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Groundhog Day Floods


Bill
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Perhaps even cleaning & removing debris from the various watercourses would be a start then ,instead of just dredging , see what could be done about making all the watercourses  ,say, a yard deeper than their present river beds.  Shouldn't all this river improvement be possible now we are free from Brussels ?

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That's part of the problem Dave;  speeding up flows in water courses increases the likely hood of flash flooding, especially when combined with high tides.  Whilst we benefit locally from a massive storm drain with the MSC;  it still doesn't stop flooding.   There needs to be areas of soak away, which acting like a sponge to hold the excess water, these can be wooded with Yew to soak up the water.   Higher upstream there needs to be more reservoirs, with hydro-electric dams to capture all this excess energy.  Then we have the problem of the Summer draughts,  more storage, with national distribution canal networks, would help avoid the annual sprinkler bans.    :rolleyes:

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14 minutes ago, Observer II said:

That's part of the problem Dave;  speeding up flows in water courses increases the likely hood of flash flooding, especially when combined with high tides.  Whilst we benefit locally from a massive storm drain with the MSC;  it still doesn't stop flooding.   There needs to be areas of soak away, which acting like a sponge to hold the excess water, these can be wooded with Yew to soak up the water.   Higher upstream there needs to be more reservoirs, with hydro-electric dams to capture all this excess energy.  Then we have the problem of the Summer draughts,  more storage, with national distribution canal networks, would help avoid the annual sprinkler bans.    :rolleyes:

I would suggest it needs to be slow flow where the storage areas are such as north of Winwick Quay but where it passes through built up areas it needs to be fast flowing. That would have ensured that the build up of depth which affected Dallam would not have happened. We need end to end management including sufficient storage to cope with high tide without overtopping the defences. WBC are supposed to do root cause analysis of every flooding event but I haven't seen any recently. Their attempts to fix Densham Avenue were predicated on pushing the water into the very part of the Brook that over-flowed because it couldn't get into the Mersey fast enough. By the time in gets to Higham Avenue slowing the flow causes a flood. They record height but not flow rate as far as I can tell, If anyone knows more tell us please.

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I’d go along with that because a whole lot of this water is domestic run off from St Helens and Newton le Willows which unlike farmland, gets into the brook as fast as the rain comes. Dredging would increase the speed that the water comes down, only to be backed up by a tidal river and end up flooding the lower reaches as we have seen. In any case, it would only end up silting up again and so need constant dredging which is expensive.

Looking on Google, there is plenty of farm and wasteland as Con says just north of Winwick that could be used to create a natural defence to slow the flow and keep it just below flood levels. Another thought might be to reuse the Sankey Canal in much the same way we do with the ship canal. If it fills from upstream, then just open the gates and allow it to become a storm drain when needed, although I doubt the frogs would like that.

 

Bill 😊

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Bill, you do know that the Sankey Canal doesn't exist between Bewsey and Newton Le Willows, it's long been filled in and it would be a major feat of digging to re-instate it?

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That ok Asp, we’ll get you a new shovel.

There is a lot of space up that way that seems to be just wasteland that with a bit of imagination could be transformed into a local water park or nature reserve that doubles as flood prevention. One potential location that caught my eye was the remnants of the canal just below Wargrave. Find this on Google maps then change to satellite view to see that it still contains water and connected to Sankey Brook. This and the surrounding wasteland could easily be further excavated into one large or several small overflow lakes.

The thing is with flood prevention measures, they can be costly and for the odd time they're called upon to do their job, nothing happens so their never fully appreciated. At least with natural solution like this, we get the protection and the benefit of a community asset that can be appreciated every day of the year. It’s sort of two birds with one stone.

.  

Bill 😊

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Another thought about the possibility of using the existing canal might be to re-join the brook to the canal at its present to endpoint as it’s only separated by about 50 metres, so no major expensive work needed. Assuming the level of the canal at this point is lower than the brook in flood, this would provide an alternate escape path for the water and possibly prevent flooding in the Sankey Bridges area. There are no locks along that stretch that I can see although it’d need clearing in places and a dozen pleasure craft might need to find a new home.

Taking this idea further, rather than allowing the canal to drain out at the locks near the Ferry Tavern, if we could use the full length of the canal exiting at Widnes, then we’d have a ten-kilometre-long overflow capable of taking on all the excess water in much the same way as the ship canal does now. The lower reaches would need a lot of clearing and a few more pleasure boats might need to move but it all looks possible and again we’d be creating a pleasant environment that people could enjoy.

As for the dynamics of this well I’m no expert but I’d have thought that giving the flow an alternate route at the current canal endpoint would have the effect of lowering the levels at that point and thus allowing for a significantly faster flow upstream which in turn might reduce the problems at Hawley’s Lane. I’ve no doubt that this idea together with some upstream measures could provide a solution able to deal with anything global warming might throw at us, and if it doesn’t, then at least we’ll have a better environment and a whole lifetime to build better flood defences.

 

Bill 😊

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That sounds a bit double Dutch to me Davy, but I suppose anything’s possible with the council. Canals like this aren’t normally very deep, even the Bridgewater that’s still in use is only about four foot deep in most places but it wouldn’t surprise me though if the St Helens canal is much more than a foot or so deep these days through lack of use and gradual silting.

Obs, Don’t worry you head too much about erosion and sea level increases because there’s a whole lifetime to sort that out whereas another flood like we had a few days ago could happen again tomorrow. As for the need to adapt, isn't that exactly what I was saying in my previous post?

 

Bill 😊

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1 hour ago, Davy51 said:

Didn't WBC reduce the depth of the canal in some parts so it actually hold less water as a drain than it used to ?

There's a small weir on the south side of the canal just off Liverpool Road, so that's the level of the canal  all the way to Spike Island.

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I see. Is there still a sluice at Sankey Bridges into the Mersey?  Even the allowable water level being another couple of foot deeper would possibly help in storing flood water though.

There isn't a lot of length left in the canal these days Bill. There is a stretch in St Helens ,a short length in Haydock ,a  short fishing pound near Penkford school ,then a final length of about a mile from Bradleigh lock to i think it's called Winwick lock , which is just near the low bridge just south of Vulcan Village. I don't think there is any in water canal from there to Dallam.

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If there is it must be well hidden. Just looking on the maps, the Mersey does seem to have a connection to the ship canal at Walton lock although I don’t know if any water flows that way these days.

Bill 😊

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5 hours ago, Bill said:

If there is it must be well hidden. Just looking on the maps, the Mersey does seem to have a connection to the ship canal at Walton lock although I don’t know if any water flows that way these days.

Bill 😊

Bill, there is a rather accurate set of digital map date from the Ordnance Survey called Open Rivers. It shows that there is a source of water approximately 40m West of the basin on the Ship Canal between Landseer Avenue and Waters Edge. You have to superimpose the Open rivers data on a Street View map or equivalent to gat the location data. From that source it flows West into the Mersey. There is no connection between the MSC and the Mersey around that point any more. The is no evidence that the pipe Obs refers to is part of of the waterway on the maps.

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That's exactly what I was talking about, it's visible with the standard Google maps but even if that could be converted to some kind of sluice, I doubt it would have been able to prevent the recent flooding. I did see something about some mega storm drain in the area that empties out into the ship canal and referred to by drain enthusiast as “The Bunker” There’s loads of photos showing huge constructions but nothing to suggest where abouts this is.

https://www.28dayslater.co.uk/threads/bunker-storm-drain-warrington-december-2013.86119/

 

Bill 😊

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The drains are always going to be worked on for maintenance and for increased demand. The number of times we flush the toilet is a known quantity so the foul drains can be planned and sized accordingly but when it comes to rainwater it’s a bit of a guess as to what we might expect in the next hundred years. Even if someone doesn’t believe in global warming, they can’t deny that fact that the number of record-breaking levels are on the increase and each time rivers reach these levels, the entire surface drainage system is more likely to fail.

When I was building my house extension a couple of years back, I was a bit miffed that I couldn’t simply allow rain water to go down the grid along with the sink water and that I had to half kill myself digging a soakaway pit at the far end of the garden. Now having seen the effects of a good deluge I can appreciate why this was necessary. Better to have the grids backing up than the sewers.

 

Bill 😊

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2 hours ago, Evil Sid said:

what was the work united utilities carried out a while back near to morrisons?

I thought that was to help drainage. then again i have had a few sleeps since then so my memory might be dodgy on that score.

I seem to remember they were replacing or repairing a pipe that runs under the canal, but then again I also have had a few snoozes since. 😴

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It rained overnight, not heavy and not from any named storm or anything but just look how fast the brook levels jump when rain like this falls on already saturated ground.

https://flood-warning-information.service.gov.uk/station/5031

Looking at the weather radar it looks like it’s going to clear up soon for a while at least, but it wouldn’t surprise me if we saw a bit more flooding.

 

Bill 😊

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Well it could be argued if you surround a river with flood defences to stop it overflowing, the water level in the river is bound to rise even higher. I don’t think that was the case last week though but simply the sheer volume of water that came down.

My hat’s off to the environmental agency though for predicting todays near miss.  According to the timestamp on www news, they announced this at 10pm last night and I'm not sure if it was even raining at that time. They missed the peak time by a couple of hours but still, their crystal ball must be better than mine.

 

Bill 😊

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I have seen sankey brook flowing backwards once. it was probably due to the tide coming in at liverpool. water level at the time was a few inches and at first i thought i was imagining it until i noticed a few sticks going up stream.

So i guess that they have to factor in how long it takes for the tide to stop up the flow and back the water up to over flowing to get an idea of what time is optimum for flooding. or pull numbers out of a hat and the nearest half hour wins the pot.

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They’ll have some cleaver tech at their disposal Sid because looking at this graph for 10pm the other night, how could they have known we’d hit the flooding point at 10 am the following day when at that time the chart wasn’t even rising?

https://flood-warning-information.service.gov.uk/station/5031

The Causey Bridge monitoring point is up over the other side of the M62 so well out of reach for the Mersey tides and it shows just how fast the brook can reach flood levels when the ground is already saturated.

 

Bill 😊

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