Discussion on “Fall velocity of natural sediment particles: a simple mathematical presentation of the fall velocity” by She et al

The fall velocity of coastal or river sediment is usually calculated by literature formulas. Many authors have highlighted that this procedure is not really suitable for evaluating the average fall velocity of the natural sediment as a whole. A direct measurement of the sediment samples is recommended. A large number of tests with different sands settling tube diameters, falling heights and sand concentrations have been investigated. Suggestions for a correct use of the settling tube are made. Measurements on 23 sands (three of them shingles), improved the Eq. (3) proposed by She et al. (2005), showing that it could be a promising formula to calculate the average fall velocity of natural sands