During the INTERREG-project Polder2C's 24 overflow tests were executed on a grass covered levee. The manning roughness value of the grass cover was calculated based on data of equilibrium velocity as function of discharge for overflow tests on test sections B-OF8, N-OF3 and N-OF4. This dataset contains the data for the calculation of the manning roughness value of the grass cover.

For test sections B-OF8, N-OF3 and N-OF4 the manning roughness value of the grass cover layer was derived based on the relation between the calculated equilibrium velocity and the measured discharge during the overflow test. For these test sections the equilibrium velocity was calculated based on the flow velocity derived from Particle Tracking Velocimetry.