A Study of Calculation Manning Roughness Methods: The Case of a Small River in Southwestern Iran

Affected by numerous elements, the estimation of manning's roughness coefficient is of great importance and sensitivity. In the present study a reach of 56 km from beshar river in kohgiluyeh and boyer-ahmad province was studied. The selected reach was divided into 12 sub-reaches based on similar characteristics. Experimental and quasi-experimental methods, tables, and cowan's method were used to estimate manning's coefficient. The estimation results were compared with stage-discharge rating curves from two hydrometric stations located in the selected reach. The ‘inverse solution’ was proved to be the best method to estimate manning's coefficient in the river under study followed by bruschin and cowan's method with an average error of 0.237 and 0.241, respectively.