Safety around rising tides on estuaries

Why estuaries are trickier than they look

An estuary is one of the loveliest places to spend a day on the British coast, and it is also the one that catches out the most sensible people. The trouble is that estuaries look calm and shallow, and much of the time they are. Then the tide turns.

Unlike a beach, where the water usually advances in a fairly predictable line, an estuary fills from several directions at once. Water pushes in from the open sea, spreads sideways across low-lying flats, and creeps up channels that were dry an hour ago. On big spring tides in places like Morecambe Bay, the Solway Firth or the inner Bristol Channel, the leading edge of the tide can move faster than a brisk walk, and it arrives quietly, with little of the crashing drama people expect.

The result is that paths which are perfectly dry at 11am can be under a foot of cold, fast-moving water by half past twelve. People are not usually caught out by ignorance. They are caught out by a tide that came in earlier, faster or higher than they assumed.

Read the tide tables properly, not just quickly

Tide tables are your single most useful piece of kit, but they repay a careful look rather than a glance.

• Check the right port. High water at the mouth of an estuary can be an hour or more before high water several miles upstream. A table for a port twenty miles along the coast may be well out for the spot where you are standing.
• Look at the height, not just the time. A 9.4 metre spring tide and a 6.2 metre neap tide behave completely differently. On the largest tides, water reaches places it never touches on an ordinary day.
• Remember the lag. Spring tides follow the full and new moon by roughly a day or two, so the biggest tides often arrive when nobody is thinking about the moon at all.
• Know when your route is cut off, not when high water is. The path may flood two hours before the peak. That is the time that matters.

Local tide boards, harbourmaster notices and the man mending his boat on the slipway are all worth consulting. Estuary people know their water, and they are usually happy to tell you about it.

Watch the ground beneath your feet

Estuary mud is not like the mud in your garden. It is fine silt, it holds water, and it does not bear weight well. The softest ground tends to be just beside a channel, on the inside of a bend, and around the roots of eelgrass and samphire. If the surface looks smooth, glossy and slightly darker than its surroundings, treat it as suspect.

Walk with a pole if you are crossing flats, and prod ahead of you rather than testing with a foot. If you do go in, do not struggle violently; spread your weight, keep hold of the pole and edge backwards towards firmer ground. And remember that channels you stepped across on the way out, ankle deep and easy, will be knee deep or worse on the way back, because the tide fills them first and empties them last.

Causeways, fords and flooded paths

This is where the serious incidents happen. Causeways such as those leading to island chapels, tidal roads and old fords all share the same trap: the crossing is safe for a limited window, and the water arrives from behind you as well as in front.

Never cross a flooded causeway. Not in wellies, not in a four-wheel drive, not because the car in front made it. Fifteen centimetres of moving water will knock an adult off their feet, and around half a metre can float a small car. Salt water ruins engines, brakes and electrics, and a vehicle stalled in the middle of a causeway becomes a rescue job for other people.

If a causeway has a published safe crossing time, that window is usually much shorter than the full low-water period. Do not park on the causeway while you explore, and do not set off towards it "just to have a look" once the tide has turned. The sea does not negotiate.

If the water is rising around you

Turn back immediately, and aim for the shore you came from unless you can clearly see a closer, higher route. Move sideways along the estuary rather than trying to walk inland ahead of the water, which is often moving faster than you are. Do not swim a channel to save time.

Call 999 and ask for the Coastguard. Stay together, keep the phone dry, and make yourself visible: bright clothing, a torch, a whistle. Coastal rescue teams would far rather be called out for a false alarm than arrive half an hour too late.

Planning a good estuary day out

• Allow a wide margin. Aim to be off the flats at least two hours before the route floods.
• Tell someone your route and your expected return time, and message them when you are back.
• Carry a charged phone, a walking pole and a spare layer, even on a warm day.
• Keep children within arm's reach on tidal ground, and keep dogs off the lead near channels and soft mud.
• Check the weather as well as the tide. An onshore wind and low pressure can push water higher and earlier than the table predicts.

Treat an estuary with respect and it will give you some of the best days the British coast has to offer: wading birds, wide skies, the smell of salt marsh, and a proper pot of tea when you get back. Just be off the sand before the sea comes to find you.