Beware charted depths on the SW Sunk

[tillergirl]

I am posting this really on behalf of Steve and Heather (Dabsolute470). It has been mentioned in one or two posts as a bit of Fred Drift but merits the clarity of its own thread. Steve and Heather particularly want all the forum to know of the danger.

Steve and Heather were heading on Friday 29th July from North Fambridge on the Crouch to Ramsgate. Coming down the east side of the East Barrow sands, they crossed the Barrow Deep and carefully started crossing the SW Sunk - and went aground! This despite passage planning and thought over the crossing point that they had used before.

The problem is that the charted depth at the point they went aground was shown as 3.7m. Having watched the tide continue to leave after they touched, we have their mark one eyeball observation that instead of 3.7m, there is 6 to 8 inches at that spot and a significant drying patch immediately ahead of them. This knoll is steep to which means that there is little advance warning on the echo sounder.

This differs from the charts. It doesn't matter whether you use Admiralty or Imray derived material, they are obviously using the same source data. There is absolutely no question that Steve and Heather did not know where they were. We can be quite sure of the plot as all the data hangs together.

Can we suggest that anyone who crosses the Sunk Sand makes a note of the position: 51.37.420N, 001.15.800E - currently nicely marked by a 3.7 which you ought to put a line through.

What about my chart of the area? Unfortunately Steve and Heather had not seen it in advance - they now have an A3 sized version! This knoll is marked, not fully as I couldn't get over it to sound it but the extremities are shown. The Swatchway that my chart shows is there but unfortunately they were just a little too far NE - why wouldn't they be as that's where the chart shows the best water. Just as added reassurance, Vamoose of this parish has successfully used the swatch two days before Steve and Heather's trouble and two hours before HW had not less than 4 metres.

The chart is available at http://www.eastcoastsailing.co.uk/ and then onto Navigation - Chartlets.

Thanks are due to Steve and Heather - who returned safely to their home berth - for wanting everyone to be warned about this.

PS We have advised Imray who will be including this is a NtM and also the UKHO.

 

[pyrojames]

I have been crossing sw of the old sunk beacon and found plenty of depth there. Have I just been lucky?

 

[DanTribe]

I propose a vote of thanks to Steve & Heather for services to sandbank dodgers.

And to Tillergirl, naturally.

 

[FullCircle]

We had a big weather month in August 2008.
We went to Ramsgate Week via that route, and crossed at half tide with 2.3m clear in F6 or so.
We left the GPS track on the chartplotter.
We had a torrid week of gales and returning to Burnham 6 days lateer we crossed at the same state of tide, but saw water breaking on sand on top of our previous track. No water there at all, but we crept over a bit to the North.
It moves, a lot, especially during lots of extended weather.

 

[dabsolute470]

Hi tillergirl (Roger),
thanks for the posting and hope its helpfull to others also the chartlett you gave us sunday.

 

[tillergirl]

I have been crossing sw of the old sunk beacon and found plenty of depth there. Have I just been lucky?

Maybe, maybe not. Depends how far away from the old beacon you were. Thinking back quite a while there used to be shallow stuff away to the SW from the crossing point that was itself SW of the SW Sunk beacon. But as observed it changes!

While I was doing the runs backwards and forwards in May - which was a lovely sunny day, I intially had a flat calm; ideal for the purpose. After about an hour a sea breeze came up from the South East and created a horrid little jobble on the Black Deep edge. It was dangerous at the time as the wind was still quite light but for its strength it seemed to create a jobble out of proportion.

 

[Yeoman of England]

Dabs

I am just happy that we were able to assist you. We are continually getting upgrades to depth changes, and they will multiply as the various windfarms are constructed.

Regards

Yeoman