Menai Strait - Tidal Effects

Tidal Effects

The tidal effects observed along the banks of the strait can also be confusing. A rising tide approaches from the south-west, causing the water in the strait to flow north-eastwards as the level rises. The tide also flows around Anglesey until, after a few hours, it starts to flow into the strait in a south-westerly direction from Beaumaris. By the time this happens the tidal flow from the Caernarfon end is weakening and the tide continues to rise in height but the direction of tidal flow is reversed. A similar sequence is seen in reverse on a falling tide. This means that slack water between the bridges tends to occur approximately one hour before high tide or low tide.

Theoretically it is possible to ford the strait in the Swellies at low water, spring tides when the depth may fall to less than 0.5 metres (1.6 ft). However, at these times a strong current of around 9 kilometres per hour (5.6 mph) is running, making the passage extremely difficult. Elsewhere in the strait the minimum depth is never less than 2 metres (6.6 ft) until the great sand flats at Lavan sands are reached beyond Bangor.