Why would you build a breakwater that floods on spring high tides?

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fredrussell

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The Harwich Breakwater near me disappears below the surface on spring high tides. I get that if you’re maintaining a watch and doing things properly it’s entirely your fault if you run in to when it’s submerged, but I can’t understand why they didn’t build it a bit higher so it’s always visible, or at least in daylight hours. A few boats have run into it over the years, I’m told. Is it just a cost saving thing or are there other reasons to build it this way?
 
fredrussell said:
The Harwich Breakwater near me disappears below the surface on spring high tides. I get that if you’re maintaining a watch and doing things properly it’s entirely your fault if you run in to when it’s submerged, but I can’t understand why they didn’t build it a bit higher so it’s always visible, or at least in daylight hours. A few boats have run into it over the years, I’m told. Is it just a cost saving thing or are there other reasons to build it this way?
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It does a good job, for what it was built for, at it's current height so I think they made the correct decision.

www.solocoastalsailing.co.uk
 
Graham_Wright said:
Plant a sticker-upper on it?
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You cannot win.
The Submarine barrier off Southsea has sticky-uppers on it but it was recently hit by a yacht:
https://www.islandecho.co.uk/bembridge-lifeboat-responds-to-mayday-call-from-yacht/

Also 2 days later, over the last BH weekend, a large mobo hit Bembridge ledge at 20 kn:
https://www.islandecho.co.uk/motor-cruiser-damaged-after-hitting-bembridge-ledge-at-nearly-20-knots/

And the following day another hit Goose rock off the Needles:
https://www.islandecho.co.uk/sunseeker-motor-boat-hits-goose-rock-off-the-needles/
 
Sandy said:
Plymouth is the same and has been there some time.
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I've never seen Plymouth breakwater underwater due to tide (I've seen waves breaking over it). It's not marked on the chart as drying and I'm sure it's above HAT.

Having said that I have seen it when it *looks* to be covered as you approach due to high tide and big seas breaking onto/over it. As an aside, I know the cage on the Eastern end is supposed to be for shipwrecked sailors, but if I'd run a boat into the breakwater in a gale I wouldn't fancy my chances making my way along the top in breaking waves to reach the ladder up to it...
 
Harwich breakwater has a perfectly good lit beacon on the end, it is only a problem if you were tempted to cut the corner too close when coming from the Walton Backwaters. I have some years ago seen a yacht beating in, perilously close to the breakwater, execute a crash tack when it was obviously spotted almost too late.
 
I am guessing that it doesn't need to be higher to break the waves, but it would have cost more to build it higher.

It's not just a matter of adding some height to the visible bit: you would also need to raise the whole of the slopes either side that support it.

Or maybe it was designed that way so that you lift-keeler types could skim over the top, thus avoiding the hazards of all the pot buoys beyond the end of it! ;)
 
LittleSister said:
I am guessing that it doesn't need to be higher to break the waves, but it would have cost more to build it higher.

It's not just a matter of adding some height to the visible bit: you would also need to raise the whole of the slopes either side that support it.
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+1
And possibly to minimise weight on the seabed if it is soft and not good at supporting heavy weights.

Good engineering = doing for £10 that which any bloody idiot could do for £20.
 
From «*The Excursionist’s Guide to Harwich*» (1865):

Harwich Harbour is well known as being easy of access, capable of affording anchorage to hundreds of vessels of all sizes, and perfectly protected against the most boisterous weather; and the Government of the day has never failed to recognize its importance in a national point of view; hence it is that no less a sum than £l32,000 has been expended in constructing the magnificent Breakwater, and in removing certain shoals or banks which obstructed the free navigation of the harbour - works which were in progress from l840 to l856; and since the cessation of hostilities with Russia, and the transfer of the Coast Guard from the Customs to the Admiralty Department, Harwich has been made the head-quarters for the extensive district between Great Yarmouth and Dover.

Plymouth Breakwater was started at the same time but finished sooner:

https://en.wikipedia.org/wiki/Plymouth_Breakwater

Both protect what were very important Naval bases in the era of the sailing Navy.

Harwich Breakwater exists because over enthusiastic dredging for coprolites (dinosaur shit)for use as fertiliser had damaged the deep water channel.
 
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DJE said:
+1
And possibly to minimise weight on the seabed if it is soft and not good at supporting heavy weights.

Good engineering = doing for £10 that which any bloody idiot could do for £20.
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That's not true - actually an engineer can do for a tanner what any fool can do for a bob!
 
Isn't that what's called a training wall? A breakwater is wall with sea on one side and dry land on the other. There's one at Pwllheli. ANY SWELL is stopped without building the wall any higher at extra cost. The crest is slightly submerged at HW but the end has a marker. I've never seen any boats stuck on top.
 
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