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چکیده
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The rank of floods is high among the major recurring and devastating natural perils causing global and extensive economic losses to infrastructures and most importantly human lives. Maysan city, in southern Iraq, is susceptible to recurrent floods and recently it has been affected (severely) by the Flood of 2019. Flood hazard management, therefore, is an important strategy for flood control and flood hazard reduction. The study focused on Flood Hazard Management in Tigris River, downstream of Al-Kut Barrage – the Al-Musandaq Escape, 169 km in length. This reach included one main lateral outflow, intakes, and two lateral inflows, and tributaries. Five growing islands and one sidebar were developed within the reach of the river, which represent obstacles to any anticipated flooding. This examination embraces the effect of flooding on the cross-sections of the Tigris River downstream of the Kut Barrage – the Al-Musandaq Escape, flood management, and flood control. By using the HEC-RAS model, 169 cross-sections surveyed in 2017 were employed in this study. Information related to the hydrological and topographical Digital Elevation Model (DEM) data were used as the input data. From the results of the calibration process, an excellent correlation is indicated between the simulated and observed flow data for Manning roughness coefficient, with an ‘n’ value of 0.031 for Tigris River, and 0.028 for the Al-Musandaq Escape. The Root Mean Square Error (RMSE) values were 28.474 and )Mean Absolute Error (MAE , respectively, while the values of the/s3m 10.571 Sutcliffe Efficiency -Nash nd thearespectively, /s3mand 9.0337 24.34 wereCriteria (NSE) were 0.979 and 0.986, respectively, all of which were within the good range. After running the model, the results revealed that the flood wave had not dispersed, but was only delayed by three days prior to reaching the city of Maysan and causing the flooding. Two methods were implemented to disperse and control the flood wave; the first was to remove the islands and sidebars from the Tigris River in the study area, and the second, to design a weir with an optimal level. However, removing the islands and sidebars from the river does not disperse the wave. Further, as the processes involved in dispersing and trimming the river are both difficult and expensive, this method was not implemented. Several scenarios were conducted to design a weir having an optimum level that would prevent the e city of Maysan during the flood /s flowing into th3passage of an excess of 700 m/s during the dry season, and these were 3season and no flow below 250 m. /s)3four peak flows: (4000, 2500,1050, 533, and 250 mperformed for The optimum level is the one that prevents the passage of more than 700 m3/s flow into the city of Maysan during the flood season and not less than 250 m3/s during the dry season, which is 9.4.
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