Herring Bridge

[batrabill]

Saw this today on FB. Not definitive proof, but carries more weight with me than what I read in the Daily Mail.

Reproduced with permission

On January 6th, I visited Great Yarmouth to observe the new bridge and make a report on the demasting stations. Using the advanced sonar imaging equipment on my offshore boat, we were able to capture detailed images of the area beneath all three Great Yarmouth Bridges during the ebb tide. With my experience in offshore navigation, shipwreck diving and sonar imaging for fishing and diving, I have a deep understanding of how tidal flows interact with obstacles and its effect on bottom structure.

The findings were quite revealing. Under the Breydon Bridge, the water surface showed distinct creasing near the supports, and the riverbed was eroded to depths of 2 to 3 meters deeper than the surrounding areas. The East section displayed a 1-2 meter scour with a more even bottom.

The Haven Bridge, however, presented a different picture. There was a significant crease on the water surface with an accelerated flow between the supports, and a turbulent current that affected the boat's handling when off throttle. The scouring here was about 3-3.5 meters deep with a noticeably uneven riverbed.

Near the Haven Bridge seaward side, the riverbed was smooth, a condition that persisted up to the Herring Bridge. At Herring Bridge, the water surface was calm, the tide noticeably slower, and the riverbed flat and uniform at about 20 feet in depth. 

Based solely on these observations, the Haven Bridge seems to be the primary bottleneck in river flow, not the Herring Bridge. This could indicate that the issues attributed to the Herring Bridge might be a misdirection. Feel free to post your own observations of how the bridge is interacting with the river channel, of course. You are also aware that Oct-Dec the Broads Catchment received 175% of average rainfall. At the same time the North Sea tides have on average been 36% higher since October, reducing a tiny river gradient even further. Keep reposting these unsubstantiated claims really gets in the way of the conversations that are being have trying to help people in the same place as yourself (if indeed YOU are still underwater).

[marshman]

Interesting observation! However not really different to what I would have expected.

 

 

 

 

[bucket]

Very interesting, do you know who the author is?

[marshman]

Clearly not a  reporter working for the Daily Mail!!!!

[NeilB]

I've had a quick look at some of the local Facebook sites but couldn't find it, do you have a link please or the name of the group?

[grendel]

the only  part I find strange is the use of metric depths everywhere until we get to herring bridge, then all of a sudden the depth is 20 feet was the sudden change in measurement system a deliberate attempt to confuse the issue or a genuine mistake.

it just struck me as an incongruous way of presenting the data.

[batrabill]

Original Post is a reply to a piece on the bridge on The Broads Society page.

https://www.facebook.com/broadssociety

[NeilB]

Looks like a member of the Broads Society took his own vessel to investigate the new de-masting pontoons by the Herring Bridge.

Modern sonar systems are very good and I'm sure the author is very experienced but this does not appear to be an official report by a commercial operation?

Haven Bridge has been there for a long time, we've not had much rain the past week or so yet water levels are still high over 2 months after the original floods.  We've had wet periods before but I cannot remember it taking so long to drain away.

[MY littleboat]

Interesting that the broads Society call them 'demasting stations' (I imagine the author may have been responsible for another post) these are not and are waiting pontoons for bridge lifting. I recently transited the port and was advised that neither pontoon is to be used as these are for the new bridge, which, as it is currently remaining in the open position (For at least the remainder of this year) are not in use.

A recent video of mine highlights that there are 'no mooring' signs still on these pontoons.

There is a mindset change required here, this is a commercial port, and all they are interested in is clearing leisure craft as quickly as possible.

Like others on this forum who have transited haven Bridge many times, it is always a real nightmare - especially when you are forced to transit it at LW due to not lifting for so long, and the side-scanning sonar that alot of vessels now have, paint this common picture. However, The Haven Bridge has been there a long time, the 'Herring' bridge has not, and the recent prolonged flooding may have both as contributory factors, in addition to dredging, farming practices, building and construction, EA water management and water companies - until all stakeholders accept that they have a contributory hand, then there will just be finger pointing and no solution - as no agency, authority or company is ever going to admit an ounce of liability - a little like the Post Office refusing to acknowledge their hand in another problem - even though, just like POL, all of those regulatory bodies, agencies and companies have undoubtedly already had liability discussions with their insurers!

[Wussername]

Pass the parcel comes to mind. 

[Islander]

Just for information, flood warnings for Yare and Waveney. I’m not signed up for the northern rivers but suspect there will be another salt surge.

note how low it was on the night tide. 
Beware overtopping at some moorings if you’re on the rivers at the moment.

Colin 

 

[floydraser]

7 hours ago, grendel said:

the only  part I find strange is the use of metric depths everywhere until we get to herring bridge, then all of a sudden the depth is 20 feet was the sudden change in measurement system a deliberate attempt to confuse the issue or a genuine mistake.

it just struck me as an incongruous way of presenting the data.

Agreed. I thought I was just being picky but the author presents his experience and obviously tries to give the impression he has done a thorough job, then does that. A bit odd. Doesn't alter the facts as presented of course. Maybe he wanted it to sound deeper?

I remember an engineer who used go ballistic if someone mixed imperial and metric measurements on a drawing.

[marshman]

I agree its a trifle odd but I wouldn't dismiss what he says on that basis alone.

He has obviously been around a lot and merely giving his opinion as it was clearly asked for. You will either believe him or not - bit like Americans with Donald Trump!   Ooops - is that a political comment????

[batrabill]

If it wasn’t for those pesky boaters! 
 

You’ve rumbled him. It’s obviously John Packman laying a false trail!

[Bytheriver]

23 hours ago, MY littleboat said:

Interesting that the broads Society call them 'demasting stations' (I imagine the author may have been responsible for another post) these are not and are waiting pontoons for bridge lifting. I recently transited the port and was advised that neither pontoon is to be used as these are for the new bridge, which, as it is currently remaining in the open position (For at least the remainder of this year) are not in use.

A recent video of mine highlights that there are 'no mooring' signs still on these pontoons.

There is a mindset change required here, this is a commercial port, and all they are interested in is clearing leisure craft as quickly as possible.

Like others on this forum who have transited haven Bridge many times, it is always a real nightmare - especially when you are forced to transit it at LW due to not lifting for so long, and the side-scanning sonar that alot of vessels now have, paint this common picture. However, The Haven Bridge has been there a long time, the 'Herring' bridge has not, and the recent prolonged flooding may have both as contributory factors, in addition to dredging, farming practices, building and construction, EA water management and water companies - until all stakeholders accept that they have a contributory hand, then there will just be finger pointing and no solution - as no agency, authority or company is ever going to admit an ounce of liability - a little like the Post Office refusing to acknowledge their hand in another problem - even though, just like POL, all of those regulatory bodies, agencies and companies have undoubtedly already had liability discussions with their insurers!

Herring Bridge opens to road traffic on 1st Feb 2024

[MargeandParge]

33 minutes ago, Bytheriver said:

Herring Bridge opens to road traffic on 1st Feb 2024

Probably for boaters and broads lovers on the 1st of April any year you fancy.

Kindest Regards Marge and Parge 

[MY littleboat]

15 hours ago, Bytheriver said:

Herring Bridge opens to road traffic on 1st Feb 2024

Thank you, sorry, I had missed that announcement!

[MY littleboat]

On 24/01/2024 at 20:53, floydraser said:

Agreed. I thought I was just being picky but the author presents his experience and obviously tries to give the impression he has done a thorough job, then does that. A bit odd. Doesn't alter the facts as presented of course. Maybe he wanted it to sound deeper?

I remember an engineer who used go ballistic if someone mixed imperial and metric measurements on a drawing.

Although the poster made detail of being extremely experienced in this field and went to great lengths to describe in pseudo-scientific terms what his impression was, it was neither scientific or can be regarded with any accuracy as to present an accurate picture, readings would be required at all states of tide to calculate volume flow, flow rates and whether the estimated volume in equals volume out - this would also need repeating at different tide-cycle points - simply neap and springs. Whilst I agree that small boat sonar is better than before, it certainly isn't showing current differences (under currents etc) so, whilst this writer, has a well equipped sea-going boat, and has significant detailed experience, it still does not produce any sort of scientific bulk data which can be analysed and assessment drawn for the purposes of flood alleviation.

At university I learnt one thing - evidence sources that are unsupported or opinions should be treated as just that - a hypothesis which needs testing in order to validate or ignoring.

The most worrying aspect of this report are the two final statements;

You are also aware that Oct-Dec the Broads Catchment received 175% of average rainfall. At the same time the North Sea tides have on average been 36% higher since October, reducing a tiny river gradient even further. 

It may be so that rainfall is increased - actually I cannot find reference to 175% and is not supported by data from the Norfolk Weather Centre and did not significantly exceed the 30 year average between 1985 and 2015 source - Climate & Weather Averages in Norfolk, England, United Kingdom (timeanddate.com)

EDP picks a figure of 125% here - Norfolk weather in 2023 was among wettest years on record | Eastern Daily Press (edp24.co.uk)

As for the statement with a calculated tidal percentage - what is that statistic in comparison to, and where the heck has it come from?

Lastly, Keep reposting these unsubstantiated claims really gets in the way of the conversations that are being have trying to help people in the same place as yourself (if indeed YOU are still underwater).

Why suddenly complete what appears to be a thoughtfully written submission with some passive aggressive threat?

 

[Vaughan]

On 24/01/2024 at 17:26, NeilB said:

Haven Bridge has been there for a long time, we've not had much rain the past week or so yet water levels are still high over 2 months after the original floods.  We've had wet periods before but I cannot remember it taking so long to drain away.

I think Neil makes the strongest point here.  Something or other, has happened to cause this latest flooding.

Google tells me that the Haven Bridge was opened by the Prince of Wales in 1930.  He, that would be, who became Edward VIII before he abdicated.  So it has been there for a great deal longer than "the last shower of rain"!

There is also no doubt, however you see it, that the Herring Bridge has narrowed the river at the Fishwharf by just over a third of its previous width.

The main principle of hydraulics is that you cannot compress water.  A given volume of water in one place will be the same volume when you move it somewhere else.

The Haven Bridge is a restriction to the ebb tide but from then on, the water flows straight out to sea in a wide river with more or less parallel banks.  So whichever way you look at, the Herring Bridge will be a constriction of this flow.  As it has nowhere else to go, there will be a back pressure in the water upstream towards the Haven Bridge, which will further restrict the flow through that bridge.

You get exactly the same effect in a boat's cooling system, where a restriction in the flow at the heat exchanger will cause a back pressure in the raw water pipes and strip the blades off the pump impeller.

Conversely, the Herring Bridge will also constrict the incoming tide by a third and may help to lessen the incursion of North Sea surge tides.

[marshman]

What and where is the Norfolk Weather Centre - any average figures from them would be  suspect anyway as the weather in W Norfolk is very different to that within the Broadland catchment area.

You will never get any scientific data so why not accept anecdotal evidence, instead of just dismissing it purely because it doesn't agree with what others may believe! The world these days is just too full of experts and people believing they are right, and everyone else is wrong!

[Vaughan]

Try thinking of the river in Gt Yarmouth between the two bridges as a water tank, of a given volume.

If you restrict the outflow from the tank you will therefore restrict the inflow, since you can't compress the water and you can't fill the tank any higher than the level of the tide.  Water does not flow uphill.

Archimedes, and all that.

[batrabill]

I think the original FB poster would like to respond - he has some "pseudo-scientific" data.

 

[grendel]

3 hours ago, marshman said:

The world these days is just too full of experts and people believing they are right, and everyone else is wrong!

all the more reason not to accept the anecdotal evidence in the face of the inconsistencies

[FairTmiddlin]

22 hours ago, Bytheriver said:

Herring Bridge opens to road traffic on 1st Feb 2024

Be aware that the ceremony starts at 11 am, but ordinary traffic is not expected to be able to use the bridge until after 3 pm.

[marshman]

Grendel - presumably your comments equally apply to the underlying issue purporting to be the cause of this flooding!!!