Nikuradse Roughness Height Derived from a Physically Based Model Applied to a River Channel with Dunes

DIAZ LOZADA, JOSE M.; PEDOCCHI, FRANCISCO; GARCÍA, CARLOS M.; LIGORRIA, ANA. I HEREDIA; MARTINO, ROMAN

JOURNAL OF HYDRAULIC ENGINEERING

ASCE-AMER SOC CIVIL ENGINEERS

Año: 2024 vol. 150

0733-9429

The Nikuradse roughness height for a river channel or, equivalently, the friction factor (f) or Manning’s coefficient, are parameters required to calibrate hydrodynamic models used for flood risk management. In general, modeling hydraulic roughness includes the contributions of skin friction, related to sediment grain size, and bed-form roughness, related to bed-form geometry. Frequently, bed-form resistance is larger than the resistance due to skin friction. An empirical approach has been presented in the literature to estimating bed-form roughness, which is widely used for engineering purposes. This contribution presents an alternative physically based formulation for dune roughness estimation. Flow resistance generated by the bed form is assumed to arise from the drag force exerted by the bed, based on depthaveraged flow quantities. The new formulation agrees with existing experimental laboratory results and new field data from the Tercero (Ctalamochita) River, C´ ordoba, Argentina