Bedload transport and bedforms migration under sand supply limitation

Abstract

Most studies on sediment transport and bedforms migration consider unlimited sediment supply conditions. However, areas where the sediment supply is limited are common in coastal and fluvial environments. The present paper, based on physical modelling in a flume and on a re-analysis of field data obtained in the Eastern English Channel by Ferret (Morphodynamique des dunes sous-marines en contexte de plate-forme megatidale (manche orientale). approche multi-echelles spatio-temporelles, 2011), considers the effects of sediment supply limitation on bedload transport and bedforms migration velocity. The bedload transport is found to be proportional to the fraction of the bed covered by sediments for a bed exhibiting bedforms. The migration velocity of bedforms depends on the dominant mode of sediment transport. A new formulation showing a good agreement with experimental tests and observations in the field is proposed for the dimensionless migration velocity of these bedforms when sediment transport is dominated by bedload, under unlimited sediment supply conditions. For limited sediment supply conditions and sediment transport dominated by bedload, an adaptation of the formulation is suggested from flume data sets, based on the fraction of the bed covered by sediment.