Manning’s Roughness Coefficient

08/19/25

“How can we measure the resistance to fluid flow in channels and floodplains?”

Fluids flow through open channels in conduits and floodplains. The structures supporting fluid flow provide resistance to movement. The structure’s base surface roughness, stage and discharge, obstructions, geometric irregularities and alignment, vegetation, and debris contribute to fluid resistance. These are quantitatively summarized by Manning’s Roughness Coefficient, a variable vital for channel flow calculations. Manning’s roughness coefficients for various materials are found in engineering reference manuals.