Sub Barrier - Solent - How Deep?

toad_oftoadhall

toad_oftoadhall

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From random observations around about low tide I reckon the section of the Submarine Barrier South of the Dolphin currently dries deeper than about 1-1.5mCD (Closer to 1 than 1.5 IMHO but a margin for error won't hurt).

Anyone observed the depth more scientifically than me and able to give an accurate depth - or even know the depth from some official source?
 
I have never seen the top of the barrier between the main passage and the fort, even at low spring tides. I used to pass through regulary on my way in to Langstone Harbour.



The barrier shows near the inshore passage, but there is usually enough water in the gap for shallow draught boats.
 
Yes, the slabs do dry about 1.0m above datum. So tell me why thousands of boaters like myself, quite capable of simple tidal calculations, persist in going thro the Dolphin Passage or the Small Boat gap by the beach (least depth just over a metre) but never straight over!
Incidentally the blocks are about 30ft long and about half that distance apart. I have pics -and cuttings of boats sinking!
 
We use the inshore small boat channel off the beach from time to time, rather than the middle or main channel.

Must say we've never worried about how much water over it, more which gap could we make in the weather conditions and were we lined up for it ok, day or night.

Both the small boat channels lights can be hard to see when it's a bit rough against Pompey's lights esp at night and HWS high water, when the dolphins don't stand out so high and well against the sky. can be twitchy at 02.00/forums/images/graemlins/grin.gif
 
So why do want to know? The assumtion is that you intend to try to go over it. Don't - even in a rib. There's no point since there are several reasonable passages through.

I put a pump on board a 27' lift keel that tried a few weeks ago. Luckily the split in the keel box didn't ship too much water before we got him lifted. Could have been much wetter though not to mention the cost.
 
There was a mayday a few weeks ago when someone hit it. I remember it was low water Springs. The yacht, if my memory serves, stopped with such force that it threw a crew member against something, and she had to be lifted off and taken to hospital. I listened to the whole thing. Poor guy. I suspect it was his partner or girlfriend who was injured.
 
It's a fair point though and something I have often wondered myself.
It would seem that at high water or thereabouts it would be perfectly safe to go across the barrier as even at HW neaps there should be at least 3 M over the most dangerous part of the barrier.
However even knowing this I still err on the side of caution even in flat conditions and go through the passeges.

I suppose it is just the fear of the unknown and not having complete confidence in one's calculations and it just seems to be an unnecessary risk as there are 2 passages through it. I've even accidently drifted back over it after going around the fort when caught unawares by the tide approaching low water with a 2.1 M draft.

Not a good idea I know!
 
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So why do want to know? The assumtion is that you intend to try to go over it.

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Way, way, way too late!

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Don't - even in a rib. There's no point since there are several reasonable passages through.

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There may not be a dramatic disadvantage to going through the official passages but I can't really see that there's any disadvantage to going over if the sea state and tide height is suitable.
 
A couple of weeks ago I watched a small fibreglass cruiser go straight over it at 20kts+ about 3 hours after low water. I wasn't sure if he:
a.) had done the tidal calculations and was confident of his draught at planing speed
b.) was a local expert, could see the blocks and aimed for a gap
c.) had no idea what a chart was, and was blissfully unaware

In the event, I started breathing again when he had cleared the line of yellow markers without mishap.

dv.
 
I recall this sort of conversation in a pub with a fisherman when I was a regualr Solent boater. He did advise that the Barrier collects some of the semi floaitng debris in the area and in his opinion you have a higher chance of snagging some old net etc. Whether or not he was shooting a line is up to the individual skipper but I only ever went through the passages in anything other than a dinghy or kayak regardless of the state of the tide.
 
There are a million and one hazards that are safe to cross at high water like the wreck off the Needles but I still prefer to go the safe routes ! Saying that I'm quite happy to use all of Chi Harbour when sailing !

However, do any pilot books say the barrier can be crossed safely ?
 
No, they don't, as far as I can remember. Even "Solent Hazards" was wary of advising us that it was safe to go inshore of the fort on the Island side until QHM cleared it - and it was probably perfectly safe before that. The Main Passage is pretty well placed for trips between Chi and Pompey anyway, which is a well-worn route - if you go much further to the north you can get tangled up in the sandbanks off Langstone Hbr.
 
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