Comments on “Analysis of Flow Resistance Equations in Gravel-Bed Rivers With Intermittent Regimes: Calabrian Fiumare Data Set” by G. Mendicino and F. Colosimo

Abstract

Mendicino and Colosimo (2019, https://doi.org/10.1029/2019WR024819) addressed the evaluation of flow resistance in natural gravel-bed rivers and proposed several new equations to estimate resistance coefficients by adding the Froude number and the Shields sediment mobility parameter to conventional equations. The new equations were found to better reproduce flow velocity in comparison to conventional resistance equations. However, the apparent improved performance of these new equations is due to spurious correlation. Mendicino and Colosimo (2019, https://doi.org/10.1029/2019WR024819) incorrectly calculated the resistance coefficient by substituting the measured Froude number into the new equations, which should be solved iteratively. If the new equations were calculated correctly, they are no better than the original equations.