Ratcliffe Lock - River Soar

[Richard T]

We were boating on home territory on Monday and went through Ratcliffe lock. We were pleasantly surprised to see that Land and Water had dredged on behalf of CRT the large shoal that had built up during floods over the past years. Speaking to one of the guys doing the job he said that about 600tonnes of silt has been removed. This has been used to build a berm about 1m high with a crown of about 5m. The down side is that future floods will wash the silt back into the cut. The berm will be eroded from both sides. It would have been better if the berm had been started a metre back from the cut edge.

[matty40s]

......or it will force the water towards the old.lock site, taking silt with it, and blocking the lower lock access with new sand banks.

 

Not that us lot know anything about the rivers of course.

[GRLMK38]

Great to see the work being completed.  The shoal certainly took me by surprise when I tried to move across towards the lock landing.

[matty40s]

1 hour ago, GRLMK38 said:

Great to see the work being completed.  The shoal certainly took me by surprise when I tried to move across towards the lock landing.

The point of the OP being all that will end up back in the cut as soon as it floods again.

Dredging is about removing , not just lifting it out back onto the flood plain it came from.

[GRLMK38]

7 hours ago, matty40s said:

The point of the OP being all that will end up back in the cut as soon as it floods again.

Dredging is about removing , not just lifting it out back onto the flood plain it came from.

The OP was stating an opinion and he may well be qualified to do so, I was merely stating fact (as a boater that reported the issue to C&RT East Midlands Ops in June) because I am not qualified to comment on dredging and reinstatement work on flood plain land.

 

Now with the benefit of hindsight perhaps the OP (or you) could write to the Land and Water and the C&RT Project Manager to explain how they should have done it?

[Momac]

7 hours ago, matty40s said:

The point of the OP being all that will end up back in the cut as soon as it floods again.

Dredging is about removing , not just lifting it out back onto the flood plain it came from.

On the Trent at Stoke Bardolph  they have dredged a channel and deposited the material in the middle of the river .

I guess it has ensured future work as the almost inevitable flooding to come may well put it back where it was.

At least they have done something even if it seems not very good value .

 

[cuthound]

10 hours ago, matty40s said:

The point of the OP being all that will end up back in the cut as soon as it floods again.

Dredging is about removing , not just lifting it out back onto the flood plain it came from.

 

But the contractors have to consider how they are going to get their future work. ?

 

The root cause of the problem is in whoever wrote the specification for the work. If the work wasn't properly specified to minimise future work then you can't blame the contractor for doing what he was asked to do.

Edited October 15, 2020 by cuthound
Clarification

[Richard T]

When I spoke to the contractor they said that they would have preferred to remove the silt from the site but were instructed to create a berm. The issue is where and how do you dispose of 600 tonnes of material other than to landfill which would be very expensive. Road access to the site is non-existent - the nearest would be at Redhill Marina or Kegworth flood lock.

[matty40s]

1 hour ago, Richard T said:

When I spoke to the contractor they said that they would have preferred to remove the silt from the site but were instructed to create a berm. The issue is where and how do you dispose of 600 tonnes of material other than to landfill which would be very expensive. Road access to the site is non-existent - the nearest would be at Redhill Marina or Kegworth flood lock.

There was road access as there used to be moorings there, has duelling the road removed this?

 

By boat.

Edited October 15, 2020 by matty40s

[Mike Todd]

4 hours ago, MartynG said:

On the Trent at Stoke Bardolph  they have dredged a channel and deposited the material in the middle of the river .

I guess it has ensured future work as the almost inevitable flooding to come may well put it back where it was.

At least they have done something even if it seems not very good value .

 

Most navigational dredging has long been that - taking it out from the same place every year! (Sounds very much like the famous definition of insanity!)

[Momac]

16 minutes ago, Mike Todd said:

Most navigational dredging has long been that - taking it out from the same place every year! (Sounds very much like the famous definition of insanity!)

Seems like job creation scheme.

I expect leaving the material in-situ but redistributed is done to save the cost for removing the material off site, which  would be prohibitive.

[Jerra]

15 hours ago, Richard T said:

The down side is that future floods will wash the silt back into the cut. 

Surely that will depend on how soon there is a flood.   Will the berm not have time to get a mat of vegetation before the next flood?  Afterall the surface of fields doesn't was away in floods or we would have some Lake District valleys totally devoid of soil.

[Momac]

8 minutes ago, Jerra said:

Surely that will depend on how soon there is a flood.  

Which could be sooner rather than later given the time of year.

[Jerra]

2 minutes ago, MartynG said:

Which could be sooner rather than later given the time of year.

Ah so this is a yearly happening.  Despite our climate in the Lakes we only get serious flooding (100 year events) every 3 - 5 years.  Other floods spread over the fields but don't have much flow so don't scour banks etc.

[Momac]

3 hours ago, Jerra said:

Ah so this is a yearly happening.  

Can be  more than once  a year

[Richard T]

4 hours ago, Jerra said:

Ah so this is a yearly happening. 

The Soar can flood at any time of the year and regularly does so several times a year. It has a large flood plain. Above Ratcliffe lock there are two weirs but these have become silted up ( EA responsibility?) so the river takes the line of least resistance which is down the lock cut and the flows over the lock gates back into the river. There will be little chance of  vegitation establishing its self on the berm before the next flood.  The Google extract shows the area. Theree are culverts under the main road to allow flood water to pass under it. The riverloop itself is quite shallow - there is the remains of an old ford close to the 'r' in Soar

 

[Mike Todd]

On 15/10/2020 at 13:03, Jerra said:

Surely that will depend on how soon there is a flood.   Will the berm not have time to get a mat of vegetation before the next flood?  Afterall the surface of fields doesn't was away in floods or we would have some Lake District valleys totally devoid of soil.

Climate change primarily affects the amount of rainfall but the impact if any specific amount will depend on several other factors. In particular the amount of preceding rain will affect the ability of the ground where the rain falls to absorb water. Clearly if the surface of the ground is hard then the rain runs off quickly into larger water courses. On the other hand if the water table is very high then there will also be runoff. Flooding can take place some distance from where the rain falls. 

 

Close to us the famous Boscastle flood was the result largely of heavy rain that fell over a short period on the inland moors.

 

I am guessing but I suspect that any scouring effect once the rain reaches a larger river will depend quite a bit on the pattern of how if falls, as well as the quantity, and any differences in turbulence. Determining the floid pattern in any area us complicated and hence at times the only reliable way is to build a test model, although that can be expensive.

[Momac]

On 14/10/2020 at 21:45, Richard T said:

We were boating on home territory on Monday and went through Ratcliffe lock. We were pleasantly surprised to see that Land and Water had dredged on behalf of CRT the large shoal that had built up during floods over the past years. Speaking to one of the guys doing the job he said that about 600tonnes of silt has been removed. This has been used to build a berm about 1m high with a crown of about 5m. The down side is that future floods will wash the silt back into the cut. The berm will be eroded from both sides. It would have been better if the berm had been started a metre back from the cut edge.

A friend walks his dogs down there and he says its mostly  washed back in now.

[BWM]

On 14/10/2020 at 23:34, matty40s said:

The point of the OP being all that will end up back in the cut as soon as it floods again.

Dredging is about removing , not just lifting it out back onto the flood plain it came from.

 It may even make it worse, as the deposited material will have killed off any vegetation that was holding the original backside together. 

On 15/10/2020 at 07:40, MartynG said:

On the Trent at Stoke Bardolph  they have dredged a channel and deposited the material in the middle of the river .

I guess it has ensured future work as the almost inevitable flooding to come may well put it back where it was.

At least they have done something even if it seems not very good value .

 

 It seems to be standard practice to chuck spoil into the channel by today's contractors, i've witnessed it when piling work has been done on our local stretch of the GU.

[calara]

3 hours ago, BWM said:

It seems to be standard practice to chuck spoil into the channel by today's contractors, i've witnessed it when piling work has been done on our local stretch of the GU.

 

Two different things:-

 

Stoke Bardolph is on a large(ish) river, and dropping the silt on top of a weir essentially stirs it up into the water - which is then carried away by the current. Silt that drops out of solution will be spread over a large area and have a minimal effect on depth. This method has been used on larger rivers for centuries with reasonably good results.

 

Throwing silt into the centre channel of a canal is just plain stupid and needs reporting.

[BWM]

8 minutes ago, calara said:

 

Two different things:-

 

Stoke Bardolph is on a large(ish) river, and dropping the silt on top of a weir essentially stirs it up into the water - which is then carried away by the current. Silt that drops out of solution will be spread over a large area and have a minimal effect on depth. This method has been used on larger rivers for centuries with reasonably good results.

 

Throwing silt into the centre channel of a canal is just plain stupid and needs reporting.

I'm aware of the differences between the two, with practices such as luteing used to shift silt from wharfs. 

 Reporting it achieved nothing, i got the impression that Crt don't cost in spoil removal. On one occasion i spoke to the contractors as they were depositing everything, including large capping blocks into the channel in a bridge entrance, and informed them that i was already scraping the bottom. Their response was to move the work boat further out and covertly shake it out in exactly the same spot. All under the watchful eye of a Crt representative. I attached videos of this to an email which achieved nothing.