Reply to Comment by J. Qin and T. Wu on "Analysis of Flow Resistance Equations in Gravel Bed Rivers With Intermittent Regimes: Calabrian fiumare Data Set"

The Authors thank the Discussers for their interest in this article and for providing further opportunity to the Authors to clarify two fundamental aspects that in the last decades have significantly affected the development of the research concerning the role of the Froude number in the flow resistance estimation in gravel bed rivers and how the same number should be used within flow resistance equations. To that end, it is useful to remember the following main purposes of the paper of Mendicino and Colosimo (2019, https://doi.org/10.1029/2019WR024819): (1) providing the scientific community with a considerable new data set of field measurements carried out in 3 years on 136 reaches of 78 gravel bed rivers in southern Italy, covering a wide range of geometric, granulometric, hydraulic, and sediment parameters; (2) pointing out that the conventional flow resistance equations considered, when evaluated in their original form, were found to be reliable only for small-scale roughness and absence of bedload transport; on the other hand, the same equations have to be used with extreme caution, both in the intermediate- and the large-scale roughness domains and, especially, when river reaches characterized by very high values of bedload transport are analyzed; and (3) investigating the benefits produced by the Froude number and a particular form of the Shields sediment mobility parameter on the flow resistance estimation, suggesting corrective terms to add to the conventional flow resistance equations considered.