The patterns left by the retreating tide on sandy beaches are among my favourite photographic subjects.

Many of the beaches on the west coast of Scotland feature white shell sand as well as darker mineral-based material. On some islands, such as Mull, darker volcanic sand is also present.

The patterns typically fall into two categories – ‘bars’ left by repeated wave action, and those caused by dendritic drainage, with the characteristic ‘tree’ shapes that this produces.