Barchan dunes cruising dune-size obstacles

TL;DR

This study experimentally examines how subaqueous barchan dunes interact with dune-sized obstacles, revealing conditions for passage, blocking, or splitting, and proposing a classification based on key parameters.

Contribution

It introduces a classification map predicting barchan behavior near large obstacles based on experimental data and dimensionless parameters.

Findings

Barchans can pass, be blocked, or split by obstacles.

Behavior depends on two key dimensionless parameters.

Results aid understanding of dune dynamics around large structures.

Abstract

We investigate the behavior of subaqueous barchans reaching dune-size obstacles by carrying out experiments where we varied the obstacle shape and size, the flow strength, and the grains' properties. We found that a subaqueous barchan can pass over or bypass a dune-size obstacle, or even be blocked, with some intermediate situations. In the bypass cases, the original barchan can split in two or more bedforms, redistributing sand in space. Finally, we propose a classification map in which the barchan behavior depends basically on two dimensionless parameters. Our results represent a step toward understanding how barchans behave in the presence of large obstacles, such as retaining walls, tubes and bridge pillars.