Resistance to flow determines several hydraulic parameters in streams and rivers that should be properly represented for estimating water discharges and sediments transport. In this research, a combination between experimental and numerical models study were carried out to investigate the influence of bed roughness of flow characteristics. Seventy two (72) runs were conducted physically and verified numerically. 6 bed materials were used (Gravel, Cement, Interlock, Grass, Formica, and Vegetations). 4 discharges and 3 tail gate water levels were tested with each bed material. Results were analyzed and were graphically presented and the percentages of errors between the obtained results from the used models were reported to define the sufficient compatibility between the used models. The Manning roughness coefficient was estimated for each bed material using the experimental and numerical models. The percentages of errors between them were reported and were under estimations. The models proved that for a given bed material, the roughness coefficient was inversely proportional to the discharge and directly proportional to the tail gate water levels.