Thinking about Watchet Mud

[Luminescent]

Bulldozer and dumper truck it is. (A dumper truck in the middle of watchet...lmfao).

[PCUK]

It's been stated previously that the original harbour, with the stream going through it didn't silt up. I put the following on a previous thread, a plan to use the stream water at the best times during the tidal cycle.

I've read the comment on the other thread, saying the "new" method just made holes. I'm not surprised as the pipe dredgers are normally used on underwater archaeological sites. A good bit of kit for the right job but I can't see much use for it in Watchet.
After visiting the marina many times and reading a number of reports on the mud, I came up with my own suggestion.

The stream that comes down off the moors is tidal at the tide end. If a dam was added to hold the level at high tide, it would give a reservoir large enough to produce a large amount of water to pump into the marina. If pipes with a series of jets were laid on the floor of the marina, the fresh water could be used to agitate the silt so it stayed in suspension whist the gate is open. The following things would need addressing/testing:
1. The dam may need to lift/drop when the stream is in flood. (Having a sump would still provide enough water)
2. The best time, of the tidal cycle, for the pumping/agitation would need to be established.
3. The marina may need to be split into sections, which could be agitated one at a time, if the water supply/pumps are too small.

Many people have said that the harbour didn't silt up when it was fed by the stream. This addresses that, in a controlled way. It may also help to have some compressed air added in certain areas. Care would need to be taken as vessels lose buoyancy it there is too much air in the water!
I have some experience of water jets, in industrial process equipment and they don't penetrate far through standing water. The design of the the jets and the jet arrays would be crucial. The key being to produce turbulence.
The whole testing and design process would be perfect for a university project or someones PhD Thesis.

Allan

You're talking about a scouring basin and they work. Ideal with the stream coming down.

[Allan]

You're talking about a scouring basin and they work. Ideal with the stream coming down.

No I'm not! As I said in a post above, it is not like Porlock, which is a scouring basin. The idea, obviously not stated clearly above is for a system that agitates the marina water to put the silt back in suspension. This should ensure the ebb takes out as much as the flood brings in.
Allan

[PCUK]

Ah, now I understand. There again it could work as both an agitator and a scourer with suitable sluices. Either way I would think it a relatively low cost project.
Ideally, what is needed first of all is a well off benefactor to pay for the bedrock dredge. Surely there is someone with half a million to spare who would like to be remembered for their altruism at Watchet!

[Allan]

Ah, now I understand. There again it could work as both an agitator and a scourer with suitable sluices. Either way I would think it a relatively low cost project.
Ideally, what is needed first of all is a well off benefactor to pay for the bedrock dredge. Surely there is someone with half a million to spare who would like to be remembered for their altruism at Watchet!

The scouring idea is OK but my idea is to reduce the cost and disruption by only needing a pipe to connect the dammed stream to the marina. There would not be any need for sluices into the marina. Scouring would require a much larger flow and, in my opinion, would be unsuitable for such a large area. At Porlock the dammed area, behind the gates, is larger than I'm proposing and the marina is many times the size of the hole at Porlock.
I'm beginning to think my description is not very clear!
Allan