Resistance Coefficients for Artificial and Natural Coarse-Bed Channels: Alternative Approach for Large-Scale Roughness

Traditional Manning-Strickler and Keulegan formulas underestimate open channel flow resistance in the presence of large-scale roughness. How to theoretically evaluate resistance coefficients for large-scale roughness remains challenging in spite of significant efforts made in recent decades. The research reported in this paper provides an alternative understanding of energy losses associated with large-scale roughness. This yields a new resistance formula, of which two empirical coefficients were calibrated with laboratory and field data available in the literature. The results show that the new formula applies for both shallow and deep flows, and also agrees well with the best of previously proposed formulas.