Localised sediment transport and submarine erosion in Tremadoc Bay, northern Wales

A detailed echo-sounding survey of Tremadoc Bay, northern Wales, shows sand waves occurring in the southeastern corner of the Bay. These are markedly asymmetrical and indicate mass water and sediment movement through a localised “deep” at the landward end of Sarn Badrig, a shoal extending some 10.5 miles southwestwards into Cardigan Bay. It is suggested that the Sarn forms an effective barrier to water movement over the greater part of its length, causing water to “pond up” in the eastern part of Tremadoc Bay under the influence of westerly winds. This water escapes southwards through the inshore channel and in doing so may actively erode the sea floor.