Understanding Tide Tables for Coastal Walks

Why Tide Tables Should Shape Your Route

A tide table is not a formality to glance at on the way out of the door. On much of the British coast it is the document that decides whether a walk is a lovely afternoon or a soaking — or worse. Close to ten metres of water moves in and out of the Bristol Channel between high and low water, and even on gentler stretches a metre or two is plenty to turn a dry causeway into a waist-deep crossing. If your route touches a beach, a rocky platform, a sandbar, a tidal island or the base of a cliff, the tide belongs in your planning alongside the weather.

Reading the Numbers Properly

Tide tables for your stretch of coast list two things for each day: the time of high and low water, and the height of the tide at those times. The times matter most for planning; the heights tell you how much room you have.

Resist the temptation to treat low water as a single moment. What you actually want is the window either side of it — the hours when a causeway, a sandbar or a low-tide crossing is genuinely passable. A route that is ankle-deep at low water may be thigh-deep an hour and a half later, and that gap closes quickly on a big tide.

• Find the nearest standard port in the tables and check whether your beach is listed as a secondary location, with its own time and height differences.
• Work out the window in both directions — the time you need to be across, not just the time you need to set off.
• Note the height at low water. A low water of 0.3 m exposes a great deal of sand; a low water of 3.0 m may barely change the scene at all.
• Remember that heights are measured from a low reference level, not from the beach you are standing on, so the figure is a comparison rather than a depth.

Springs, Neaps and Moving Goalposts

Tides are not uniform. Around each new moon and full moon the range grows and you get spring tides; roughly a week later the range shrinks into neap tides. A crossing that is comfortable at neaps can be impassable at springs, so it is worth knowing which you are in before you commit. Add to that the fact that high water arrives roughly fifty minutes later each day, so last weekend's successful timing is not this weekend's.

When the Tables Aren't the Whole Story

A tide table describes an average, astronomically driven tide. The sea itself has other ideas, and this is where experienced coastal walkers earn their reputation.

• Weather and pressure. A deep low pressure system can lift water levels well above the predicted height, and a strong onshore wind piles water up against the coast.
• Swell. Even on a small tide, a long swell running onto a beach pushes waves further up the sand. The water may be where the table says, but the wash is not.
• Local currents. Tidal streams around headlands, estuary mouths and narrow channels can run faster than most people can swim, and they turn at their own pace.
• Rain and rivers. After heavy rain, estuaries and river mouths run higher and muddier than the tables suggest.

Wind against tide creates a short, steep chop that makes rocky platforms slippery and slipway launches awkward. If the forecast is marginal, treat the tide window as shorter than the table says, never longer.

Building the Walk Around the Water

Once you know your window, plan the day backwards from it.

• Where you can, cross on a falling tide. If something goes wrong, you have time on your side rather than water rising behind you.
• Identify your escape routes before you need them: a path up the cliff, a slipway, a set of steps, a field gate above the beach.
• Mark the point of no return in your head — the spot where turning back is still easy.
• Carry a paper copy or an offline screenshot. Phone signal vanishes in coves and beneath cliffs far more often than people expect.
• If you are paddling, sailing or launching a dinghy from a slipway, the same window applies — and the slipway may be unusable for hours either side of low water.

Tell Someone, and Stay Contactable

This is the habit that saves lives. Before you leave, tell a friend or family member your route, your expected return time, and where you have parked. Agree that they will raise the alarm if you have not checked in.

Carry a charged phone, and consider a small battery pack in a dry bag. Cliffs, coves and remote stretches of coast block signal, so do not rely on being able to call from the water's edge. In an emergency in the UK, dial 999 and ask for the coastguard. If the tide is already cutting you off, move to the highest safe ground you can reach and stay put rather than attempting a swim.

Finally, give yourself a margin. A tide table is a prediction, and the sea is under no obligation to follow it precisely. Plan to be clear of the water half an hour earlier than you think you need to be, and you will enjoy the walk far more.