Jump to content

Yikes! Land Locked


Midnight

Featured Posts

15 hours ago, dmr said:

The culvert just outside Liverpool took a while to fix and the Mytholmroyd hole looks potentially difficult as the access is not good and the land is quite high and steep.

 

I think some repairs get done quickly by the local CRT team with a few sandbags and a bit of puddling clay, and if its more complicated then it involves designs, permissions and takes forever.

 

There was a very similar failure here a few years ago which was quite quickly fixed. Of course it may be that repair that has now failed.

I wonder whether the Figure of Three works mean this will be a priority to maintain access to the Upper C&H (particularly for boats that can't use the HNC), or whether repairs to Fo3 will suck up all the resources.

Link to comment
Share on other sites

Flooding could have been avoided,or at least significantly reduced if rivers had been regularly dredged.

I know the pathetic excuses trotted out by CRT and th EA,  "difficult to dispose of the spoil " because it has to be tested for nasties and disposed of environmentally.

How about saying stuff the regs,and just put the dredgings on the bank.It will save the cost of disposal and increase the riverbank height.

There is an argument put about by some that dredging is ineffective.I think that is rubbish.

Get a length of drainpipe,pour a bucket of water down it and measure the flow.

Put your hand over half of the end and pour another bucketfull down and see if the flow increases.

The argument that it is too expensive doesn't hold water.(sorry about that one)

because the cost of the damage done to housing,roads,railways,and dare I say it,canal infrastructure I would guess will exceed the cost of dredging.

If the government can spend a hugh wad on a questionable railway, then I am sure they can spare a bit to pay for dredging.

Link to comment
Share on other sites

I wouldn't have thought dredging would have significant impact on flood prevention. You're dredging a narrow channel, so you'd have to do it bloody deep to impact the volume that's been flowing against the defenses / outer banks lately

Link to comment
Share on other sites

5 minutes ago, sirweste said:

I wouldn't have thought dredging would have significant impact on flood prevention. You're dredging a narrow channel, so you'd have to do it bloody deep to impact the volume that's been flowing against the defenses / outer banks lately

 

Dredging does NOT work.

 

A presentation by the agency, called To Dredge or Not to Dredge?, spells out the problems in terms that even ministers can understand: "The river channel is not large enough to contain extreme floods, even after dredging. Dredging of river channels does not prevent flooding during extreme river flows … The concept of dredging to prevent extreme flooding is equivalent to trying to squeeze the volume of water held by a floodplain within the volume of water held in the river channel. Since the floodplain volume is usually many times larger than the channel volume, the concept becomes a major engineering project and a major environmental change."

Is that not bleeding obvious? A river's capacity is tiny by comparison to the catchment from which it draws its water. You can increase the flow of a river by dredging, but that is likely to cause faster and more dangerous floods downstream when the water hits the nearest urban bridge (something the residents of towns like Taunton and Bridgwater should be worried about). If you cut it off from its floodplain by turning it into a deep trench, you might raise its capacity from, say, 2% of the water moving through the catchment to 4%. You will have solved nothing while creating a host of new problems.

Among these problems, the Environment Agency points out, are:

1. Massive expense. Once you have started dredging, "it must be repeated after every extreme flood, as the river silts up again".

2. More dangerous rivers: "Removing river bank vegetation such as trees and shrubs decreases bank stability and increases erosion and siltation."

3. The destabilisation of bridges, weirs, culverts and river walls, whose foundations are undermined by deepening the channel: "If the river channels are dredged and structures are not realigned, 'Pinch Points' at structures would occur. This would increase the risk of flooding at the structure." That means more expense and more danger.

4. Destruction of the natural world: "Removing gravel from river beds by dredging leads to the loss of spawning grounds for fish, and can cause loss of some species. Removing river bank soils disturbs the habitat of river bank fauna such as otters and water voles."

As the agency says, dredging is primarily a tool for improving navigation and, in some places, land drainage. It has been mistaken by people who ought to know better, including ministers, as a means of dealing with a different problem: flooding.

If you want to stop rivers from ruining people's lives, you should engage with the kind of issues that Paterson hinted at. That means, broadly speaking, the following:

More trees and bogs in the uplands – reconnecting rivers with their floodplains in places where it is safe to flood (and paying farmers to store water on their fields while the danger passes);

Making those floodplains rougher by planting trees and other deep vegetation to help hold back the water – lowering the banks and de-canalising the upper reaches, allowing rivers once more to create meanders and braids and oxbow lakes. These trap the load they carry and sap much of their destructive energy.

None of these produce instant results. But they are distinguished from dredging in one significant respect: they work.

 

https://www.theguardian.com/commentisfree/2014/jan/30/dredging-rivers-floods-somerset-levels-david-cameron-farmers

 

 

 

It is simply not practical to contemplate dredging of the    channel    (let    alone    the    floodplain)    to    the    extent    that    would    be    required    to    confine    such    large    and    rare    flood    flows    from    the    wider    floodplain,    since    the    storage    and    conveyance capacity of the channel is a small fraction of    that    of    the    wider    floodplain.    In    this    respect,    dredging    cannot    prevent    flooding.

https://www.ciwem.org/assets/pdf/Policy/Reports/Floods-and-Dredging-a-reality-check.pdf

  • Greenie 2
Link to comment
Share on other sites

On 18/02/2020 at 16:12, cuthound said:

When the Blisworth Tunnel suffered a roof fall in 1980, the repairs took 4 years.

 

During that time there was no alternative north/south route available except on the back of a truck.

 

Excellent article documenting the repairs on the Fulbourne site.

 

http://www.fulbourne.org.uk/index.php/miscellaneous/blisworth-tunel-reconstruction-1980-s

Er, via the GU north to Braunston, Oxford and Thames then GU south via Brentford?

Link to comment
Share on other sites

16 hours ago, Alan de Enfield said:

 

Dredging does NOT work.

 

A presentation by the agency, called To Dredge or Not to Dredge?, spells out the problems in terms that even ministers can understand: "The river channel is not large enough to contain extreme floods, even after dredging. Dredging of river channels does not prevent flooding during extreme river flows … The concept of dredging to prevent extreme flooding is equivalent to trying to squeeze the volume of water held by a floodplain within the volume of water held in the river channel. Since the floodplain volume is usually many times larger than the channel volume, the concept becomes a major engineering project and a major environmental change."

Is that not bleeding obvious? A river's capacity is tiny by comparison to the catchment from which it draws its water. You can increase the flow of a river by dredging, but that is likely to cause faster and more dangerous floods downstream when the water hits the nearest urban bridge (something the residents of towns like Taunton and Bridgwater should be worried about). If you cut it off from its floodplain by turning it into a deep trench, you might raise its capacity from, say, 2% of the water moving through the catchment to 4%. You will have solved nothing while creating a host of new problems.

Among these problems, the Environment Agency points out, are:

1. Massive expense. Once you have started dredging, "it must be repeated after every extreme flood, as the river silts up again".

2. More dangerous rivers: "Removing river bank vegetation such as trees and shrubs decreases bank stability and increases erosion and siltation."

3. The destabilisation of bridges, weirs, culverts and river walls, whose foundations are undermined by deepening the channel: "If the river channels are dredged and structures are not realigned, 'Pinch Points' at structures would occur. This would increase the risk of flooding at the structure." That means more expense and more danger.

4. Destruction of the natural world: "Removing gravel from river beds by dredging leads to the loss of spawning grounds for fish, and can cause loss of some species. Removing river bank soils disturbs the habitat of river bank fauna such as otters and water voles."

As the agency says, dredging is primarily a tool for improving navigation and, in some places, land drainage. It has been mistaken by people who ought to know better, including ministers, as a means of dealing with a different problem: flooding.

If you want to stop rivers from ruining people's lives, you should engage with the kind of issues that Paterson hinted at. That means, broadly speaking, the following:

More trees and bogs in the uplands – reconnecting rivers with their floodplains in places where it is safe to flood (and paying farmers to store water on their fields while the danger passes);

Making those floodplains rougher by planting trees and other deep vegetation to help hold back the water – lowering the banks and de-canalising the upper reaches, allowing rivers once more to create meanders and braids and oxbow lakes. These trap the load they carry and sap much of their destructive energy.

None of these produce instant results. But they are distinguished from dredging in one significant respect: they work.

 

https://www.theguardian.com/commentisfree/2014/jan/30/dredging-rivers-floods-somerset-levels-david-cameron-farmers

 

 

 

It is simply not practical to contemplate dredging of the    channel    (let    alone    the    floodplain)    to    the    extent    that    would    be    required    to    confine    such    large    and    rare    flood    flows    from    the    wider    floodplain,    since    the    storage    and    conveyance capacity of the channel is a small fraction of    that    of    the    wider    floodplain.    In    this    respect,    dredging    cannot    prevent    flooding.

https://www.ciwem.org/assets/pdf/Policy/Reports/Floods-and-Dredging-a-reality-check.pdf

Well said - it seems that it needs stating all too often as the contrary myth keeps on re-surfacing, especially amongst hose who do not want to have to stump up for the more effective solution. Guess what the difference is between them? One is paid for by the landowners and one is paid for by the rest of us.

 

Evidence based policies?

  • Greenie 2
Link to comment
Share on other sites

I think in this case dredging would have achieved very little. Figure of Three locks are so named because the adjacent River Calder winds past the locks on a path resembling the figure 3.  Where it meets the river bank of the final loop is at an acute angle and just yards away from the towpath which gets washed away regularly. CaRT have been fighting a continuous battle, using dolomite and rubble to refill the scouring each time. The flood of February 9 reached new record heights in the vicinity and clearly washed out a huge portion of river bank allowing the raging flood to get across to the non-towpath side of the locks and scour away the by-washes.  Not easy to think of a long term solution and it's possible the work required to either straighten out the river or build a resilient wash wall would not be CaRT's responsibility.

Link to comment
Share on other sites

Any dredging against flooding on rivers with locks is utterly pointless.  The surface level of the water is determined by the next lock down.  All that dredging will do is make the river deeper when it isn't in flood.  Additional level rises following heavy rain will produce the exact same outcome whether dredging has been done or not.

 

Yet I've seen a few tv news programmes this week, talking to landowners along rivers who are insisting that their land is flooding due to lack of dredging. At no point has an expert been there to challenge them and the reporter hasn't challenged this nonsense either.  The result is that the public think it's a dredging issue rather than a land management and climate change issue.

Edited by doratheexplorer
Link to comment
Share on other sites

On 18/02/2020 at 20:49, AndrewIC said:

Is there any more information on the nature of the damage at Figure of Three Locks?

The River breached the retaining wall, nature decided it wanted to go straight and not round a corner.

It smashed the offside wall and lock landing and this is what has ended up in the canal, a massive mound of bricks and debris.

So the bywash has effectively become the canal.

Link to comment
Share on other sites

An example of the estate owners not doing what they should to (among other things) protect people from flooding. Their insistence on burning simply to keep a 'sport' of shooting birds alive and 'well stocked' is maddening in this day n age

 

https://www.theguardian.com/environment/2020/feb/20/grouse-moors-owners-threaten-government-with-legal-action

I imagine they are pleased that Joe public thinks dredging will help so that there's no attention on them

  • Greenie 4
Link to comment
Share on other sites

4 hours ago, sirweste said:

An example of the estate owners not doing what they should to (among other things) protect people from flooding. Their insistence on burning simply to keep a 'sport' of shooting birds alive and 'well stocked' is maddening in this day n age

 

https://www.theguardian.com/environment/2020/feb/20/grouse-moors-owners-threaten-government-with-legal-action

I imagine they are pleased that Joe public thinks dredging will help so that there's no attention on them

It's not the burning of heather that's the problem it's the ripping out of trees, hedges and shrubs, the construction of drainage channels creating access roads for all shooting party vehicles and clearing tributaries of willows and sedges. That's what contributes to the rapid rise in levels lower down the river systems. I live in the moors and when burning takes place, it is in small patches just a small proportion of the moorland.

 

Somebody in authority, please join the dots up.

Link to comment
Share on other sites

Well, burning heather certainly isn't part of the solution, but yes I take your point that the loss of tree's is worse. Still they ain't going to plant woods / forests on their estates if they won't even stop burning heather for 'the greater good'

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.