I have often wondered how Barmouth beach is so large and wondered at its natural beauty. Expecially the vast quantities of the beautiful sand. But I have now learned that the vast size is a relatively recent phenomenon and not so natural.
At the entrance to the Mawddach estuary, just in front of the southern most point of Barmouth town was the island of Ynys y Brawd. Ynys y Brawd was once a small island of dunes separate to Barmouth. The North Channel of the Mawddach estuary used to run between the southern end of Barmouth headland, and Ynys y Brawd. This channel was closed off and a new concrete causeway built out to the island in the early 1970s. There is now a developing dune system around the island with an extensive build up of new sand beach in front of the southern part of the town.
For more detail please see the attached pdf.
I attach a couple of historic photographs below and encourage visitors to the site to review the wonderful collection of local photographs compiled by Hugh G. Roberts.