Equivalent roughness of gravel-bed rivers

The relation between the equivalent roughness and different grain size percentiles of the sediment in gravel-bed rivers was determined under the hypothesis that the vertical distribution of the flow velocity follows a logarithmic law. A set of 954 data points was selected from rivers with gravel size sediment or larger, with a non-sinuous alignment and free of vegetation or obstacles. According to the results, the ks roughness is equivalent to approximately 2.4D90, 2.8D84, and 6.1D50. No correlation was detected between the sediment sorting and the sediment mobility index on one hand, and, on the other, the coefficient of proportionality of each grain size percentile.

Aportació al coneixement de l'evolució geològica recent de la plana del Ter (Baix Empordà)

The infilling of the river Ter Plain was produced by alluvial systems under the control of sea-level changes during the Quaternary. This paper describes the sedimentary evolution of the plain, and attemps to present a chronology of the recent geological events based on eustatic curves