Lies, damn lies and official marina dredged depths.

[Malo37]

Unsuspecting visitor (at the visitors pontoon) at well known North Scotland marina.

 

[joha]

Re: Gosport marina dredged depths.

IT would appear the senior service plan a huge dredging operation for Portsmouth harbour thanks to someone ordering a couple of ships on steriods. Hopefully all the mud in the side bits will slide down into the hole for amny years to come.
They are taking out the minimum they can get away with and there is some thinking that this capital dredge could make things worse in the harbour.
As for Brighton they just refuse to do any dredging, there has been no dredging carried out under the east and west jetties for three years now and there are now potentially serious problems with the float packs that keep the things afloat as they are making their own little hollows in the mud with the result that many of the fittings that hold them together are missing.

 

[Pete7]

Re: Gosport marina dredged depths.

They are taking out the minimum they can get away with and there is some thinking that this capital dredge could make things worse in the harbour. .

I think there is a couple of metres of mud to come out especially along side the main jetty. They have started out of the harbour and seem to be working inwards. There is a barge moored outside the entrance now. There are also some new navigation piles going in around the harbour.

 

[Halo]

I bottomed out in soft mud for a few weeks on Conwy last year. Shortly after my sailing performance fell off. At the end of the season I found worm growing on the bilge keels and rudder in all the areas that had been in the mud and nowhere else. If you do spend time in a drying marina expect similar issues
Halo

 

[findus]

Re: Gosport marina dredged depths.

Brighton is also finally getting some dredging, currently at the entrance and the visitor berths. The backhoe dredger however can't do the rest of the berths and the cutter suction dredger which is supposed to do the job is still indefinitely delayed.

Meanwhile I'm stuck up to my saildrive's raw water intakes in the mud at low water springs - and I'm on one of the berths marked "green" on the recent survey.

Picture of entrance to Brighton from yesterday

 

[Yngmar]

Re: Gosport marina dredged depths.

Brighton has now been partially dredged - the entrance, fairway and a bit of the channel between the jetties. No dredging at berths yet, although some mud will have slid down the trenches, improving the situation for those near the dredged areas slightly.

There are now several large barges moored up to the inside of the breakwater, who will be there for some time while working on the caissons. Occasionally a rather large tug shows up to move the barges around, which means being very careful passing it. The thing has a 450 HP bowthruster which I've seen running for an hour to pin the barges against the wall while they were being moored up. It does funny things to passing yachts!

 

[Yngmar]

Re: Gosport marina dredged depths.

Doris the dredger has finally arrived at Brighton. It's an interesting contraption with a rotating bladed knob at the tip of an articulated arm and a big hosepipe at the back where the mud slurry (and ground up shopping carts, as well as my lost sockets and bits) will be pumped through, connecting to a pipeline that runs the length of the marina and then some, ending at an orange marker buoy just off the east breakwater where the mud comes out so the tide has to carry it the long way back into the entrance.

If they don't break it while laying in the pipeline (it all looked like they were very much making it up as they go along), it will hopefully start getting the mud out from under our keels very soon (I don't think it does it while the keels are in place, that'd be worrying).

 

[Dockhead]

Does any UK marina operator really know the depth across their pontoons? I have learned to never trust what I am told on arrival.

Today I got a discount on my visitor berthing fee on an already 50% discounted low season rate, when I mentioned that my keel sunk 1ft into mud that should not be there.

Ha, ha.

I've been aground three times in my present boat, in seven years and about 15,000 miles.

Once was my own damn fault, in the outer harbour of Boulogne Sur Mer, at night, at low tide, in a hurry to make it through the Dover Straits before the tide turned and ahead of a gale, and not having studied the charts sufficiently before departure. I followed my own track out and didn't see (the Navionic chart was yellowed out, but that's not an excuse) the shoals on the North side, which I didn't notice coming in with 6 metres of tide under me. What a fiasco. I threw out a kedge and called a pan pan to the French coast guard as a gale was forming, but I floated off after a little and carried on out to sea.

Another time was in Dartmouth Harbour just two metres off the visitor pontoon on the town quay. Again, right at low tide. "So you found our sand bar, did ye?" Said the harbourmaster as he floated by in his launch. :banghead:

And one more time in Dunkirk, arriving at night and -- yes, just at low tide -- after 24 hours sailing from Hamble. According to the chart and the Grande Large Marina propaganda materials, there should have been plenty of water. Not! Just three meters from my berth, our progress ground to a halt. So close, and yet so far, and after such a long passage! Had to wait about 45 minutes to float off and complete the berthing maneuver.


Harbours and marinas -- silt up. It's one of the things they inherently do. So don't believe your charts, if it's close! Not every harbourmaster will even be so honest as to tell you! The Brighton Marina materials have a disclaimer that the depths might not be accurate due to silting, and you might run aground! Pretty cheeky, eh?

 

[Birdseye]

Not really. The local university did a study of Watchet marina and if memory serves, they calculated that it gets 30 tonnes of silt deposited every tide as the incoming tide flows in carrying mud which settles at high water and isnt picked up again on the outgoing. To make matters worse, dredging is horrendously expensive and in many cases isnt allowed in order to protect bloody worms etc.

I'm wondering how long it will be before Cardiff bay silts up. River flowing into the bay but just yacht sized locks out to sea and no dredging. Some areas are already below 2m.

 

[Saguday]

We ambled up to Brighton marina from Eastbourne on the evening of Sep 1st just before 7pm (about an hour after low water) and (not having paid attention in class) was quite surprised to be told to "hang around until about 8pm" - we only draw 1.3m and it was 1m low tide.

As it was all sort of lumpy and rolly out there anchoring didn't hold much appeal so we just bimbled about at a knot or two trying to keep warm.

At 8pm I asked if they had any water in their marina and they said yes plenty so in we went, without any particular issue except the lumpy rolly stuff beam on to you just as you go in the quite narrow entrance - this was our first time there but looking at it this must be fairly typical.

Had a good time though - staff were good and we enjoyed the town - so glad to see they've got the dredging underway at last.

 

[prv]

Re: Gosport marina dredged depths.

Doris the dredger has finally arrived at Brighton. It's an interesting contraption

Indeed - interesting to see that the spuds seem to be able to tilt, or swing back and forth under hydraulic control. Is this so that it can walk along the bottom?

Pete

 

[Yngmar]

Re: Gosport marina dredged depths.

Indeed - interesting to see that the spuds seem to be able to tilt, or swing back and forth under hydraulic control. Is this so that it can walk along the bottom?

I believe that's so the whole thing can rotate by moving them in opposite directions, so it can dig a wider arc before having to redeploy them.

Those two "wide" bits at the sides (where the guy in the high-viz is standing on) also are hinged and have a hydraulic ram, looks like they can swing forwards to make the thing longer, narrower and have more buoyancy forward where the arm is. The cockpit has lots of buttons and levers and two joysticks at the pilot seat.

 

[laika]

We ambled up to Brighton marina from Eastbourne on the evening of Sep 1st just before 7pm (about an hour after low water) and (not having paid attention in class) was quite surprised to be told to "hang around until about 8pm" - we only draw 1.3m and it was 1m low tide.

I called them on the 2nd to ask how deep they were now dredged to and they said minimum 1.5m below datum in the entrance and main fairway which was consistent with what the depth sounder as telling me coming in. Given that the shallowest bit isn't right in the entrance where it's rolliest, that sounds like quite conservative advice.

 

[Saguday]

Sorry I was repeating myself, hence the deletion

In retrospect and knowing what I know now we should have gone in to get out of the slop and then hung around inside a bit until it was a bit deeper.

 

[Angele]

In retrospect and knowing what I know now we should have gone in to get out of the slop and then hung around inside a bit until it was a bit deeper.

No. I think what you did was correct. You really wouldn't want to be aground in the approach to Brighton marina, even in reasonably benign conditions. The waves bounce straight back off the wall at you and that could be really dangerous.

If the marina had warned you to hang off, then what you did is surely the safe option. It sounds like they were probably wrong in that advice, but to go ignore it and go against what they had advised (unless you were VERY sure of the depths all the way in) would be a very foolish IMHO.

 

[Lucky Duck]

A friend went aground in the approach to Brighton Marina resulting in it being booked for a lift out to look for any damage the very next day