Tides and currents for safe kayaking near harbours

Why harbour waters reward extra care

Ask any sea kayaker who has paddled out of a busy harbour on a spring tide and you will hear the same story: the water inside the walls can look benign while the entrance is genuinely hostile. Harbours sit at the point where the open sea meets a narrow dredged channel, and that geometry does interesting things to moving water. Around much of the UK we have some of the largest tidal ranges in the world — well over ten metres on a big spring tide in the Bristol Channel and the approaches to Liverpool — and an enormous volume of water has to shift in and out through a remarkably small gap. The result is compressed, fast flow, often running at two or three knots and considerably more where training walls or a narrow entrance pinch it further.

Add wind, ocean swell and the wash of commercial traffic, and you have a situation that deserves a proper plan rather than a hopeful glance at the sky.

Reading the tidal stream before you launch

Start with the chart. Tidal diamonds give you the direction and rate of the stream at specific positions, usually quoted for springs and neaps at high water, and the almanac tells you how to interpolate for the hour you actually plan to be there. Remember that slack water rarely coincides with high or low water; in estuaries and long channels it can lag by well over an hour, and the stream may still be flooding after the tide has begun to fall.

• Identify the standard port for your area, then apply the corrections for a secondary port if your launch is some distance away.
• Check whether it is springs or neaps. The difference in flow rate can be nearly double, and a comfortable paddle on a neap can become a real fight on a spring.
• Note any local oddities — double high waters, eddies behind breakwaters, and back eddies along harbour walls where you can tuck in out of the main stream.
• Use the rule of twelfths for depth over a sill or a shallow slipway: one twelfth of the range in the first hour, three twelfths by the second, six by the third, and so on.

Local knowledge is worth more than any table. A friendly word with a harbour office, a sailing club or a resident kayak group will often tell you exactly where the stream runs hardest and where it is safe to wait it out.

Wind against tide: the classic small-craft trap

When wind blows against the direction of the tidal stream, the sea state escalates quickly. Short, steep waves stand up in water that was flat twenty minutes earlier, and overfalls develop off headlands, harbour mouths and sandbars. Our prevailing south-westerlies mean that an ebbing tide through a west-facing harbour entrance is often the worst combination, particularly on springs.

Wind over tide is not automatically a reason to stay ashore, but it should change your route. Ask yourself:

• Can I paddle with the stream rather than against it on the exposed leg?
• Is there a sheltered alternative inside the harbour or behind a breakwater?
• Have I left enough time and energy to abort and return before the worst of it?
• Would a shorter day, or a launch from a different slipway, solve the problem entirely?

Be honest about your group's ability. A choppy harbour entrance is a serious place to discover that a paddler is not comfortable in clapotis.

Shipping channels, ferries and blind corners

Harbours are workplaces. Ferries, fishing boats, tugs and commercial craft are constrained by draft and by timetable, and they will not be able to stop for you. Keep well clear of the main channel wherever there is room, and when you must cross it, do so at right angles and briskly, in a tight group rather than strung out.

Carry a VHF radio — a handheld is fine — and keep a listening watch on the harbour's working channel and on the distress and calling channel. A short, clear call to port control or a ferry skipper to confirm your intentions is never wasted, though never assume a call gives you right of way. Be aware that kayaks show up poorly on radar and may not be seen at all behind a swell or a harbour wall. Treat every blind corner as if something large is coming.

Kit and habits that earn their place

Beyond the usual buoyancy aid and appropriate immersion clothing, two items stand out for harbour paddling. The first is that VHF radio, which turns a worrying situation into a brief conversation and lets you hear what the big vessels are planning. The second is a towline, kept accessible rather than buried under the deck. Tired paddlers, a swamped cockpit or a paddler who cannot make headway against the stream are all solved far more easily with a tow than with brute effort.

• A towline with a quick-release harness and enough float to keep clear of the water.
• A spare paddle, splits are ideal, and a paddle float if you paddle alone.
• A personal locator beacon and a waterproofed phone as a backup to the radio, not a replacement.
• A chart or printed tidal plan in a deck bag, plus a note of the day's high and low water times.

Planning the launch and the return

Work backwards from the tide rather than forwards from your alarm clock. Decide when you want to be back inside the harbour, add a margin, and build the day around that. Aim to be off the water before the stream builds against the wind, and have a plan B landing in mind if the entrance has other ideas.

Leave a float plan with someone ashore, noting your route, your estimated return and the number in your group. Check the weather forecast the night before and again on the morning, and look at the actual sea state from the slipway before committing. Harbours are wonderful places to launch from — full of history, working boats and sheltered water — and a little time spent with the tide tables is what keeps them that way.