Influence of “defects” on sorted bedform dynamics

Abstract

Bedforms with plan-view patterns consisting of long crests interrupted by defects occur ubiquitously in subaqueous and subaerial environments where they strongly influence flows and sediment transport. We explore how such patterns adjust to changes in the external forcing. We utilize a numerical model of a wide-spread, large-scale seabed pattern, ‘sorted bedforms,’ examining their response to changes in wave forcing. Numerical experiments show that the pattern adjustment progresses through two stages characterized by defect propagation and defect creation, respectively, and that the rates of the initial stage, and therefore overall pattern adjustment, are determined by the initial defect density. All characteristics of the sorted bedforms are similarly influenced by the presence of defects. Although the processes of growth are likely to be different for other types of bedforms, it is reasonable to expect they will be similarly influenced by defects in pre-existing patterns.