Lies, damn lies and official marina dredged depths.

[jonjo]

When I was a marina manager, we had a plan which showed a sounding for every berth, which was compiled annually by chugging around in a small boat with a decent instrument hanging over the side.

Which begs the question, was this data disclosed to customers?

Or even, did parttime summer staff see this data? I have lost count of the number of times a youthful voice on channel 80 has assured me with complete confidence that the marina is dredged to 2.5 meters.

 

[dnickj]

Victoria Harbour Guernsey were the worst we found for this fibbing last year. Insisting our berth was over 2m deep even though we were hard aground and waterline 6 inches above water level

I can vouch for that in Guernsey as well - there is even a picture of us on the cover of last years visitors guide and in this months marina cost article in YBW - i have complained on a couple of occasions only to be told that i was welcome to go elsewhere - but not at low water !!!

 

[Yngmar]

When I was a marina manager, we had a plan which showed a sounding for every berth, which was compiled annually by chugging around in a small boat with a decent instrument hanging over the side.

Just such a chart hangs in the Brighton marina office, by the radio operator's wall, and thus publicly viewable.

And yesterday a small powerboat puzzled me by its odd behaviour - it passed my transom with about 10cm clearance and proceeded to do so for every boat down the pontoon. It only made sense when I noticed the big GPS rack on the back of it and the letters "SURVEY" on the side

So I guess there'll soon be an update to that chart, and hopefully actual dredging rather than just pictures of a dredger that Premier supposedly acquired for the task. I think perhaps the fact that the east jetty itself (the one with the shower blocks and tin huts on top) ran aground last week might've caused a bit of a (much needed) wakeup call.

 

[laika]

Latest notice at Brighton is that boats with draft > 1.5m may have their keels in the silt on the visitors' pontoon at low water.

We had a nice sail round on a neighbour's boat yesterday waiting for enough water at the entrance to get in. It would have been less nice in inclement weather.

 

[dom]

Latest notice at Brighton is that boats with draft > 1.5m may have their keels in the silt on the visitors' pontoon at low water.

We had a nice sail round on a neighbour's boat yesterday waiting for enough water at the entrance to get in. It would have been less nice in inclement weather.

My goodness, what was yesterday's low tide; 1.8m over LAT? Depending on your draught this suggests that the harbour entrance may still be near drying at big springs

...and that's after last year's dredging!!

 

[laika]

My goodness, what was yesterday's low tide; 1.8m over LAT? Depending on your draught this suggests that the harbour entrance may still be near drying at big springs

Friend's boat's draft 1.9m. Marina advised 1.8m depth at the afternoon (1.5m) low. My own thought would have been "it's pretty calm and only a bit of mud" but friend had just anti fouled his keel and it was a nice day for a few practice manoeuvres.

 

[doris]

Does anyone have any idea what difference the dredging of Portsmouth Harbour for the carriers might have for the marinas? Logically all that stirring up of mud will result in the marinas getting even more clogged up!

 

[Yngmar]

Friend's boat's draft 1.9m. Marina advised 1.8m depth at the afternoon (1.5m) low. My own thought would have been "it's pretty calm and only a bit of mud" but friend had just anti fouled his keel and it was a nice day for a few practice manoeuvres.

Results of the survey I'd mentioned above are now available in the marina office. Well worth a look. I'm currently in one of the green marked areas (0.7), and my keel sinks 1m deep into the mud according to my own lead line at the last springs low tide. And many berths are marked in orange and red.

This bothers me quite a lot, because it means propeller, saildrive and the precious little water intake holes on the bottom of the saildrive are in the mud. A few days after every springs tide, I now get to run the engine and clean the raw water strainer. Last time it had a tiny orange baby crab, along with some shell fragments and other crud that I don't need fouling up the leg

As for "only a bit of mud", if you go for a wander at springs low tide, in addition to pontoons and boats sitting on drying mud, you'll find there's all kinds of stuff down there, including a section of galvanized steel building site fence that seems to have blown off the breakwater. That's by the bend at the corner of pontoon 25. And while less likely on a sailboat, there was a small powerboat a couple weeks ago that had managed to pick up the chain of one of the channel markers with its prop and moored itself that way.

The current story is that the cutter suction dredger being built for Premier in Italy is being delayed (and when finished, it'll not instantly teleport to the south coast either) and the backhoe dredger for the entrance was fully booked so it won't come around until May. Maybe.

 

[johnalison]

When Brighton had closed off half the harbour for dredging in mid summer a few years ago we enquired why they didn't do it in the off-season. We were given to understand that they weren't allowed to dredge in the winter as it was a spawning ground for bass. I don't know how true this is, but it must make dredging the pontoons difficult if so.

 

[Pete7]

Does anyone have any idea what difference the dredging of Portsmouth Harbour for the carriers might have for the marinas? Logically all that stirring up of mud will result in the marinas getting even more clogged up!

QHM dug out a huge chunk of Haslar Creek a couple of years ago in preparation, I think they had some spare money so spent it so the creek doesn't all slide into the main channel when they dredge that. Premier had the dredger in last year and the RNSA dredged Cold Harbour the year before. The problem is if you want to build a marina were nature intends to put a mud bank then you will either loose or it will be expensive. Dredging further up the harbour ran into problems of contaminated mud under clean mud so "no touchie" until someone battled their way through the treacle of licencing and permissions required for dredging.

Begs the question what they will find at the bottom of Portsmouth harbour when they start on that. Antifoul paint struggles at present, add a nice soupy mix of disturbed mud and it's going to be a tough few years. Shares in the Haslar Sealift could be a good investment especially now they can do bilge keels

Pete

 

[Otter]

Is Brighton now a half tide marina? Asking because we stop there on the way too and from the Solent each year.

 

[laika]

Is Brighton now a half tide marina? Asking because we stop there on the way too and from the Solent each year.

Well it certainly isn't all-tide. Last month a notice said that vessels with a draft exceeding 1m shouldn't enter 120 minutes either side of low water and (which might mean "or") call for depth advice:
https://premiermarinas.com/Marina-News-Events/Mariner-Notices/2016/March/Brighton-Marina-Notice-to-Mariners-9-of-2016

120 minutes for a bit over 1m would be rather conservative, but most fin keelers aren't going to get in or out at low water.

Times for the yacht club's sunday morning racing are adjusted to avoid starting or finishing too close to low water.

 

[Otter]

We are 1.4m so that outs us three hours either side, or half tide. Ouch.

 

[laika]

We are 1.4m so that outs us three hours either side, or half tide. Ouch.

Call 'em but you'll probably be OK an hour either side and if my rough calculations based on observed depths an hour after LW yesterday were right you'd make it in at low water neaps.

 

[Angele]

Call 'em but you'll probably be OK an hour either side and if my rough calculations based on observed depths an hour after LW yesterday were right you'd make it in at low water neaps.

Brighton

I have just spoken to them, because I'm planning a trip there next month. Despite what the NTM says, his advice was that LW +2 to LW -2 was fine for any vessels over 1.5m draft (but presumably not vessels of any draft...). Apparently the depth on the visitors' berth varies from 2.0m to 0.2m below CD, and it sounds like the 2.0m end is full with commercial vessels at the mo.

He said "we dredge the entrance channel to 1.7m below CD." He didn't rise to the bait when I said "sure, but what I want to know is how much it has silted up since you last dredged".

I draw 2.1m

Fortunately, the lowest tide while I plan to be there is 1.3m, so I'll only be 60cm in the mud. :nonchalance:

 

[laika]

He said "we dredge the entrance channel to 1.7m below CD." He didn't rise to the bait when I said "sure, but what I want to know is how much it has silted up since you last dredged".

We came in about an hour after low water (day after neaps). I think 2.1 was the lowest depth we saw in the entrance while sticking to the middle of the channel. Of course I can't vouch for the accuracy of my friend's sounder (he's sure it's set for depth of water and he seems to know what he's doing) and there's a lot of potential inaccuracies in my calculations but that certainly makes less than half a metre below CD. Anyone else want to share your guesstimates of entrance lowest depth please do

 

[dom]

I draw 2.1m

Fortunately, the lowest tide while I plan to be there is 1.3m, so I'll only be 60cm in the mud. :nonchalance:

One word of caution here -- most people are fairly sanguine about dipping their keel in the mud and rightly so. A bigger danger emerges when its time for a spade rudder to bottom out. My depth is a tad more than yours (2.4m and 1.9m rudder), but I'd be seriously worried about pushing the rudder into one of those metal fences Yngmar refers to in post #28.

The trouble is whilst most rudder stocks will have hefty design tolerance when stressed in the lateral plane, vertical plane tolerances are another matter. So I'd prob take a good look at how vertical loads will be dissipated through your hull before your rudder gets anywhere near the bottom.

Incidentally I've just had new top and bottom bearings from Jefa -- I have also taken up home brewing to save the remaining beer tokens :ambivalence:

 

[dunmor]

Eastbourne entrance is just as bad, 1 hr each side, quite a few boats been grounded, dredging is to start in may, marina is nice and deep thou.

 

[pgtips]

Eastbourne entrance is just as bad, 1 hr each side, quite a few boats been grounded, dredging is to start in may, marina is nice and deep thou.

Eastbourne is normally good though to be fair but the rough weather this winter has resulted in shingle building up very quickly. Seems it wasn't that long ago they cleared one build up and then it was back again after some winter storms. They do dredge the entrance channel annually and I'm not aware of any problems in the marina itself.

 

[Otter]

They're good people at Eastbourne