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In the fifth instalment of our Sea Signs series William explores what you can learn by looking at structures on the beach 



My favourite structure is the pier, and one of my Top 10 is the one in Deal – mainly because the architecturally acclaimed timber and glass pavilion at the end of its 312 metre walkway is home to the Deal Pier Kitchen, where I used to write in the mornings while gazing out at sea. Waves would surge beneath my feet, clouds swirl past the windows, and there I would sit with my coffee, pen and paper - simultaneously immersed in nature and shielded from it. But what really draws me to piers is that they take you away from the land and life’s little problems, without having to squeeze into a wetsuit, pump up a paddleboard or plan a sailing passage. In just 312 windswept paces you can step back and dream big. 


Piers are practical too. Whenever I pass a pier I look at the legs to check the tide. The high water mark is clearly defined by the transition from dark barnacled growth below to the smoother, lighter concrete above. By observing how much dark leg is exposed I can work out the approximate tide height; in Deal it can range by 6 metres, or the height of a two-storey building. The three tiers provide a reference point too. Through the engineers’ miscalculation the lowest tier is underwater 30% of the time; when the tide is 4 metres the level becomes flooded. It takes a 7-metre tide to cover the middle tier; on the rare occasions this happens the sea is dangerously high and the town is at risk of flooding, so batten down the hatches!


The pier also tells me which way the currents are flowing. When water hits an obstruction like pier legs or a post in the water it is compressed and flows past at accelerated speeds. This leaves an area of low pressure immediately downstream of the structure and nature maintains equilibrium by creating a counter-current pushing water upstream to ‘fill the gap’. Where this slow-moving eddy meets the fast-flowing current, the two streams collide and create turbulence. This is called an eddyline. Sometimes they look like shadows running from the base of the obstruction, but often the sun is in the wrong position and you can be confident it’s a clue to the currents.


In extreme cases eddylines can create whirlpools capable of sucking a swimmer down to the seabed; the biggest maelstroms in the world grow to 10 metres in diameter and extend 100 metres beneath the surface. So stay away from big rocks or bridge legs in areas of strong currents! Fascinatingly, tidal whirlpools can be observed in central London. Although the capital is 50 miles from the coast, a rising tide at sea creates a huge 7-metre range at Tower Bridge with strong currents flowing upstream against the rivers’ natural gravitational flow. When these currents collide with the bridge legs you can clearly see the eddylines and small whirlpools. 

“in extreme cases eddylines can create whirlpools capable of sucking a swimmer down to the seabed”

On a larger, but gentler scale, the eddy concept happens where coastal structures are built at right angles to the prevailing tidal currents. Brighton pier is a perfect example. Although it is not a solid structure, there are so many legs that it has the effect of a ‘wall’ with tidal currents deflected to the end of the pier, where streams are accelerated. Just downstream of the pier an eddy forms. Swimmers and paddle boarders on my Tide Walks have noticed that the currents are often different on either side of the pier - this is why. So if your Tidal Compass or Imray Tides Planner App is saying the currents are flowing one way, but they are actually taking you the other, look around for coastal structures [or the natural geography of the coast] because chances are you’re in an eddy.


When I lived in Deal I would try to swim in the sea every day at 12:00. This would give me something to get excited about throughout the morning and re-invigorate me for the afternoon. A series of posts running along the beach proved invaluable to the success of these swims - each for its own reason. One is where my swim buddy Danny left his flip-flops so they could be easily found after [no simple feat on a long pebble beach]. Another is home to a semi-resident Cormorant who faces into the wind to dry his wings – our natural wind vane. The most useful structure has a rope dangling from it, pulled away from the post by the current and pointing us in the direction we should swim if we want to go with the flow, or challenging us to go the other way if we want to test our stamina by swimming into the stream. Finally, there’s the destination post that we set our sights on, not stopping until we got there, then clinging to it with all our strength as the currents raced past like a raging river in full flood. 


One way to avoid this battle with the tidal currents is to head to your nearest tidal swimming pool. The design of these structures allows the flood tide to pour over the walls, which then hold the water in as the tide ebbs away. One of my favourites is Walpole Bay, Margate, and it’s the largest in Britain, covering a huge 4-acre expanse. It was opened in 1937 so the local population could swim at low tide without having to trudge through mud over the slippery chalk reef. 


You can find tidal pools all around the coast and they are usually built where sea swimming is challenging – either because of the tide or the waves and rip currents. For this reason many are found in the wilder corners of the British Isles; Cornwall, northern Scotland, north-east England. With many built in the 1800’s and early 1900’s, their hard stone walls are softening around the edges, seamlessly blending into the coastline and becoming a natural part of the environment, perfectly positioned to give us safe sea swimming all year round. But at high tide, when the sea surges over their walls, they are less protected than at Low Water, when they sit like their own little seas, free from the crashing swell.

In the next Sea Signs feature William will discover what you can learn by observing the behaviour of birds.

About this series

Every day the sea is different, a  result of the ever-changing interaction between the moon, sun, tides, wind, waves,  buoys, boats and the beach. While the picture may appear complex, like a piece of classical music, it is essentially just an arrangement of simple elements, or notes. By dismantling the machine into its component parts and exploring each one in detail we can create order out of chaos; clarity out of confusion. That is the  purpose of this series 'Sea Signs'.

When we are young we learn to navigate urban environments; what traffic lights  mean or how to cross a road. What many of us aren’t taught is how to read nature’s  signposts; how to judge wind by watching birds or what weather different clouds  bring. Then there’s a whole technical world of buoys and boats with different light  sequences, colours and signals communicating messages. My goal in this series is to  share with you all the signs – both natural and man-made - that you may encounter in  your adventures along the coast so you can read them as well as any yachtmaster  skipper or crusty old seadog. 

With this knowledge, nothing is going to slip under your radar.

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