Determination of Form Friction Factor

Friction factor plays a fundamental role in hydraulic analysis and design. In coarse-bed rivers friction factor depends on grain size and bed forms. Considering boundary-layer characteristics, this study first determines the total friction factor in gravel-bed rivers with bed forms. Then it determines the grain friction factor by the Keulegan and the Shields parameter methods and compares these methods. Finally it determines the form friction factor by subtracting the grain friction factor from the total friction factor. Field observations are employed to test the methods.