Flood Planning

[MY littleboat]

On 29/11/2023 at 10:15, Vaughan said:

The Haven Bridge has been there for a very long time and the river system has "got used to it".  By this, I mean it is part of the reason why the tide turns on Breydon at least an hour before it turns on the Bure.  On a different thread lately, we were shown a picture of soundings over this area, which showed a pronounced sand bar in the Yare just upstream of the Bure junction, which is obviously the result of silty water coming down the Bure, being diverted up onto Breydon for that last hour before slack water.  Dredging that, would not be such a bad idea either!

Marshman and I are wherrymen (in all humility) who know very well that the ebb tide, especially on the Yare, is a great deal stronger than the flood.  This is because of the rainwater outfall coming down from those 3 rivers which, between them, drain almost all of north and central Norfolk.  I forgot to mention the Waveney, which drains the rest of south Norfolk!

In the article, the EA claim part of the flooding is owing to pump failures.  But these are only the pumps which drain the marsh meadows, which just for once, are acting exactly as they were always meant to, by retaining the flood water!

 

I can only add from the point of view of travelling the Yare through Yarmouth itself and since the new bridge foundations were placed, the ebb is so much worse and faster - I have recent film of this, but fear that so few boats will have used the commercial part of the river since Haven Bridge was inactive for so long, that it may have gone unnoticed. 

I feel that the statement that 'dredging reduces flooding is a myth' that has been perpetrated by BA this week is very concerning in that EA spend a disproportionate amount of funding in keeping the Fens waterways and drainage channels dug to sufficient depth.

There seems an almost total disregard to addressing that still, today, water levels have not reduced significantly, nor that just a couple of months ago that the government gave housing developers carte blanche to build without needing to implement either drainage or flood investment plans.

Whilst there is a lack of ownership for the issue, there will be no solution, but with the Broads, for many, especially novice users, being a somewhat dangerous place to be at present, I am disappointed that BA are not being more proactive in their approach to at least acknowledging issues instead of putting their hands in their deep pockets and say 'its not my fault gov'

[MY littleboat]

DO NOT TRY THIS IN YOUR BOAT - This is a piece of River I know well and understand the capabilities of my boat - no riverboat would be able to turn in this ebb.

I have been watching river levels for some time, prior to Storm Cairan, bob or whatever it was called, I captured the following footage - it has not been published elsewhere, but thought that I would share it for those forum members who would not be able to access this part of the river. I needed to 'get out' of the Broads and needed to pass under the Bascule Bridge. I can do this by dropping my radar arch, but unless I am lined up perfectly straight, this isn't going to happen - and given the very strong eddies, is not an easy fete.

For reference, there is never a 'slack' period in this part of the river, it runs one way, has a period of convoluted current and then quickly builds as the water re-floods.

Haven Bascule bridge has two solid piers and the side spans allow water to pass under and is of a more traditional design whilst the new Gull-Wing Bridge is designed for heavy commercial road traffic and appears to be solid, restricting more than a third of the navigable channel.

I have been concerned that the air draft at GY Haven Bridge has been above published datum at LW for a very long time, suggesting river levels are higher, and therefore the air draft is reduced. This has probable gone unnoticed as the Bridge has been out of actions for a very long period of time and very few users have the capability of passing under the bridge into the commercial port.

Dredging in all commercial ports is necessary to both maintain depth for draft but also to ensure water levels do not rise higher than the working parameters of the quays - why then does this theorem, which ensured Breydon Water was dredged whilst under the remit of the GYPA not hold weight with BA?

[MY littleboat]

On 29/11/2023 at 09:48, marshman said:

To be fair to the situation, we have had a lot of rain these last 6/8 weeks or so - even Monday we had another 15mm or so onto saturated ground.

BUT no one has died and generally its only marsh or grazing marsh that has suffered and done what its designed to do.

In all of this talk of class actions, has everyone forgotten about Haven Bridge? I am sure that that is narrower and if it is does this not negate the issue somewhat? Figures given for the Herring Bridge seem to vary quite a bit.

As far Meantimes comments are concerned,  the tides in the Broads are unusual - in normal conditions, I always worked on 5hrs of flood and 7 of ebb to allow for the additional water coming downstream. Its certainly not 6 and 6 as it is out in the sea which is why the Aweigh app can get it wrong. Tides in the Broadland area have always had a mind of their own, being affected by so many factors.

And although its pretty irrelevant to the flooding and bridge issue, at New Mills Norwich there is no weir as such but actual sluices which are controlled, I guess by the EA, thereby actually controlling the discharge from the upper reaches.

Absolutely agree, however, I don't think the water retention has been over just recent weeks, I have seen regular moorings that I visit much higher over the past year - 2 years - although this is anecdotal, I would have expected BA to have credible and concise data on this - after all other authorities gather exactly such data - it seems as though the 'perfect storm' that BA describe may need to be re-named 'sleep walked into this'

[marshman]

Here we have a classic Forum conundrum - one poster says one thing, another says the opposite concerning the tidal stream!

Dredging in one place will only move that volume of water elsewhere, and I just cannot agree that the Broads are "a dangerous place" - the flooding of marshes etc" is exactly what is intended - why has it become a "dangerous place"? Marshes have flooded before and release it slowly, and it is not unusual for some areas to flood, such as Horning Ferry, Geldeston Lock and Brundall in the winter. Indeed it can happen in the summer- it was not that long ago that the Ferry Boatyard had to rescue large numbers of cars by tractor and trailer and that was not in the winter!

Whilst the sandbar may be present, its hardly altered the pattern of the ebb running longer down the Bure - that was happening 50 years ago with slack always being an hour or so later. Indeed I think its discussed in the Coot Club or perhaps the Big Six!

And lets finally perhaps squash this possible myth about Herring Bridge restricting the flow - according to the figures, it may have narrowed the river at that point marginally but it still has a stated width of 150 feet, whereas Haven Bridge has a width of 88' - its probably a lot deeper by Herring Bridge too. So now someone more knowledgeable than I can let me know how it can actually restrict flow when its wider and probably deeper?

The biggest place danger in Norfolk from river flooding is Southtown Great Yarmouth and if it overtops the harbour where the walls have just been raised again to prevent this happening then we could well see actual loss of life - apart from a few riverside properties the current spell has seen NO loss of life and relatively little damage to property - things have been worse inland with some places flooded causing extensive damage to property - I think Framlingham was pretty badly affected property wise, certainly more so than round here as people had to be rescued by boats.

Always be aware of unintended consequences of suggesting perhaps possible solutions!

[Smoggy]

I've been through around half ebb and flood and considered only a minor flow increase through the herring bridge piers over the rest of the river compared to the flow difference through haven, I have often seen the best part of 8" level difference (probably more but it's tricky to judge from the helm) between the upstream edge of haven bascules and downstream end, I didn't notice anything like it through herring.

As a side note I see from the latest NTM from GYA that transit is expected to be booked 2 hours ahead of passing herring bridge wether lift required or not which I find very strange as I've never notified them of going under haven till past it just to let them know I'm coming through and so any port traffic also hears.

I suspect I wouldn't have turned that close to haven on the ebb but then again I may have done exactly the same as it's very hard to judge the distance from video, I've turned and stemmed there a few times waiting for the water to drop a bit more.

[dom]

I actually run a website which regularly fetches live river level data from the Environment Agency's API every 30 minutes. Presumably, there are monitoring stations upstream of Great Yarmouth from which data can be sourced?

I don't know offhand how much historic data is available from the API and at what point you might have to make an FOI request for older data - but surely this could be used to establish whether there was a quantifiable change after the bridge restriction was introduced. To my mind, you'd either see levels falling less at low tide, as the water is held back, or a shorter slack water period?

[oldgregg]

The trouble with their API is that most of the data is only refreshed once or twice a day.

I think this is mainly because a lot of the monitoring stations were installed quite a long time ago and so the kit is pretty unsophisticated and there are probably costs associated with sampling more frequently.

You'll note that some stations are updated a few times a day when exceptionally high water levels are expected. Knowing how public sector procurement and service contracts work, I suspect they will be paying a fee per request from the monitoring station.

If you extrapolate that data against time, and plot it against tide tables then there is a lot that can be learnt from it. I was running a data model that did just that over the past few years, with the view to sticking in an App (my day job) but I have parked the project because I just don't have the spare time.

[dom]

I just took a look at Burgh Castle's level monitoring and I think you're probably right about the API refresh frequency - but the raw data is being sampled every 15 minutes, so would probably be available by less programmatic means.

I'm currently listening to the very long recording of the BA's nav committee meeting, but will try and take a look later to see if I can get long term trending data. I have managed to get some long term data with min and max levels by day. Just need to get my head around whether that is enough to use to look for a trend.

[marshman]

Presumably it would also hinder incoming tides - you cannot have it both ways!!!!

[oldgregg]

1 hour ago, dom said:

I just took a look at Burgh Castle's level monitoring and I think you're probably right about the API refresh frequency - but the raw data is being sampled every 15 minutes, so would probably be available by less programmatic means.

I'm currently listening to the very long recording of the BA's nav committee meeting, but will try and take a look later to see if I can get long term trending data. I have managed to get some long term data with min and max levels by day. Just need to get my head around whether that is enough to use to look for a trend.

Yeah, so they update the website from the data on a set interval but the data that's feeding the DB is far less frequent.

If you look at the XML, it shows you the installation date of the stations. Some are pretty ancient, and while they've probably been upgraded I suspect the remote locations they're in mean that connectivity is a problem (and a cost). 

[rightsaidfred]

Once again it seems we are in the realms of who knows best Man or Nature and who can control who, we need to rember that a fundamental law of nature is that for every action there is a reaction, the current situation is a combination of weather conditions we have no control over and the more we try and fix it the more problems we will create elsewhere, and yes I am affected by the current water levels like everyone else.

Fred

[fendoff]

You just couldn't make this up.

EDP article this morning is shocking about the New Bridge.

It just beggers belief that people we trust to spend £120 million on a new Bridge would not have taken the whole Broads system into account. BA and EA should hang their heads in shame for not stopping it.

EDP  Article

[Bernard]

https://www.edp24.co.uk/news/23962352.great-yarmouth-third-river-crossing-flood-warnings-revealed/?ref=socialflow&fbclid=IwAR3UZABEAfc1FhCNY29DY3S-gcjBoLG4v8vUxa3NTnAqCkbo7_PIP27efgg

[ExSurveyor]

Given that construction started in January 2021,

The foundations would have been in place since at least late 2022 and the framework since late 2021. Yet the prolonged flooding this year is being blamed on the new bridge obstructions that has been in place for two previous seasons.

 

[Smoggy]

I did see on the local news yesterday that farmers were moaning about the flooding on the grazing marsh, it was noticable how many times the word marsh was used and no one pointed out that that is what marshes do.

If we want to use flood plain we have to expect it to flood.

[dom]

7 minutes ago, Smoggy said:

I did see on the local news yesterday that farmers were moaning about the flooding on the grazing marsh, it was noticable how many times the word marsh was used and no one pointed out that that is what marshes do.

There's been one interesting comment made by a farmer, who stated that water was running the wrong way, from an established flood plain back onto farming land. That would suggest the volumes of water are exceeding what the plains can traditionally cope with.

[dom]

3 hours ago, fendoff said:

It just beggers belief that people we trust to spend £120 million on a new Bridge would not have taken the whole Broads system into account. BA and EA should hang their heads in shame for not stopping it.

If you read the in-depth risk assessment, the modelling system had significant limitations and couldn't model some feasible real world scenarios within the harbour itself.

It's interesting to hear that RYA raised concerns about the comments on the risk assessment.

[marshman]

One of the farmers interviewed was Mr Cator although I cannot remember which farmer was moaning about it running off the grazing pastures - that would suggest that it could well be an old grazing marsh that had been ploughed up and in my view probably is marginal land. If that is the case who would be surprised?

Too many of the old grazing pastures have been ploughed up and turned into "arable" land e.g. land up near Billockby on the old Yarmouth Road . Why should anyone be surprised - they flooded or are very wet almost every year so let it revert to its proper usage. I know, I know, the profit margin is less!!!!!!

[MY littleboat]

On 01/12/2023 at 14:03, Smoggy said:

I've been through around half ebb and flood and considered only a minor flow increase through the herring bridge piers over the rest of the river compared to the flow difference through haven, I have often seen the best part of 8" level difference (probably more but it's tricky to judge from the helm) between the upstream edge of haven bascules and downstream end, I didn't notice anything like it through herring.

As a side note I see from the latest NTM from GYA that transit is expected to be booked 2 hours ahead of passing herring bridge wether lift required or not which I find very strange as I've never notified them of going under haven till past it just to let them know I'm coming through and so any port traffic also hears.

I suspect I wouldn't have turned that close to haven on the ebb but then again I may have done exactly the same as it's very hard to judge the distance from video, I've turned and stemmed there a few times waiting for the water to drop a bit more.

It probably looked closer than it was! You are right that it is now lifting again, but hasn't been for a while - yes I have seen huge tidal differences there.. sounds like we have the same idea - interesting when you get to the piers sometimes!!

 

[MY littleboat]

On 01/12/2023 at 13:41, marshman said:

Here we have a classic Forum conundrum - one poster says one thing, another says the opposite concerning the tidal stream!

Dredging in one place will only move that volume of water elsewhere, and I just cannot agree that the Broads are "a dangerous place" - the flooding of marshes etc"

Thank you Marshman for correcting my ramblings!

You are absolutely right and no loss of life is fantastic. I concur that I may have used the wrong word in 'dangerous' however specialist rescue teams have been incredibly busy over recent weeks due to increased risk, even where situations just needed a pair of wellies!!!! - sadly that is something we have to assess rather differently now to years ago.

In real terms 'risk awareness' has led to alot of 'rescues' over recent years for situations that you or I may simply wait out, however this has the disproportionate knock on effect of increasing the perceived 'risk' especially with Breydon etc. And I do thank our volunteer and professional responders in all of those cases - often some of our responders have been more than happy to oblige as it allows them to put their training to good practiced use and ensures that more serious incidents are responded to well.

And  I also agree with your comments about the Gull wing bridge as it is surely the volume of water and I should be clearer that I am referring to the fast ebb around Haven House, which for sometime, I watched on a regular basis! (Yes I need to get a life).

I personally make no recommendations, just sharing a short video so that others may appraise the situation for themselves, and offering that BA should be collating accurate data and recognising that waterside business and residential property has been severely affected. 

The issue is that there are those who really do know the Broads - not just the waterways, but the way that the systems of drainage and farming are interlinked, people such as yourselves, who in the past knew the right thing to do. Nowadays we have so many different agencies, all with their own priorities, and understanding the real reason (Which may actually be a complete fluke, but also may not) needs open, careful and accurate assessment

[Vaughan]

9 hours ago, MY littleboat said:

Nowadays we have so many different agencies, all with their own priorities, and understanding the real reason (Which may actually be a complete fluke, but also may not) needs open, careful and accurate assessment

When I look back to all the debate about a flood barrier, back in the 70s, (when it almost got built) I can see how right we were, in Broadland, to protest strongly enough to get it cancelled.  It was quite a fight at the time and our fear was that once it was built it would be a perfect opportunity for all the "experts" to come along with their own agendas and mess about with it.

Imagine if you are a farmer, you would want to lower the water level so as to grow more crops on the land.  But if you are a birdwatcher (owning such a huge amount of Broadland as they now do) you would want to raise the levels, so as to "re-wild" the wetlands and provide a habitat for the beavers.

Just imagine if we had a barrier today, and just how many committees would have to sit and "work with partners" before anyone actually summoned up the courage to work out which button to push.

[MY littleboat]

4 hours ago, Vaughan said:

 But if you are a birdwatcher (owning such a huge amount of Broadland as they now do) you would want to raise the levels, so as to "re-wild" the wetlands and provide a habitat for the beavers.

 

Have a really close look at what is actually happening and the future proposals around Martlesham creek and the Deben. The financial might behind these 're-wilding' schemes is truly frightening

[Vaughan]

1 hour ago, MY littleboat said:

The financial might behind these 're-wilding' schemes is truly frightening

I have also described it as sinister.

Perhaps we are beginning to see one of the underlying and historical problems of the Broads : that is, that we pay for it through our river tolls, but we don't own it.

I should think well over half of the Broads area is owned by the Landed Gentry on the farming estates*, who can charge what they like to moor on their river banks, with impunity and at the same time use enormous political influence.

Probably most of the other half has now become acquired by the bird watchers and/or the National Trust, who quite clearly have their own vision of the future.

It was the farmers with a strong political lobby who forced through the building up of the flood banks in the marshes and it is the RSPB who now wish to close off all of the marsh and wetland that they now control, in case the public frighten their birds!   Or beavers, or sea eagles.

It is not a very healthy future for Broads boating as we have known it and it has now become almost totally un-democratic.  We have not voted for the BA, the EA, the farmers ; nor the bird watchers, but they are the ones who now call the tune.

 

* This is not a criticism as such : I am just identifying the status quo.

[marshman]

I agree with a lot of what Vaughan says but it is a common mistake hereabouts to confuse the RSPB and the Norfolk Wildlife Trust - the latter is a whole lot more than just twitchers and do a better job than the the RSPB. Fortunately the RSPB own very little on the Broads, only Sutton Fen which has always been very private and the Strumpshaw Reserve.

The NWT have just bought and will manage some pasture, part of the Lower Wensum Valley, but almost in the City along by the waterworks and the old May & Baker factory on the ring road - the visitor centre eventually will work closely with locally deprived schools and this must be a plus. The Council don't help introduce nature to the people who they are supposed to educate and it is left to charities to do it - and good luck to them. Some areas of Norwich should benefit from such schemes.

I won't add my views about the large private landowners, one of whom does more harm than good and is adept at getting his face on the local news, but you have heard my views often on these avaricious individuals - enough said!!!

[Bytheriver]

3 hours ago, marshman said:

I agree with a lot of what Vaughan says but it is a common mistake hereabouts to confuse the RSPB and the Norfolk Wildlife Trust - the latter is a whole lot more than just twitchers and do a better job than the the RSPB. Fortunately the RSPB own very little on the Broads, only Sutton Fen which has always been very private and the Strumpshaw Reserve.

The NWT have just bought and will manage some pasture, part of the Lower Wensum Valley, but almost in the City along by the waterworks and the old May & Baker factory on the ring road - the visitor centre eventually will work closely with locally deprived schools and this must be a plus. The Council don't help introduce nature to the people who they are supposed to educate and it is left to charities to do it - and good luck to them. Some areas of Norwich should benefit from such schemes.

I won't add my views about the large private landowners, one of whom does more harm than good and is adept at getting his face on the local news, but you have heard my views often on these avaricious individuals - enough said!!!

Do RSPB not own or lease the marshes between Berney Arms & the A47 They were certainly involved in the Licencing Application for a Bistro a few years back as well as the IDB Planning Application for Halvergate &  Loughlin Marshes?