Aire & Calder Breach

[matty40s]

25 minutes ago, The Happy Nomad said:

You do have love Facebook.

 

'Put a boat across it'

 

'Wasnt that fixed before' - links to a completely different breech on a completely different navigatioon.

I can only see the comment I posted, no links or comments. 

[Guest]

4 minutes ago, matty40s said:

I can only see the comment I posted, no links or comments. 

Weird it's a public group and if your are able to post you must have joined....

 

 

[matty40s]

I havntv posted and dont do facebook. You can see single pages as a non user, but cant follow links or see comments.

[Guest]

13 minutes ago, matty40s said:

I can only see the comment I posted, no links or comments. 

I clearly misunderstood this.

[Jerra]

3 hours ago, Pluto said:

Your first observation is certainly correct, but I was describing those growing on canal property, which if allowed to grow out of hand will damage the canal's infrastructure. It was one of the main jobs bankrangers did, ensuring that natural growth did not cause breaches, at the same time making it easier to spot problems.

 

I am old enough to remember the smogs we used to get before motorways were built. The Clean Air Act certainly improved matters, though it has probably been the cause of more tree growth on vulnerable embankments. I can remember a time when the Aire valley side below the canal at Armley were almost completely devoid of growth, and since the Act was passed, it has become covered with trees. They are not on canal property, and are probably not destabilising the sloping valley sides, though trees can cause such problems in some circumstances. We live in a man-made environment which means we have to balance the positive and negative sides of nature. The arguments for and against planting trees alongside canals were considered in depth in the early 18th century when the banks of the Canal du Midi were first lined with plane trees, though I am not old enough to remember that happening. There were similar arguments when canals were built in the late 18th century in this country, and I am not old enough to remember them either. However, I have researched the history, so do have some understanding about the benefits or otherwise of trees near to canals.

Interesting.   How does tree growth lead to breaches?    In general trees seem to stabilise slopes binding soil together.   What do they do which causes breaches?

[Alan de Enfield]

1 minute ago, Jerra said:

Interesting.   How does tree growth lead to breaches?    In general trees seem to stabilise slopes binding soil together.   What do they do which causes breaches?

 

Trees will stabilise embankments until the soil reaches a saturation point following continuous heavy rain, at which time the tree will topple and take the bank with it.

 

How many trees have you seen (or seen photos of) that have toppled into the cut and brought the 'landslide' with them ?

[Jerra]

1 minute ago, Alan de Enfield said:

 

Trees will stabilise embankments until the soil reaches a saturation point following continuous heavy rain, at which time the tree will topple and take the bank with it.

 

How many trees have you seen (or seen photos of) that have toppled into the cut and brought the 'landslide' with them ?

If the soil gets to that stage it will form a mud slide anyway.

[Alan de Enfield]

2 minutes ago, Jerra said:

If the soil gets to that stage it will form a mud slide anyway.

I think it takes the 'top-heavy' weight of the tree to break away before the slide will start.

[Jerra]

1 minute ago, Alan de Enfield said:

I think it takes the 'top-heavy' weight of the tree to break away before the slide will start.

Mud slides have been known to start on banks covered with nothing but grass.   Grass toppling wouldn't start the slide.

[Alan de Enfield]

1 minute ago, Jerra said:

Mud slides have been known to start on banks covered with nothing but grass.   Grass toppling wouldn't start the slide.

Of course mud slides can start 'on their own', but at the point of saturation the ground is still stable enough not to slide, the addional weight/load of the tree toppling because the soggy ground no longer has sufficient support for its roots, starts a mud slide, earlier than would have happened on the area if it did not have a tree(s)

[Jerra]

4 minutes ago, Alan de Enfield said:

Of course mud slides can start 'on their own', but at the point of saturation the ground is still stable enough not to slide, the addional weight/load of the tree toppling because the soggy ground no longer has sufficient support for its roots, starts a mud slide, earlier than would have happened on the area if it did not have a tree(s)

I find this suggestion about lack of support from the roots very strange.   For most species there is more mass of tree below ground than above.   Yes trees blow down when the forces and leverage from the trunk caused by the wind make the roots to snap.   What causes the roots to snap on a tree when in waterlogged ground?

[Alan de Enfield]

27 minutes ago, Jerra said:

What causes the roots to snap on a tree when in waterlogged ground?

They don't snap. the wind blows, the ground has no 'support' (is verging on sloppy) the tree falls over and the 'root ball' tips up with the tree, the whole tree slides down the bank.

 

Think of pulling a mooring pin out of the ground - when the earth is dry it is not easy, when the ground is soft / wet  it just pulls out very easily - there is little friction/resistance.

 

 

This article relates to the USA and is regarding Dams and Levees, but I guess as a canl is 'always in water' it is similar.

 

It is also important to consider the function of the embankment.  Adverse effects created by woody vegetation tend to be more apparent on active storage dams because they generally impound water on a permanent basis whereas levees and flood control dams are typically only loaded for a relatively short period of time during flood conditions.  The permanent reservoir loading at active storage dams creates a much higher likelihood that adverse consequences might occur.  At the same time, the sudden loading of levees and flood control dams during flood conditions can lead to the rapid development of adverse conditions of which the owner was previously unaware, leading to emergency actions at a time when emergency response agencies are generally already stressed.  For these reasons, dam and levee owners should strive to eliminate woody vegetation on and near dams and levees.  Only after careful consideration and consultation with dam and levee safety experts should they consider allowing any woody vegetation to remain.

In conclusion, state and federal dam safety officials and industry experts generally agree that trees and woody vegetation should be eliminated from all water impounding structures. The safety and stability of dams and levees depend on the integrity of the embankments and abutments to withstand the hydraulic loads from the water in reservoirs and rivers.  Evidence has demonstrated that woody vegetation is responsible for compromising the integrity of dams and levees, therefore prompt removal of existing woody vegetation on and near dams and levees, and maintenance of uniform dense grass cover on earthen surfaces, is recommended.  If woody vegetation exists on or around a dam or levee, the owner should consult with their engineer and coordinate with their state dam safety official to determine an appropriate vegetation control plan, as policies differ from state to state. Proper maintenance and monitoring of appropriate vegetation around dams and levees will reduce dam failure risk factors and prolong the life of the structure.

[Jerra]

50 minutes ago, Alan de Enfield said:

They don't snap. the wind blows, the ground has no 'support' (is verging on sloppy) the tree falls over and the 'root ball' tips up with the tree, the whole tree slides down the bank.

 

Think of pulling a mooring pin out of the ground - when the earth is dry it is not easy, when the ground is soft / wet  it just pulls out very easily - there is little friction/resistance.

 

An interesting suggestion but I am afraid for me it doesn't make sense.   The average tree has roots which spread at least as far as the branches and go deep into the ground.   Are you saying you have seen root balls as wide as the trees branches reach and deep as well.  I certainly haven't, I think the largest in diameter root ball I have seen was about 8 foot and that was on a wind blown tree so the roots had snapped.

 

Where is TreeMonkey when you need him.

[Alan de Enfield]

1 minute ago, Jerra said:

 

An interesting suggestion but I am afraid for me it doesn't make sense.   The average tree has roots which spread at least as far as the branches and go deep into the ground.   Are you saying you have seen root balls as wide as the trees branches reach and deep as well.  I certainly haven't, I think the largest in diameter root ball I have seen was about 8 foot and that was on a wind blown tree so the roots had snapped.

 

Where is TreeMonkey when you need him.

 

Different specis of trees have different root structures - some even have not much more than a 'tap-root', and some have some very shallow root systems.

[Captain Pegg]

9 minutes ago, Jerra said:

 

An interesting suggestion but I am afraid for me it doesn't make sense.   The average tree has roots which spread at least as far as the branches and go deep into the ground.   Are you saying you have seen root balls as wide as the trees branches reach and deep as well.  I certainly haven't, I think the largest in diameter root ball I have seen was about 8 foot and that was on a wind blown tree so the roots had snapped.

 

Where is TreeMonkey when you need him.

It is basically correct and I’ve explained the phenomenon more than once on the forum.

 

Well drained and deep homogenous soils promote the growth of strong healthy deep rooted trees which do aid the overall strength of the slope but by and large the conditions that promote healthy tree growth are also conducive to sound earthworks.

 

If the slope has shallow soil overlying something relatively solid and impermeable - like rock or the clay core with which many embankments are constructed - then any trees that are allowed to grow will be shallow rooted and weak. The mechanism for starting failure of the slope is as Alan describes. It’s a very genuine phenomenon from which I’ve experienced some awkward moments first hand.

 

Vegetation growth also masks the obvious signs of distress that an earthworks examiner will look for during inspection.

 

It’s why any organisation looking after earthworks will spend a good proportion of their maintenance and repair budget on vegetation clearance on their identified higher risk slopes.

 

[Allan(nb Albert)]

Environment Agency advice for reservoir owners generally  makes sense for other raised water retaining structures such as embankments. 

 

Quote

 

The ideal embankment dam has a healthy, short (50-150mm) covering of grass on its crest and downstream face, with no trees or other vegetation. This allows problems such as settlement, seepage/leakage, slips or burrowing animal activity to be spotted early on before they become dangerous and expensive to fix.

Vegetation can also cause runoff water to form concentrated flow paths which speeds up the surface erosion in these areas.
 

Problems that trees can cause -

 

• Large top-heavy or unstable trees can be blown over in storms, tearing a large hole in an embankment and making it unstable or prone to overtopping or internal erosion.
• Growing tree roots can puncture the waterproof artificial line, leading to internal erosion.
• Growing tree roots can damage wave protection on the upstream face, leaving it exposed to external erosion from wave action.
• Dead or dying tree roots within an embankment can leave holes which form leakage paths, leading to internal erosion.
• Trees near to structures such as drains and concrete spillways can damage the structures to a point where the have to be replaced.

 

•  

[Allan(nb Albert)]

It is also worth saying that, following Toddbbrook reports, CRT tackled its reservoir vegetation backlog last winter.

[Pluto]

Thanks Alan and Allan for your input and quotes. In contemporary literature, it was suggested that the roots of trees close to a canal could break through the lining of a canal in their search for water, and that would cause leaks. On the Canal du Midi, there were arguments for and against. Those for trees suggested that they would both create shade for the horses and boatmen, as well as reducing evaporation, whilst those against suggested damage caused by roots and excessive demand for water extracted from the canal to supply trees through their roots should they become numerous. The former were successful on the Canal du Midi, where summers are considerably hotter than in England. Here the latter argument prevailed, though I have seen it suggested for the Lancaster Canal that trees were planted on small plots of land isolated by canal construction and purchased by the company to provide timber for canal maintenance.

[Arthur Marshall]

When I bought my last house but three I had to have a tree survey as the Building Soc didn't like the sycamores in the garden. The guy said they were no problem as they just have a tap root straight down, no spreading, just giant weeds like dandelions. It's a myth that tree roots spread to the same width as the branches.

[Guest]

21 minutes ago, Arthur Marshall said:

When I bought my last house but three I had to have a tree survey as the Building Soc didn't like the sycamores in the garden. The guy said they were no problem as they just have a tap root straight down, no spreading, just giant weeds like dandelions. It's a myth that tree roots spread to the same width as the branches.

Depends very much on the tree type.

 

The (now gone) Cherry tree in our front garden had a root system that spread many times wider than the canopy and a tap root that grew around 30 to 40 yards from the tree itself.

 

Hated getting rid of it as the blossom in Spring was fantastic but the potential damage wasnt worth it.

[ditchcrawler]

Where is @tree monkey when needed

[tree monkey]

Simply put, it's complicated,

 

Trees and vegetation can help stabilise slopes but also can compromise slopes, it will to a large degree depend on the composition of the actual structure, think woodsheves cutting for an example of the perfect storm of failure.

 

Tap roots are practically none existent on mature trees and the spread of the root structure depends on the substrate and species of tree, crudely the tree will trace areas of water/nutrients plus reactive support growth based on the needs of the tree to be upright, often the root spread will be much bigger than the crown spread.

 

Most rootplate failures will be due to a comprised root system either abiotic/biotic damage or just extreme weather that pushes the tree beyond its tolerances, wet/waterlogged soil lowers the trees ability to "hang on" because the water acts as a lubricant 

 

I'm sure there's loads of questions I've missed, I will be back later

Edited December 27, 2020 by tree monkey

[tree monkey]

4 hours ago, Pluto said:

Thanks Alan and Allan for your input and quotes. In contemporary literature, it was suggested that the roots of trees close to a canal could break through the lining of a canal in their search for water, and that would cause leaks. On the Canal du Midi, there were arguments for and against. Those for trees suggested that they would both create shade for the horses and boatmen, as well as reducing evaporation, whilst those against suggested damage caused by roots and excessive demand for water extracted from the canal to supply trees through their roots should they become numerous. The former were successful on the Canal du Midi, where summers are considerably hotter than in England. Here the latter argument prevailed, though I have seen it suggested for the Lancaster Canal that trees were planted on small plots of land isolated by canal construction and purchased by the company to provide timber for canal maintenance.

The thing about these questions is there are so many variables that there is never one answer, it's fairly obvious that trees don't generally cause issues in the UK because of how many trees exist alongside the canals and how few problems there appear to be directly related to trees.

 

It's likely the reduction in evaporation is balanced by the uptake by the roots, this is a guess by the way but I would suggest a reasonable one, the balance may change in hotter/dryer countries.

 

Direct damage by roots must happen, in fact there are 3 recently felled trees on my moorings but there doesn't seem to be any obvious water loss, maybe as the roots decay leaks may become obvious or maybe the gaps will self sel in some way.

 

 

[XLD]

4 hours ago, The Happy Nomad said:

 

 

The (now gone) Cherry tree in our front garden had a root system that spread many times wider than the canopy and a tap root that grew around 30 to 40 yards from the tree itself.

 

30 to 40 yards from the tree?
Is that a printing error?

I thought tap roots went down?

[Guest]

8 minutes ago, XLD said:

30 to 40 yards from the tree?
Is that a printing error?

I thought tap roots went down?

You could be correct.

 

We had a massive very thick root wrappped around the side of our house.