On the formation of current ripples

J Bartholdy; V B Ernstsen; B W Flemming; C Winter; A Bartholomä; A Kroon

doi:10.1038/srep11390

On the formation of current ripples

Sci Rep. 2015 Jun 12:5:11390. doi: 10.1038/srep11390.

Authors

J Bartholdy¹, V B Ernstsen¹, B W Flemming², C Winter³, A Bartholomä², A Kroon¹

Affiliations

¹ Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1305 Copenhagen, Denmark.
² Marine Science Department, Senckenberg Institute, Suedstrand 40, 26382 Wilhelmshaven, Germany.
³ MARUM, University of Bremen, Leobener Strasse, 28359 Bremen, Germany.

Abstract

For grain sizes finer than coarse sand, the first flow-transverse bedforms to develop are current ripples. Although numerous studies have analysed different aspects of bedform morphodynamics, to date no comprehensive physical explanation for the formation of ripples has been given. We offer such an explanation based on a virtual boundary layer concept, and present a model predicting ripple height on the basis of grain size, current velocity and water depth. The model contradicts the conventional view of current ripples as bedforms not scaling with flow depth. Furthermore, it confirms the dependence of ripple dimensions on grain size, and their relative insensitivity to flow strength.