Studying flow resistance for emergent rigid vegetation by Provenzano's database

The estimate of flow resistance in vegetated channels is a challenging topic for managing riparian vegetation, controlling channel conveyance and flooding propensity, and designing soil bioengineering practices. In this paper, flume measurements were used to study the effect of rigid emergent vegetation on estimating flow resistance. The theoretical flow resistance equation, obtained by integrating the power flow velocity distribution, was firstly summarized. Then, this flow resistance equation was calibrated and tested by experimental runs carried in a flume with a fixed and smooth bed, where rigid cylinders were set in an aligned arrangement with different tstem concentration values (0.53‐11.62 stems dm‐2). In particular, the G function of the power velocity distribution was empirically related to the channel slope and the flow Froude number for the arrangements with different stem concentrations. This calibration was carried out both by using all the available data together or using different scale factors representing the effect of the stem concentration. The analysis demonstrated that the theoretical flow resistance equation coupled with the empirical relationship for estimating the G function allows an accurate estimate of the Darcy‐Weisbach friction factor, characterized by errors always less than ± 10% and less than or equal to ± 5% for 96% of the investigated cases.