HARBOURS WHAT TO EXPECT...

SHELTER FROM THE WAVES

The concept of a harbour is to provide shelter from the waves and most harbours do this most of the time – but not always. Some harbours are naturally better than others, but as a general rule they will be at their best when the wind is blowing offshore. However, if the harbour is big enough then swell can form on the leeward (downwind) side, so conditions are smoother on the windward (upwind) part of the harbour.

ROUGH WITH ONSHORE WINDS

Every harbour has an Achilles’ heel, and it is generally the onshore wind. This varies depending on the geography of the coast and the direction the harbour entrance faces, but the better harbours will be sheltered from the prevailing winds, with the onshore wind ideally being the least common direction.

DRAMATIC AT THE ENTRANCE

Even when the harbour is calm inside, it can be impossible to get in or out because the entrance is too rough. The main reasons for this are waves hitting the harbour wall and bouncing back out to sea and colliding with the oncoming swell, creating rogue waves that look like a boiling cauldron being stirred. Secondly, if the tide is ebbing, then it often generates currents flowing out to sea and when these hit the incoming wind, steep breaking waves called overfalls will form.

DRYING OUT AT LOW TIDE

Many harbours around the British Isles experience large tidal ranges with the result that they dry out at low tide. Despite making it impossible to get in and out, the advantage of drying harbours is that they protect boats from big storms because there can be no waves to cause damage.