Determination of Roughness Coefficient of chi River and Its Flood Plain

Abstract

A determination of Manning’s roughness coefficient (Manning’s n) of Chi River and its flood plain is presented, The Chi River basin model was created by using the Info Works RS soft ware, The model calibration was then carried out by varying the Manning’s n of the river, by trial and error, until the calculated discharge hydrograph coincided with the recorded discharge data, Therefore, the obtained Manning’s n was the most proper value for the river reach, The required input data for the model were including  stage and discharge hydrograph at various stations along the river. Discharge hydrograph from each sub-basin, the stream cross-sections. Ground model which was reacted from GIS data base. I he discharge hydrograph from each sub-basin was generated from the relationship between averaged annual stream flow and the watershed area of stream gauging stations in the basin. The relationship was then adjusted by a correction factor and multiplied with a discharge   hydrograph at the specified index station to achieve a daily discharge hydrograph. Besides, the Manning’s n of the flood plain was calculated and weighted corresponding to its land use. The results of this study could not only be used for flood routing in the Chi River basin but also be applied for determining the Manning’s n of other river basins.