Combining hydraulic roughness measurement results with Manning's roughness coefficient in drainage channels

To measure its reliability, the quality of work and materials should be assessed using objective tools and methods. For example, concrete quality is measured using tools and methods of compression testing or a hammer test tool; the results are expressed in terms of characteristic compressive strength (f'c). Steel quality is determined by the tensile test method, and the quality or strength is expressed in tensile strength (fy). The quality of the highway surface is determined by the roughness test method using the NAASRA roughness meter and the results are expressed with good, moderate and poor criteria, correlated with the International Roughness Index (IRI) value, namely good roughness if the IRI value is <75 inches/mile, moderate for IRI values between 70-170 inches/mile and poor IRI > 170 inches/mile. The hydraulic quality of the drainage channel surface to date cannot be determined with objective tools and methods. Similar to the quality of the road surface, the hydraulic quality of the channel is also determined based on the criteria: good, moderate/normal, and poor, correlated with the Manning roughness coefficient; the difference is that there is no objective value for the good, moderate, and poor criteria.