weighted method) distribution. The obtained results of this research were close in all used methods of T = 1000 year except the log normal distribution and GEV, whereas they were higher than the other distributions. Moreover; the outcomes of previous study for suggested dam (Bakhma dams) on the river which are Japanese report 1979, the study of Swiss consultants 1985, study and water resource design 2005 were close to t the outcomes of this research. The many distributions give a lot of probabilities of flood to obtain a clear view of maximum inflow (flood) to river and best design of reservoir.