تاثير روش هاي مختلف تعيين ضريب زبري مانينگ در برآورد وسعت اراضي سيل گير (مطالعه موردي رودخانه بابلرود)

Effect of applying different Manningʹs roughness coefficient determination methods to estimate the amount of flooding area(Case study, Babolroud River)

In order to investigate the effect of applying different methods of Manningʹs roughness coefficient determination to estimate the amount of flooding area, HEC-Geo-RAS software was applied. This software can be linked with HEC-RAS and AreView softwares. A part of a river with 5.5 km length and 103 cross sections was considered and divided into 10 reaches by field observation. In order to estimate the amount of Manningʹs coefficient tier main channels and banks of reaches, 5 different methods were applied as follows: Cowen, photos and slides, Iranian management and plan organization, soil conservation services (SCS) and Chow. Seven amounts of floods with different return periods were considered and their flooding areas were estimated by the mentioned methods. Comparison of the estimated flooding areas, by different methods revealed that some tens of thousands of square meters diversity could be achieved. Cowen and photos and slides methods had the lowest and highest estimations, respectively. Almost similar results were obtained from Cowen and SCS methods and from Chow and Iranian management and plan organization methods. The results of photos and slides method, on the other hand, were not comparable to any of the other methods.