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R Thames flood scheme
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R Thames flood scheme

Today, I attended a Consultation Event in Chertsey.

The position is that we will be affected by the Spelthorne Channel Section. This will exit the Thames upstream from Chertsey Lock and flow into Littleton North Pit (the one the other side of Littleton Lane from Ellis). The flow will be controlled by a large radial gate (or gates) with a fish pass – now a legal requirement on all control structures. From Littleton North it will flow into Ellis via a culvert under Littleton Lane and then into Big Sheepwalk via a channel cut into the causeway. It will exit Big Sheepwalk into a newly dug channel with a fixed crest weir, again with a fish pass, about 500 yards downstream from the exit. From there it will eventually return to the Thames upstream from the Desborough Cut. There will be a sweetening flow at all times down the channel, provided by water cascading over the (normally shut) radial gate, of 0.5 cumecs. I was surprised how low this is, by contrast the Jubilee River has a sweetening flow of 5 cumecs. (A cumec is a cubic metre per second, as a unit of rate of flow of water).

The channel will be operated in conjunction with Thames weirs, the EA will not wait until Thames weirs are fully drawn before using the channel – they tried that the first time they used the Jubilee River and flooded Wraysbury. The sequence will be, I think, – open some gates on Thames weirs, then put some water down the channel, open more Thames weir gates, more down the channel and so on.

How will this affect us? Littleton North, Ellis and Big Sheepwalk will be interconnected, allowing fish movement. The only way to preserve the status quo would be to have gates on the culvert and channel, which I simply cannot see the EA doing – cost, complications in operation etc. I would be very surprised, if, in normal conditions fish took advantage of the fish passes to leg it into the Thames, and I cannot see them swimming through an open weir gate to escape upstream or escaping over the fixed crest weir downstream. I can, however, see fish coming in from the Thames when the upstream gate is open. Good or bad, I don’t know – we’ll find out. I can’t really picture fish being washed away downstream; the fixed crest weir would prevent that.

Following COVID things are starting to wake up and the EA will be taking soil samples from the lake bed via a pontoon in Ellis in the very near future and in Big Sheepwalk (from which we may get a bigger car park, they need quite a big compound) after that.

There may, of course, be fishing rights available on the new channel downstream of Big Sheepwalk.

I don’t think that there’s any question of Ellis becoming public access.

The timetable is for work to begin in 2026 and completion in 2030.

One more thing, at one of the public meetings Grant was approached by one of the canoeists’ representatives, who gleefully told him that the Thames Conservancy Act gave a legal right of navigation into any water connected to the Thames, so that canoeists would have unrestricted access to Ellis etc. I raised this today and this is not the case, any such access would have to be negotiated and anyway, physical barriers will be in place and there will be minimal headroom in the culvert.

I hope this post has been useful.

Ian Campbell

Thames Flood Scheme

Posted 07/12/22