Last weekend we were staying with friends not so far from the Mont Saint Michel, and for some reason talk turned to the tides in that bay. Of course, they come in faster than a galloping horse, someone said, and we all nodded in sage agreement. After all, everyone knows that.
I was nodding too, but later I thought: Well - Really? it’s a very common claim, made for many locations. Of La baie du Mont-Saint-Michel itself, the tide comes in “as swiftly as a galloping horse” – according to Victor Hugo (ahem).
Elsewhere, the Queen’s Guide to the Kent Sands of Morecambe Bay (Lancashire, England) tells us: “It is the most dangerous bay in the world out there. The tide comes in faster than a galloping horse.”
I could go on. How fast does a horse gallop? North of 25 mph, it appears. So is there credible evidence that, anywhere in the world, the tide comes in faster than a galloping horse? I’m guessing not (but would be enchanted to find out that somewhere it was true). And if not, where is the fastest tide and how fast is it?
I’m putting this in GQ as I’m after a factual answer. But finding facts seems mighty difficult on this subject so, Mods, please feel free to move it to IMHO if it becomes obvious that’s the better home.
The phenomenon is known as a “Tidal Bore.” Speeds for some of the largest are in the 12 MPH (Turnagain Arm, Cook Inlet) or faster. This site claims 24 MPH for Turnagain’s. This link of a 1982 Scientific American article mentions the mightiest tidal bore being along the Tsientang or Qiantang River. It can flow at 15 knots, and the wave may be several meters high. Tourist attraction these days.
Tidal bores can vary significantly in speed and severity, even along the same body of water as seasonal changes occur, the waterway gets dredged or the shoreline otherwise altered. In the Sci. American article link, the bore mentioned by Hugo on the Seine is almost non-existent these days, as the shoreline has changed and the river dredged.
Interesting. Now, when I think of (tidal) bores I think of, say, the Severn Bore (video), which is very different to “the tide coming in” across a bay. However, I note that in the link you provided there is a photo of a bore in Morecambe Bay, which is actually one of the locations I quoted, and where the Queen’s Guide to the Kent Sands talks of “faster than a galloping horse”. But, somewhat like the Severn Bore, this appears to be a bore wave rushing up a (filled) water channel. So I wonder if there are two separate things going on here. No question that the tide in Morecambe Bay or around Mont Saint Michel comes in a very long way (and therefore quickly) - and I had assumed Victor Hugo was talking about the speed of that. But I see there also a bore in that bay, and could that have been what he was talking about?
Just looking at the Morecambe Bay photo, that bore is running in a very flat area, and I could imagine water overflowing onto the sands - but surely if that happens it dissipates the size and speed of the bore?
So in practice are there two different things to consider - a person on a sand/mud bank digging for cockles, who is unlikely to be outrun by the tide; and another digging on the side of one of these channels who could be taken by surprise by a bore?
It’s the flatness of the beach that causes the phenomenon. A small rise in the water level = a very long run ‘up’ the beach. Here is a better explanation from Morecombe:
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I used to live near Pendine Sands where cars were allowed to park on the beach. It was not uncommon for a car to be trapped by the tide - we had at least two or three a year.
In one of Andrew Zimmern’s shows they were clamming on a huge tidal flat. The locals mentioned that several people a year were lost there as by the time you noticed the tide washing close to you it was too late to make it back.
So “faster then someone wearing floppy boots in the mud”
It’s kind of a poor comparison, as horses, being proportionately very heavy for their small hard feet, are helpless in mud. Their best bet would be swimming, not galloping.
I’ve witnessed the tide at Fundy – not the river bores but just mud flats which go nearly to the horizon, silently being covered in water. It’s eerie.
When I visited Mont St Michel the signs warned about wandering the tidal flats around the mount unless you knew the tides very well. But… I do have a photo from the top of some people wandering around the tidal flats. I hope they knew what they were doing.
I read somewhere that the causeway and parking area had messed up the water flow and the tides were not as bad as in historical times - but that the plan was to replace the causeway with an elevated tram, so the water could flow freely again.
What does happen (it sometimes happens on Sandymount Strand in Dublin) is that people get outflanked (not outrun) by the rising tide. The sea quietly fills a channel behind them. By the time they realise their predicament, they are on an “island” which is surrounded by waist-deep water and is rapidly shrinking.
I suspect this is also what happens in Morecambe Bay - I find it very hard to believe that the actual speed of advance of the tide across the shore ever exceeds walking pace. But a channel can fill quite rapidly.
The tidal range in Dublin is about 4 to 5 meters. On the Channel coast of France it’s about double that. About half of that rise happens in the 2 hours around mid-tide. Call that 2 meters per hour change in level. For that to translate into a “galloping horse” speed of say, 20 km/h over ground, the strand would have to be flat to a tolerance of about 1 in 10,000 and the distance covered by the sea during those 2 hours would be 40 km. I doubt if there is anywhere in the world that meets those conditions but I could be wrong.
I should have read the article on tidal bore before replying. Judging from some videos, there are some places where the tide advances over the sand faster than walking speed.
Gray Ghost’s link on tidal bores states that the river Sée off the Bay of Mont Saint Michel has a bore, so I went looking for video. (I know Avranches well, and you can see the river from the public gardens (Jardin des Plantes), and frankly a less likely candidate for a bore would be hard to imagine.) Haven’t found one, but poking around, I found this news article from just a few days ago: it says (my ropey translation) From Saturday 28 Sep to Wednesday 2 Oct 2019 the Bay of Mont Saint Michel will be witness to the High Tides. The rising tide will be preceded by a bore. A spectacle visible in various places in the bay.
I have to admit, I had no idea that there were bores to be seen in the bay, let alone (at least on occasion) in multiple parts of the bay. What’s particularly interesting is that the photo looks like a bore running over mud flats; I presume it must be in a channel (there is water either side of the kayakers), but I can imagine how you (or for that matter, Victor Hugo) could see that and refer to it as “the tide coming in (fast).” Here’s a video of a bore in the Bay of Mont Saint Michel. Check out around the 2.00 mark - the width across the wave is remarkable.
I think so far we’ve established that a tidal bore can come in with a speed comparable to a galloping horse. And it can be really wide/extensive - much moreso than I would have imagined.
If you look at Morecambe bay on Google Maps, there are places where you could easily walk out 5 km from dry land at low tide - just because the mud/sand flats are so extensive.
Certainly it’s possible to be cut off by a channel filling behind you - the satellite view also shows there are lots of channels and banks, but the location of the bay is also in a westward-pointing channel - not as much of a channel as the Bristol Channel, 300 miles to the south, and not as exposed as the Bristol Channel, but it still has a tidal bore for the same reason there is one at the Bristol Channel.
Basically, if you’re way out there on foot and the tide starts lapping around your feet, you are in great danger - the tide will cover the sand faster than a human can walk, especially as it’s turning the sand into quicksand as it comes in - so although you are trying to walk/run inland, the water is getting deeper around you, and the footing softer
The most scared for my life I’ve ever been was at Morecambe Bay. My and my brother weren’t out any great distance, but that water comes in rapidly and in very disorienting fashion. We never told our mum and dad why we were so wet and dirty that day.
I don’t know if it is literally at fast as a horse, but the tide at the Broomway trail is reportedly substantially faster than a human - I can’t find anything indicating what speed that actually is, but I bring this up because it’s a fascinating phenomenon in any case.
This is a little off-topic, but this link goes to a page all about the historic routes across Morecambe Bay and Lancaster Sands from Lancashire to Grange-over-Sands and Ulverston on the Cumbrian side.
If you scroll past the various paintings of people out on the sands to the bottom of the page, there’s a document available as a slideshow of an old history of the crossings going back to pre-Roman times. I had to increase it’s size to read it but found a lot of fascinating info there…
I didn’t see anything about galloping horses though!
I think it is more the fact that the topography is so flat and complex that the tide doesn’t just come in towards you: it can surround you from multiple directions before you even notice. So the speed doesn’t necessarily have to be that fast, just faster than you will notice.
Your earliest cite is Victor Hugo, who died in 1885. A galloping horse would have been the fastest mode of transport you could have on a tidal flat at that time.
Couldn’t that phrase be a figurative warning that “you can’t possibly outrun the tide here, no matter your conveyance?”
I’m not convinced that it’s meant to be taken literally. I’m no equestrian, but would a contemporary of Hugo’s expect that a horse could gallop on a mud flat? Some tidal flats are firm, but can one safely assume that a particular mud flat could support the weight of a galloping horse without causing the horse to fall?
Maybe I’m way off base, but this sounds like a metaphorical warning (”No matter what you think now, you won’t outrun the tide here.”) that morphed into received wisdom now taken as fact. Is there any evidence that tbe warning wasn’t originally meant figuratively?
Seeing that this equates to a little over 10 miles an hour, it would be more accurate to state that a tidal bore can reach the speed of a hobbled old nag.
