The role of river channel roughness for water level modeling during the 2005 year flood on Siret river using HEC-RAS model

Résumé

At present, the value of channel roughness represents the most important parameter of hydraulic model calibration for flood mapping and flood forecasting. In practice, the roughness coefficient (Manning’s “n” value) cannot be determined from in situ surveying, but it can be automatically extracted from alternative sources, like pedological maps, ortophotomaps by digitizing each polygon associated with “n” value or using satellite images LANDSAT. For calibration of Manning’s “n” values, it was used the data from 2005, when a major flood occurred in this study area. To verify the performance of the calibrated HEC-RAS model, it was analyzed the flood peaks of observed and simulated values, and computation of root mean square error for the used hydrograph station on the lower Siret River. The study aims to present an efficient calibration method for flood mapping using HEC-RAS model.