Another series of lows and Storm Dennis

[peterboat]

Just now, Graham Davis said:

There has been a paper published (will try to find it) that suggests that unless you can dredge the whole river, all the way to the sea it does little, and could actually make the situation worse>
These for a start.
https://www.sepa.org.uk/media/147022/floods_dredging_and_river_changes.pdf

https://www.ciwem.org/policy-reports/floods-and-dredging-a-reality-check

I think that in rotherham it would a river that should be deep isn't anymore and now we have floods constantly! Flood defense is only the same building banks is only making the river deeper

[Naughty Cal]

9 hours ago, peterboat said:

I think that in rotherham it would a river that should be deep isn't anymore and now we have floods constantly! Flood defense is only the same building banks is only making the river deeper

You also have all the water from Sheffield that is now held between flood walls and channeled through the city as quickly as possible to contend with.

 

Flooding in Rotherham and further downstream has only been made worse by the "improved" flood defences that defend Sheffield from flooding.

 

If you stop the water escaping onto it's flood plains you just push it downstream faster and make the problem worse elsewhere.

 

Still no let up in the rain!!

[ditchcrawler]

Pee it down here in Suffolk today

[Athy]

It's raining here and is forecast to continue doing so all day. It's a tribute to the efficiency of the Middle Level Commission that the Old River Nene doesn't appear to have risen an inch during all the recent wet weather.

[matty40s]

Awful weather, had to buy suncream yesterday.

[peterboat]

58 minutes ago, Naughty Cal said:

You also have all the water from Sheffield that is now held between flood walls and channeled through the city as quickly as possible to contend with.

 

Flooding in Rotherham and further downstream has only been made worse by the "improved" flood defences that defend Sheffield from flooding.

 

If you stop the water escaping onto it's flood plains you just push it downstream faster and make the problem worse elsewhere.

 

Still no let up in the rain!!

Exactly the Rother used to take fully loaded Sheffield size boats up to hovis, now a normal narrow boat can't get up there without grounding and it and the Don have trees growing in it! Before flood defense work dredging the rivers and putting those dredgings on the fields should be the first job 

[sirweste]

34 minutes ago, peterboat said:

Exactly the Rother used to take fully loaded Sheffield size boats up to hovis, now a normal narrow boat can't get up there without grounding and it and the Don have trees growing in it! Before flood defense work dredging the rivers and putting those dredgings on the fields should be the first job 

 

Dredging will not make a significant difference. There a link to a report explaining why in the other thread.

[Athy]

10 minutes ago, sirweste said:

 

Dredging will not make a significant difference. .

It would surely make a difference to navigation, on which PB was commenting.

[peterboat]

8 minutes ago, sirweste said:

 

Dredging will not make a significant difference. There a link to a report explaining why in the other thread.

Cobblers to the report is all I can say, its the cost of dredging they are trying to avoid!

The Don and Rother for most of the time are empty and severely blocked along their lengths so as it rains they fllod by 4 to 5 feet if the were at their proper depth  the full length they wouldnt flood same as the river Hull which is under a third of its size and depth

[Dr Bob]

1 hour ago, peterboat said:

Cobblers to the report is all I can say, its the cost of dredging they are trying to avoid!

The Don and Rother for most of the time are empty and severely blocked along their lengths so as it rains they fllod by 4 to 5 feet if the were at their proper depth  the full length they wouldnt flood same as the river Hull which is under a third of its size and depth

I've not read the report (where's the link?) but I would have thought dredging has to help.

If you take out 100 cu metres of crud from the bottom of the river then that river will then take 100cu metres more water at that point to achieve the same level. The question then is how much water causes the flood and can you dig that much out. I think that we should review the policy on dredging and accept the crud can be spread on the land. Are our fears of contamination too extreme? (which would then make the economics of dredging far more advantageous to flood defences which only serve to move the water downstream to the next unprotected flood plane).

[ditchcrawler]

5 minutes ago, Dr Bob said:

I've not read the report (where's the link?) but I would have thought dredging has to help.

If you take out 100 cu metres of crud from the bottom of the river then that river will then take 100cu metres more water at that point to achieve the same level. The question then is how much water causes the flood and can you dig that much out. I think that we should review the policy on dredging and accept the crud can be spread on the land. Are our fears of contamination too extreme? (which would then make the economics of dredging far more advantageous to flood defences which only serve to move the water downstream to the next unprotected flood plane).

Just seen this one about lack of funding https://www.theguardian.com/commentisfree/2020/feb/23/tories-ignored-flood-advice-austerity-pitt-review?CMP=Share_AndroidApp_News_Feed

[Traveller]

On 22/02/2020 at 12:19, ditchcrawler said:

Here in Suffolk we probably had more wind last night than  both the other two storms, but we have got off very lightly over here

Agreed. Been pretty wild and relentlessly wet and windy but we have been lucky over here. Went across to Fox's in March for a few days to do a bit on the boat. Much the same there and they have not had to drop the marina flood barriers so far. The start of my trip up to Crick looks a long way off but at least the boat is nicely accommodated. Better than what was a river side mooring on the Little Ouse, outside the Ship.

Edited February 24, 2020 by Traveller
fat fingers

[ditchcrawler]

1 minute ago, Traveller said:

Agreed. Been pretty wild and relentlessly wet and windy but we have been lucky over here. Went across to Fox's in March for a few days to do a bit on the boat. Much the same there and they have not had to drop the marina flood barriers so far. The start of my trip up too Crock looks a long way off but st least the boat is nicely accommodated. Better than what was a river side mooring on the Little Ouse, outside the Ship.

Had some very big level changes when I moored at Floods Ferry. It use to worry me as I was moored with a centre line from the roof

[Traveller]

2 minutes ago, ditchcrawler said:

Had some very big level changes when I moored at Floods Ferry. It use to worry me as I was moored with a centre line from the roof

Not so good. Have never moored at Floods Ferry, not even when I was full-time on the Middle Level. It seems that I was either in Fox's or on the river Nene. Never found the ML much of a cruising area really but enjoyed it at Fox's. That was back when Charlie was alive.

[ditchcrawler]

11 minutes ago, Traveller said:

Not so good. Have never moored at Floods Ferry, not even when I was full-time on the Middle Level. It seems that I was either in Fox's or on the river Nene. Never found the ML much of a cruising area really but enjoyed it at Fox's. That was back when Charlie was alive.

Fox's and Bill Fen often close the gates in the winter

[Traveller]

11 minutes ago, ditchcrawler said:

Fox's and Bill Fen often close the gates in the winter

They do but speaking to Alan at Fox's he tells me they have not been closed once this winter.......so far!

 

[Markinaboat]

4 hours ago, matty40s said:

Awful weather, had to buy suncream yesterday.

Be careful you don't trip down those steps at your time of life Matty! ?

[magpie patrick]

3 hours ago, sirweste said:

 

Dredging will not make a significant difference. There a link to a report explaining why in the other thread.

We had this argument in Somerset 6 years ago - the pattern is not disimmilar

 

Stop dredging, 20 years later there are unprecedented floods, but apparently not dredging wasn't the issue

 

Then, without actually admitting anything, the EA dredged the rivers again....

 

A lot of the problem is the difference between theory and practice - the theory saying that dredging for 200 plus years wasn't necessary, experience says otherwise

[ditchcrawler]

Surly it depends where you dredge, If you dredge from the floodplain down to a town then the water will come faster, if its below the town it will help the water get away, but what if there is another town. village a bit further down

 

[peterboat]

2 hours ago, Dr Bob said:

I've not read the report (where's the link?) but I would have thought dredging has to help.

If you take out 100 cu metres of crud from the bottom of the river then that river will then take 100cu metres more water at that point to achieve the same level. The question then is how much water causes the flood and can you dig that much out. I think that we should review the policy on dredging and accept the crud can be spread on the land. Are our fears of contamination too extreme? (which would then make the economics of dredging far more advantageous to flood defences which only serve to move the water downstream to the next unprotected flood plane).

I think its the sheer cost that stops them, its subject to EU imposed landfills tax and every load has to be tested,  according to ian who used to have a dredging company it mostly just used to go onto the land to be spread and plowed in, in affect just returning to where it had come from. Maybe things will change now who knows? What I do know though is trees growing in rivers effects flow and causes problems that wernt there before 

Just now, ditchcrawler said:

Surly it depends where you dredge, If you dredge from the floodplain down to a town then the water will come faster, if its below the town it will help the water get away, but what if there is another town. village a bit further down

 

You dredge from end to end  putting the dredging s back on the fields 

[WotEver]

2 hours ago, Dr Bob said:

I've not read the report (where's the link?) but I would have thought dredging has to help.

If you take out 100 cu metres of crud from the bottom of the river then that river will then take 100cu metres more water at that point to achieve the same level.

But if the river has locks (like the Avon) then the level will remain the same, surely?

[magpie patrick]

3 minutes ago, ditchcrawler said:

Surly it depends where you dredge, If you dredge from the floodplain down to a town then the water will come faster, if its below the town it will help the water get away, but what if there is another town. village a bit further down

 

What it really depends on is not changing a regime on a whim - dredging in new places may make flooding worse - stopping dredging where it's historically occured will make things worse

[WotEver]

4 minutes ago, peterboat said:

EU imposed landfills tax

Hopefully one regulation we can happily dump in due course. 

[TheBiscuits]

1 minute ago, WotEver said:

Hopefully one regulation we can happily dump in due course. 

I don't think incinerating dredging spoil is much of an improvement!

[magpie patrick]

1 minute ago, WotEver said:

But if the river has locks (like the Avon) then the level will remain the same, surely?

It would be good if fluid dynamics in flood were as simple as that - they are not

 

A crude model will use the capacity at the weir, a more sophisticated one will look at dimensions of the river as well - and any model may be inaccurate when conditions push the envelope of the model. 

 

My understanding is good enough to say "it's not that simple", I sub-contract to the real experts to get the answers