HEC-RAS Model for Mannnig’s Roughness: A Case Study


Channel roughness is considered as the most sensitive parameter in development of hydraulic models for flood forecasting and flood inundation mapping. Hence, it is essential to calibrate the channel roughness coefficient (Mannnig’s n value) for various river reaches through simulation of floods. In the present study it is attempted to calibrate and validate Mannnig’s n value using HEC-RAS for Mahanadi Riverin Odisha (India). For calibration of Mannnig’s n value, the floods for the years 2001 and 2003 have been considered. The calibrated model, in terms of channel roughness, has been used to simulate the flood for year2006 inthe same river reach. The performance of the calibrated and validated HEC-RAS based model has been tested using Nash and Sutcliffe efficiency. It is concluded from the simulation study that optimum Mannnig’s n value that can be used effectively for Khairmal to Barmul reach of Mahanadi Riveris 0.029. It is also verified that the peak flood discharge and time to reach peak value computed using Mannnig’s n of 0.029 showed only an error of 5.42% as compared with the observed flood data of year 2006.

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P. Parhi, "HEC-RAS Model for Mannnig’s Roughness: A Case Study," Open Journal of Modern Hydrology, Vol. 3 No. 3, 2013, pp. 97-101. doi: 10.4236/ojmh.2013.33013.

Conflicts of Interest

The authors declare no conflicts of interest.


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