Jordan Journal of Civil Engineering

Evaluating Manning's Roughness Coefficient for Flows with Equilibrium and Non-Equilibrium Sediment Transport


Miskar Maini; Bambang Agus Kironoto; Istiarto Istiarto; Adam Pamudji Rahardjo;


One of the challenges in using the Manning equation is to correctly determine the Manning's roughness coefficient, particularly in the presence of sediment transport. The sediment transport in a river segment can be balanced (equilibrium) or imbalanced (non-equilibrium), depending on the balance of sediment entering and leaving the segment. To represent these two transport conditions in the laboratory, experiments were conducted with (SF) and without sediment feeding (NSF). One hundred eighty mean velocity profiles were measured using an Acoustic Doppler Velocimeter in both fixed and movable bed flows. The velocity profile in the movable bed flow with sediment feeding appears to be more �open� compared to the one without sediment feeding. The presence of sediment transport seems to alter the velocity profile from its logarithmic shape, particularly in the inner region, which change the Manning's roughness coefficient. The coefficient can be determined from two-point velocity measurements at z/H = 0.1 and 0.2 for both fixed bed flow with sediment feeding and movable bed flow with and without sediment feeding. On average, sediment feeding increases the coefficient by 19% compared to the non-sediment feeding case.


Manning's roughness coefficient, velocity profile, equilibrium and non-equilibrium, sediment transport, open channel flow.