Help save Watchet Harbour P L E A S E

[TSB240]

Looks like things are coming to a head.

Oddling Smee's mate has jumped ship.

Drew McDonald, the other director of Watchet Marina resigned from that directorship in the last week, and the directorships of the other marinas, the next week will be interesting for the entire marina group and Watchet.

 

[Concerto]

Sounds like rats leaving a sinking ship.

 

[srm]

Looks as if the marina operator has given up. Just found the "Friendly Marina" website. The latest tide tables and gate times were up to January 2021.

As the petition page said silt removal will be an ongoing operation, even if the harbour was dredged to re-establish the depths. Back in the early 70's my first job after university was as a trainee hydrograhic surveyor with a govt funded research organisation. We spent a lot of time in the Bristol Channel measuring the "fluid mud" loads and distribution for the Port of Avonmouth and the (then) new dock. The bottom few metres on the ebb carried an impressive dense load that obviously settles out anywhere the velocity decreases.

Have signed the petition and hope it helps, though umpteen years since I lived in the area.

 

[Capt Popeye]

Silting up harbours and Rivers , my take is that if these facilities were used more often , agressively , by motor boats , jet Ski etc , just running up n down this action would stir up the light silt and possibly be taken away out of the Harbour

The fact that there is very little movement , certainly NO agressive movement in side these Harbours means that the sediment just settles then become fixed n hard

 

[penfold]

Where does the mud come from? I don't see a river flowing into the harbour, is it solely Severn mud coming in on the tide?

 

[Snoopy463]

Where does the mud come from? I don't see a river flowing into the harbour, is it solely Severn mud coming in on the tide?

Unfortunately yes. Bristol Channel water has been described as being akin to Turkish coffee. When not being stirred, there’s a lot of solids that sink to the bottom.

 

[Praxinoscope]

Board meetings at The Marine Group must be interesting now with Mr Odling-Smee perhaps feeling a bit lonely, Companies House shows that he remains as the only board member after Drew Mcdonald and Kerry Mcdonald both resigned on 31st March 2023.

 

[Praxinoscope]

Where does the mud come from? I don't see a river flowing into the harbour, is it solely Severn mud coming in on the tide?

The lack of a river flowing through the harbours is part of the problem in that there is nothing to assist scouring of the harbour on the ebb.

 

[penfold]

Wouldn't a lock, a header tank and a rudimentary clarification system be enough to keep most of the mud out? Costly, but a lot cheaper than endless dredging.

 

[Praxinoscope]

Wouldn't a lock, a header tank and a rudimentary clarification system be enough to keep most of the mud out? Costly, but a lot cheaper than endless dredging.

I think something greater than a header tank would be needed, there is IMHO no real alternative to either a river flowing through a harbour to act as a scouring agent or in the case of Watchet and Burry Port that have no river, regular dredging but first the current accumulation of silt has to be removed which is the initial major cost after which regular water injection dredging may be sufficient.

 

[AntarcticPilot]

The lack of a river flowing through the harbours is part of the problem in that there is nothing to assist scouring of the harbour on the ebb.

There is a system that can be implemented is if there is an inner harbour that can be fitted with sluice gates. The gates are closed on a high tide, and then the water is released at low water to scour the outer harbour. A system like this is in place at St Andrew's harbour to keep the harbour entrance clear. You don't do it every tide, just as and when necessary. But I don't think it would remove large quantities of silt. It also requires suitable training walls in the area to be scoured.

The other point is that sediment movement mainly happens during extreme conditions, and is mostly what is called "bed load" - that is, it isn't suspended particles, but semi-fluid mud at the bottom. So there will be occasional major sedimentation episodes corresponding to Spring tides or extreme weather conditions, followed by static conditions for most of the time. The load-carrying capacity of a flow of water increases as some power of the velocity; I forget the exponent exactly, but it's at least as the velocity squared and I think it's actually a higher power - cubed or to the fourth power. So the ability to carry sediment increases VERY rapidly as the speed of the current increases - at the very least, 4 times as much for a doubling of the current speed, and probably more like 8 or 16 times. So you can get the harbour nicely cleared and then have all your good work overcome during one big tide.

I'm afraid that a harbour like Watchett (and I do know it slightly; my aunt lived at Minehead, so I have visited Watchett, by land) can only be maintained by fairly heroic engineering or dredging initiatives. Without a clear commercial incentive, such things aren't going to happen - and leisure boating isn't likely to provide a sufficient incentive, especially as it requires substantial investment BEFORE any income can accrue. If Watchett provided floating berths for hundreds of yachts paying several thousand pounds each per year (I am comparing with marina fees on the East Coast at marinas requiring regular dredging) it might be viable, but I gather that a) it hasn't that kind of capacity and b) there isn't a demand for marina type berths in that area.

 

[Praxinoscope]

AntarcticPilot makes some good points in #31, unfortunately with no 'inner harbour' at Watchet to provide the sluicing effect it must I think rely upon regular dredging to keep it clear of silt, and as AP says this is expensive and potentially uneconomical.
Burry Port might just be able to adopt such a sluice gate ystem as there are the remnants of an inner harbour there, but this agan would need heavy investment with potentially little financial profit.

 

[MisterBaxter]

I think I'd personally prefer a cheaper trot mooring in a well run drying harbour to an expensive pontoon mooring in a badly run marina. If others felt the same, that might give a clue as to a workable future for Watchet.

 

[Praxinoscope]

I think I'd personally prefer a cheaper trot mooring in a well run drying harbour to an expensive pontoon mooring in a badly run marina. If others felt the same, that might give a clue as to a workable future for Watchet.

I have occasionally wondered if Watchet was suitable for trots, (I agree on expensive pontoons, I'm completely happy rowing out to my mooring in Abeaeron,) but Watchet still needs to be fully dredged no matter what form of mooring is adopted and will also need regular dredging.

 

[AntarcticPilot]

I think I'd personally prefer a cheaper trot mooring in a well run drying harbour to an expensive pontoon mooring in a badly run marina. If others felt the same, that might give a clue as to a workable future for Watchet.

But of course, that restricts the clientele to boats capable of taking the ground. My fin keeler would not be happy in a drying harbour!

 

[Snoopy463]

But of course, that restricts the clientele to boats capable of taking the ground. My fin keeler would not be happy in a drying harbour!

I’m quite happy using Watchet the way it is. My fin keeler is happy to sit to its waterline in nice soft mud, as indeed it does on its home mooring. I guess large mobies tend not to like sitting in mud, intakes blocking and blue underwater lights not visible?

 

[penfold]

I think something greater than a header tank would be needed, there is IMHO no real alternative to either a river flowing through a harbour to act as a scouring agent or in the case of Watchet and Burry Port that have no river, regular dredging but first the current accumulation of silt has to be removed which is the initial major cost after which regular water injection dredging may be sufficient.

I mean a header tank as a receiver for water pumped out of the lock rather than simply letting it out into the estuary from a sluice; as the water is clean-ish and that cleanliness has been acquired at some effort.

 

[Seastoke]

I’m quite happy using Watchet the way it is. My fin keeler is happy to sit to its waterline in nice soft mud, as indeed it does on its home mooring. I guess large mobies tend not to like sitting in mud, intakes blocking and blue underwater lights not visible?

That’s a very stupid pun in a serious matter.

 

[PCUK]

That’s a very stupid pun in a serious matter.

Easy Tiger!

 

[TSB240]

It seems the contract dredging carried out by the Marine Group at Deganwy Marina has been found to be next to useless.

The common factor in all these marinas is a lack of good flow of water through them.
All that the puny Water Injection Dredgers do is stir up the light sediments to allow it to block up the gate mechanisms or redistribute to settle as another mud bank mostly under existing pontoons and fingers.

The only effective dredging locally was carried out by a Dutch crew with a cutter suction dredger and associated floating pipe disposal into either a fast running ebb tide or a "Stilling Lagoon"

Watchet and Burry port look like gigantic stilling lagoons. The 5 years of neglect by the Marine group mean that only excavation or cutter suction dredge is the only long term solution.

Our local council run marinas have both been excavated this way. Both are at or near full occupancy and have long waiting lists. 8 years ago it was a different story. Both were in dire need of dredging and occupancy was low.

The traditional contents of a stilling lagoon were usually highly valued by the agricultural community as fertilizer but not now if full of antifouling toxins.