Tides, Currents and Wind: The Go or No-Go Call

Read the water before you commit to it.

You are now good enough to get into trouble. You can hold a line and ride out chop, so you have stopped picking spots by how safe they look and started picking them by where you feel like going. The water does not care how good your stroke is. It cares which way it is moving and how fast, and both numbers are published, free, for every spot you paddle. Paddlers who need rescuing rarely got beaten by conditions they misjudged. They got beaten by conditions they never checked.

Reading the tide

Range is the number to read first. A chart gives you the times of high and low water and the height of each. Subtract the low from the high. A 0.4 m (1.3 ft) range is a lazy day; a 2 m (6.5 ft) range means five times as much water shifting through the same entrance in the same six hours, so it shifts fast. Big ranges cluster around the new and full moon, small ones around the quarter moons. On a big range an estuary entrance can run faster than you paddle. On a small one the same entrance is a lake.

The flow peaks in the middle, not at the turn. Water accelerates from slack, peaks halfway, then eases back. The old navigator's rule of twelfths holds it neatly: across the six hours between high and low, the water moves about one twelfth of its range in the first hour, two in the second, three in the third, three in the fourth, two in the fifth and one in the last. Half the movement happens in the middle two hours. So slack is a window, not a moment: an hour either side of the turn the spot behaves like flat water, and three hours after it, the same spot is a river.

Squeeze the water and it speeds up. The tide that ambles across a wide bay tears through a narrow entrance, a bridge span or a gap between an island and the mainland. Where the map shows the water narrowing, expect several times the open-water flow and standing chop where it spits out the far end. Wide water, gentle current. Pinched water, fast current. Read that off the map before you have ever seen the place.

Wind against tide, and why it stacks up

Wind makes the chop, but the current under it decides the shape. When wind and current run the same way, the surface travels with the wave train, the waves stretch out long and low, and the day looks flatter than the wind number suggests. Turn the current around and the same 15 knots (28 km/h) builds a short, steep, breaking mess, because the waves are being shortened from underneath while the wind keeps feeding them.

Nothing in the forecast will warn you. Fifteen knots with the tide is a pleasant paddle. Fifteen knots against a running spring ebb in an entrance is standing waves, and paddlers who read only wind speed walk into it looking baffled. Check wind direction against tide direction every time. The tell is texture rather than height: wind against tide looks busy and crowded, small steep faces close together, white tops appearing and vanishing in the same place instead of travelling.

The offshore lie

Offshore wind is the only condition that gets worse as you go. On the sand with land behind you, you sit in the wind shadow of everything upwind: trees, dunes, houses, the bank. That air is slowed and broken up, so 20 knots (37 km/h) at the beach can feel like 8. Over open water there is nothing left to slow it, so the breeze rebuilds with every hundred metres you travel. The glassy water near the bank is not evidence of a calm day. It is evidence the wind is coming off the land, because it has not had the distance yet to raise chop. And you are a sail: stop paddling in 15 knots of offshore breeze and you drift downwind at walking pace without a stroke, on a board with 3 m of windage. The way home is straight into it, and the way home is the leg you do tired.

"Onshore wind takes your gear. Offshore wind takes you."

The test costs nothing. Before you commit, paddle 100 m straight upwind of your launch. If you barely notice it, the day is yours. If it is genuinely hard work while you are fresh, turn around now, because that is the easiest version of the trip home you will ever be offered.

Estuaries and rivers

An ebb tide and a river flow add up. After rain, the outgoing tide and the freshwater coming downstream push the same way and together run harder than either alone. They also push towards the entrance, which is precisely where the wind-against-tide chop lives. Upstream on the flood and home on the ebb is the classic estuary plan. Upstream on the ebb is a plan to be towed.

Rivers sort themselves by speed. The fastest water sits mid-channel and on the outside of every bend, where the flow gets thrown wide; the slowest, sometimes running backwards in a lazy eddy, sits on the inside of bends and tight against the bank. Going upstream, hug the insides and stay near the edge. Going downstream, move out to the middle and let it carry you.

Fixed objects are the real danger in current. Bridge pylons, moored boats, mooring lines, fallen trees. In moving water anything solid has a pile-up on its upstream face and a pull towards it, and a leashed board pinned against a pylon in a running tide is a genuinely serious situation. This is where a waist leash with a quick release stops being a preference. Give every fixed object a wide berth on the upstream side, and never paddle between a pylon and the bank while the water is moving.

Making the call

Decide on land, in this order. Wind direction first: is there any offshore component on my way home? Wind speed second, the honest number and the gust spread, not the number you would like. Tide third: which way is it running during my window, how big is the range, and does it oppose the wind anywhere on my route? Then the map: where does the water pinch, and where could I get out if it turned to custard? Do the hard leg first, while you are fresh, and turn at a third of your energy rather than half.

The no-go list is short. Offshore wind you cannot comfortably paddle against at the launch. A spring ebb in an entrance with the wind against it. Any current you cannot paddle out of near something solid. Fading light. If a day hands you two of those at once, the decision was made for you an hour ago. There is another tide in six hours and another sea breeze tomorrow.

Where it goes wrong

You launch into glass and cannot get home. Textbook offshore. The bank sheltered you, so you read 20 knots as 8 and paddled out through air that got stronger every minute. Fix: the 100 m upwind test before you commit, and treat glass under a land breeze as a warning rather than an invitation.

The entrance was fine an hour ago and now it is breaking. You launched at slack and stayed out into the mid-tide peak with the wind opposing it. Fix: know the clock times of the middle two hours before you launch, and be somewhere wide when they arrive.

The forecast said 12 knots and it feels like 20. Either you read the mean and the gusts are 20, or the sea breeze filled in early, which it does on hot days. Fix: read the gust number, and treat any summer afternoon paddle as a paddle in a sea breeze that has not arrived yet.

Next session, one job. Before you launch, note which way the tide is running and which way the wind is blowing. When you get back, note what actually happened. Ten sessions of that and you will read your spot better than any forecast can, because you will know what 12 knots on a spring ebb does there rather than in general. The rest of the how-to library assumes you have made this call correctly, and local conditions turn up in news.

Which forecast should I trust when two disagree?

The pessimistic one, then the water. Models handle open coast better than bays, headlands and river mouths, where terrain bends the wind in ways the grid never sees. Use the forecast to decide whether to drive there, and your eyes to decide whether to launch.

Is an offshore wind ever acceptable?

In light air, on a small enclosed waterway with a bank close downwind, with someone who knows you are out. What makes offshore dangerous is strength and distance, so remove both. A few knots across a narrow river is not the same animal as 15 knots off an open beach.

How do I tell which way the tide is running without a chart?

Look at something fixed and floating: a mooring buoy, a channel marker, a pylon. The wake beside it points downstream and the buoy leans away from the flow. Anchored boats swing to face whichever is winning, wind or tide.

Does any of this matter on a lake?

The tide half, no. The wind half, entirely. A paddler blown to the far end of a long lake by a rising breeze has the same problem as one blown offshore.