Evolution of grain size composition of the pebbly river-bed alluvium from mountains to plains

The main signs of grain size transformation for pebbly river sediments from mountains to plains are examined with application of the detailed analysis. Under the description of grain size curves, such characteristics as subdistributions and modes are used. The sampling of sediments in many rivers of the former USSR was conducted in field expeditions. The data on grain size evolution are presented as transformation of polymodal curves into bimodal.