Whaley Bridge Evacuated

[eggsarascal]

16 hours ago, Chalgravesteve said:

I'm sure that there are additional overflows etc that would have come into play.

 

I don't know the area or the canal/river network, or the background of CaRT. It is true to say, in my view, that there have been a number of organisations that have adopted a "charity status" to oversee the management of previously public owned facilities, which gives them a massive taxation advantage that they didn't previously enjoy as a "normal" organisation. In many cases, the board/exec officers are very handsomely paid, so the setting up of a "management team" to take over of the running of an organisation that they can't afford to buy but then don't have to, and then voting themselves much higher salaries out of the new surplus from the lower tax regime! Very little overview on this.

 

With regards to actual reservoirs though, there are stringent regulations (as you might think) in the maintenance and inspections of these. My main business is a golf club and in 2009 we constructed a small reservoir to store water for irrigation purposes. Originally, the reservoir was designed to hold around 15,000m3 of water. As a result of proposed changes to the Reservoirs Act, we reduced that to just under 10,000m3 capacity, as anything above 10,000m3 was then going to require annual inspections and testing by independent third parties. This was going to be ridiculously expensive for a small reservoir.

 

There are two types of reservoir, non impounding and impounding. Mine is a non impounding, which means that there are no water sources that feed directly into the reservoir, and all the edge slopes away from the top bund slope away from the edge, so that there can be no water run off from rainfall. The only way my reservoir can fill, is from rainfall actually landing on the surface, or me pumping water into it from an abstraction source.

 

The Toddbrook reservoir is an impounding reservoir. It is filled from river that enters the north/western end, which in turn collects run off water from the surrounding area. So its rather like a tap, except that a tap normally has a maximum amount of water that can pass through it. The surface area of the Toddbrook reservoir is about 100,000m2 by my rough estimate. The spillway would normally be at least 50cm ABOVE the standard full level, so in order to start flowing, there reservoir has the ability to store an increased amount above its normal holding capacity before it starts to overflow. So for the reservoir to rise by 2m in height, 200,000,000 litres have had to flow into it. It would be really rare as well, in my view, for a reservoir to be at its upper limits in July/August, although if its sole purpose is to be the header tank for the canal network I suppose that that might be possible. 

 

So put this into perspective. Rainfall on the reservoir on its own, cannot do that. If you get massively excessive rainfall, lets say 6" in old money or 150mm, in a few hours or even over a couple of days, what that actually means is that the volume of water that has fallen from the sky, is 150 litres per 1m2 which will raise the level of the reservoir by 150mm, assuming that there is no outflow. This wouldn't even bring it up to the spillway. The ANNUAL average rainfall for the whole of the UK is 885mm. The news reports were talking about getting 1 months rain in a few hours, maybe 4" or 100mm. so the reservoir would only increase in depth by 100m! 

 

Except that, there is an uncontrollable flow entering the reservoir from its impounding river. The river is collecting water like a giant funnel from the surrounding area, massively increasing the catchment and volume and chucking all of that into the reservoir. If the increase was (and clearly it was) sufficient to fill the reservoir "spare overflow" capacity to the point where it overtopped the spillway, then the volumes are really not manageable. The damage would have been caused as the reservoir continued to fill, increasing the steady trickle over the spillway into a raging torrent of several feet depth, with enough water still coming down off the hills to keep pushing it over the top from behind. If you turn off the tap, the bath stops filling immediately! They are pumping out water and dropping the level by 2m every 24 hours. The incoming water raised the reservoir at at least the same sort of rate as that! 

 

Had the Toddbrook reservoir not been there, it would be extremely likely that the areas downstream of where it is now, would have suffered extensive flooding. The reservoir held the excess capacity and it was not until the spillway gave way that there became an issue, at which point you are really in trouble! 

 

So irrespective of the current lack of proper management or the way that it is run by CaRT, the engineers who built it 180 years ago, managed to do so in a manner that dealt with a once in 180 years event and its still standing!  

 

 

 

  

 

 

If I'm reading this correctly you are agreeing the overflows to/from the cut could have been used, (in a controlled manor) also pumps could have been brought in to eliviate the flow before the slipway became overwhelmed?

Edited August 7, 2019 by eggsarascal

[Woodlover]

23 hours ago, Chalgravesteve said:

with a once in 180 years event

Its usually most years a 1 in 100 year event. I see where you are coming from with the 180 but I would also say that the maintenance has maybe not been so bad in 180 years to.

 

How rare is extreme weather that causes flooding.  

2004 Boscastle Cornwall

2005 Flooding in January in Carlisle and June it was the North York Moors

2007 June and July Yorkshire and the Humber and South Midlands

2008 Sept ,south Wales and north-east England, Oct east Devon

2009 November ,The lake District

2010 November , Cornwall

2012 No flooding but November 2012 resulted in one of the wettest weeks in England in the last 50 years

2014 January to mid-February saw widespread impacts and major flooding problems.

2015 North UK and Cumbria

2016 November flooding mainly across parts of south-west England

2018 October, south Wales particularly badly affected by flooding.

 

I know that not all events above were called a 1-100 year event but a lot were .These 1-100 year events or extremes of weather are so common they are to be expected...If I had an old Dam ,at the wettest time of the year and the long range weather forecasts were all unusually agreeing and saying a wet and windy month to come, do you fill it or keep it at a safe level in case of extreme rainfall? 

 

 

 

[difflock]

I was mulling over the likelyhood that because August is probably the busiest month on the canals, a CART manager decided to keep the reservoir water levels high, and was caught out by the weather forecast actually being correct, which would be entirely understandable.

BUT! the self-same manager would have been eviscerated on public media if their had been insufficient water later in August for to allow boaters to use the locks on their canal boat holidays.

The lack of proper inspection(and perhaps invasive or some penetrative inspection was needed simply because of the nature of the construction of this dam and its age) and maintenance of the dam is another issue.

Because the various dam failure modes are well understood, especially after the very publicised slipway failure of that dam in California very recently.

Edited August 7, 2019 by difflock

[eggsarascal]

Why are people talking about 1-180 year events?, that's when the reservoir was constructed, the bit that failed, (the slipway) was constructed in 1969. Not really held up well considering it's only 50 years old.

[Chalgravesteve]

23 hours ago, eggsarascal said:

If I'm reading this correctly you are agreeing the overflows to/from the cut could have been used, (in a controlled manor) also pumps could have been brought in to eliviate the flow before the slipway became overwhelmed?

I saw a YouTube video showing the overflow channel that comes around the side of the reservoir with deep fast flowing water. It was flowing well before the slipway started to discharge (into the same channel). 

 

The channel couldn’t handle the volume of water being thrown into it and areas like a children’s playground were getting flooded. 

 

So there were efforts to divert the inflow to the reservoir before it overtopped the spillway. 

 

 

[Chalgravesteve]

9 hours ago, eggsarascal said:

Why are people talking about 1-180 year events?, that's when the reservoir was constructed, the bit that failed, (the slipway) was constructed in 1969. Not really held up well considering it's only 50 years old.

The reservoir has been there 180 years and this is the first time it’s been breached? That’s once in180 years then 

 

you could argue that without the spillway being constructed 50 years ago, the dam would have overtopped and it would have collapsed. The spillway, despite sustaining damage did its job 

[Chalgravesteve]

On 07/08/2019 at 08:25, Woodlover said:

Its usually most years a 1 in 100 year event. I see where you are coming from with the 180 but I would also say that the maintenance has maybe not been so bad in 180 years to.

 

How rare is extreme weather that causes flooding.  

2004 Boscastle Cornwall

2005 Flooding in January in Carlisle and June it was the North York Moors

2007 June and July Yorkshire and the Humber and South Midlands

2008 Sept ,south Wales and north-east England, Oct east Devon

2009 November ,The lake District

2010 November , Cornwall

2012 No flooding but November 2012 resulted in one of the wettest weeks in England in the last 50 years

2014 January to mid-February saw widespread impacts and major flooding problems.

2015 North UK and Cumbria

2016 November flooding mainly across parts of south-west England

2018 October, south Wales particularly badly affected by flooding.

 

I know that not all events above were called a 1-100 year event but a lot were .These 1-100 year events or extremes of weather are so common they are to be expected...If I had an old Dam ,at the wettest time of the year and the long range weather forecasts were all unusually agreeing and saying a wet and windy month to come, do you fill it or keep it at a safe level in case of extreme rainfall? 

 

 

 

This is exactly their problem. If they dumped 1/3rd of the reservoir capacity every time they had heavy thunderstorms predicted, they would get so much criticism! They were between a rock and a hard place (although if the spillway was there then they wouldn't have had the problem!!) that they need the reservoir full to meet their high level demand, in a period of time not usually associated with torrential and sustained downpours. Its taken them a week with emergency pumps going full blast to lower the level, you simply cannot shift that volume of water in a short time frame, so the likelihood is that they probably needed to start shifting water OUT of the reservoir a week or more ahead, before the bad weather was even forecast!! 

 

And if you search on youtube for the USA spillway destruction, you will see that however good and solid it looks, the destructive power of flowing water is staggering once its found a way into the structure. 

 

Its OK if you are like the Hoover Dam, with huge solid rock formations acting as buttresses to the dam. They bored tunnels through that rock so that they could release water if they needed to. If they open those gates for 24 hours, the only thing that's going to happen to the tunnels is that the rock walls will get a little bit smoother than they were before!

 

I'm not defending in anyway a lack of maintenance (perceived or real - there was a quote from a reservoir panel engineer saying that she couldn't see anything that caused her concern in the pictures taken prior to the problem). 

 

 

[eggsarascal]

11 minutes ago, Chalgravesteve said:

This is exactly their problem. If they dumped 1/3rd of the reservoir capacity every time they had heavy thunderstorms predicted, they would get so much criticism! They were between a rock and a hard place (although if the spillway was there then they wouldn't have had the problem!!) that they need the reservoir full to meet their high level demand, in a period of time not usually associated with torrential and sustained downpours. Its taken them a week with emergency pumps going full blast to lower the level, you simply cannot shift that volume of water in a short time frame, so the likelihood is that they probably needed to start shifting water OUT of the reservoir a week or more ahead, before the bad weather was even forecast!! 

 

And if you search on youtube for the USA spillway destruction, you will see that however good and solid it looks, the destructive power of flowing water is staggering once its found a way into the structure. 

 

Its OK if you are like the Hoover Dam, with huge solid rock formations acting as buttresses to the dam. They bored tunnels through that rock so that they could release water if they needed to. If they open those gates for 24 hours, the only thing that's going to happen to the tunnels is that the rock walls will get a little bit smoother than they were before!

 

I'm not defending in anyway a lack of maintenance (perceived or real - there was a quote from a reservoir panel engineer saying that she couldn't see anything that caused her concern in the pictures taken prior to the problem). 

 

 

The only reason CaRT need to keep the reservoir full is lack of maintenance on the network. I think it was @aspenarb b0D, that was doing some work for a hotel boat that had been put on restricted movements due to lack of water, (handy when someone's trying to run a business, and paying through the teeth for the pleasure), To put it another way, if so much water wasn't lost due to lack of maintenance there would be no need to store that volume of water.

[Chalgravesteve]

6 minutes ago, eggsarascal said:

The only reason CaRT need to keep the reservoir full is lack of maintenance on the network. I think it was @aspenarb b0D, that was doing some work for a hotel boat that had been put on restricted movements due to lack of water, (handy when someone's trying to run a business, and paying through the teeth for the pleasure), To put it another way, if so much water wasn't lost due to lack of maintenance there would be no need to store that volume of water.

Ah I see, the network is pissing water out everywhere so they need lots of water at the top!  

 

They do need to keep the reservoir reasonably full, it would actually probably cause more maintenance issues of the reservoir itself if you allow the upper sections to dry out and become overgrown.  

 

There will always be two sides to a story, its probably far easier for them to keep pushing water into the system than to shut and drain sections (which causes disruptions to others - who will complain vociferously when it directly affects them, but will otherwise just let it pass when it doesn't!), but that becomes necessary when safety is compromised. Modern policy on a lot of infrastructure these days seems to be patch and repair until its so bad it can't be! 

[eggsarascal]

11 minutes ago, Chalgravesteve said:

Ah I see, the network is pissing water out everywhere so they need lots of water at the top!  

 

They do need to keep the reservoir reasonably full, it would actually probably cause more maintenance issues of the reservoir itself if you allow the upper sections to dry out and become overgrown.  

 

There will always be two sides to a story, its probably far easier for them to keep pushing water into the system than to shut and drain sections (which causes disruptions to others - who will complain vociferously when it directly affects them, but will otherwise just let it pass when it doesn't!), but that becomes necessary when safety is compromised. Modern policy on a lot of infrastructure these days seems to be patch and repair until its so bad it can't be! 

That's about the size of it, the reservoir was built when the canal was like the M25, boats all over the place day and night, the water stored was needed. The difference is the cut was vital to business so it was maintained to a high standard. It's now mostly used by pleasure boaters/live aborads so no such maintenance takes place until something like Whaley Bridge happens. I see CaRT are now going to rebuild the whole reservoir not just the slipway. I wonder how they are going to keep the cut open while they do that.