Broads Authority Briefing September 2019

[Smoggy]

1 minute ago, grendel said:

actually, its the lack of the weight of ice after the last ice age, the weight has reduced so scotland is rising again

So weight of ice is the reason then.

That is why I sort of mentioned scotland rising and weight of ice.

I was being PC and not mentioning heroin addicts in glasgow getting thinner......

 

[JennyMorgan]

The river Yare, because there is now no commercial shipping to Norwich, has been allowed to tactically silt up since there is no practical need  for deep water. The Yare is the major flush to Breydon Water yet we don't hear of increasing problems of excessive shoaling. there, despite this reduced flush. Yet I hear local talk of mudbanks on Hicking being shifted by a strong, Force 8 wind.  The watermen of old understood the Broads as do some today but such folk were or are not employed by the BA nor were they on relevant committees. Historically local knowledge has tended to be ignored hence the long held accusation that local Broads people needn't apply for the job! Practically gained qualification, university of life, regretfully count for little.

So much information and experience has been lost but perhaps changes are afoot, I quote the Broads Briefing:

Monica Pichler, a PhD student in marine microbiology (UEA) also joins us for a three-month internship looking at water levels in the Broads. She will analyse data recorded over the past 20 years to create new tidal information on water levels throughout the Broads area. This will improve predictions of flooding at 24-hour moorings, dockyard and yacht stations, and our understanding of the relationship between water levels, water quality and biology in Hickling Broad.

Surely an understanding of what is THE major component of the Broads, from both conservation and navigation viewpoints, should have been a priority from day one. Anyway, must be charitable, better late than never!

 

 

[batrabill]

1 hour ago, MauriceMynah said:

I don't agree. One only has to increase the size of the plughole to make the bath drain faster.

 

I strongly believe from what I have read that this is much too simplistic an analogy and that water systems are vastly more complex and hard to understand than these “common sense” ideas would allow for. 

But to stick with this analogy, if you make the plug hole bigger you will run aground all over the bath. 

Meaning if you wish to change the whole system you have to change the whole system. 

[MauriceMynah]

4 minutes ago, batrabill said:

But to stick with this analogy, if you make the plug hole bigger you will run aground all over the bath. 

Love it !!!

[Seagypsy]

1 hour ago, Smoggy said:

I think the wobble is called precession (or similar) and takes about 15,500 years to do a full cycle (or was it 21,500 years?).

Don't forget that scotland is supposed to rising and south of england sinking due to the number of jocks coming down here to find proper jobs (or was it weight of ice? same sort of thing).

Don't know about proper jobs, when I listen to the accents I think a lot of them became MPs

[JennyMorgan]

14 minutes ago, batrabill said:

But to stick with this analogy, if you make the plug hole bigger you will run aground all over the bath. 

But only if the plug hole is too big and the tap has been turned off.

[grendel]

1 hour ago, JennyMorgan said:

But only if the plug hole is too big and the tap has been turned off.

following the analogy further, you have drains that overflow and wash back up the plughole too, bringing with them everything in the drains - or in reality - saltwater surges

[JanetAnne]

Sitting here surrounded by sandbags, flood defenses in place since Sunday, and with the grass standing more chance of being trimmed by a submarine than a lawnmower, (yup Beccles yacht station awash again), can anyone confirm whether this area used to be flooded as often as it is now? Bear in mind that the harbour masters side quayhead had 3 inches of concrete chucked on top of it a couple of years ago as well...

[JanetAnne]

By the way, here are a couple of points from JP himself that may be relevant here.

The first is from 2016 and was the answer to my question regarding dredging the lower Bure and the hump at the mouth of catfield dyke.

Dear JanetAnne,

In the last 3 years the BA has dredged over 70,000m3 from the river Bure, however the modelling that we carried out as part of the Sediment Management Strategy showed that dredging has minimal impact on water levels.

In fact, the Bure Loop acts a throttle in the system and restricts the flow of water heading upstream from Great Yarmouth which is why the waterway specification was restricted by agreement with Natural England to reduce the potential for saline incursion.

Generally speaking, water levels are more influenced by atmospheric conditions and rainfall in headwaters and there is good evidence from the bridge pilot records at Potter Heigham that water levels have increased over the last 30 years.

We have also spent a lot of time, energy and money in agreeing a vision for Hickling which is allowing us to carry out dredging on this very sensitive site, and will include Catfield Dyke in a later phase.

Regards

John

the second from me was in November 2017

 

Good evening,

Just the one question from me this time JP. Its a question I have failed to get an answer to for some years now so I figure ask at the top once again and see what happens...

What constitutes 'navigation'?

The BA is required to maintain navigation, that is not in dispute, but what is 'navigation'?

To maintain water depths at a level which allows the scouts to float their canoe's would still allow navigation but not at a depth needed by the majority of broads users.

Is 'navigation' deemed to be a depth of 3ft, 6ft, or maybe just 6 inches?

So here is my question... What water depth does the BA consider to be reasonable to maintain navigation?

Once we have that established we can all work towards it eh?

 

Good Evening JanetAnne,

Thanks for the question.

The Authority’s functions in respect of maintaining the navigation area are set out in the Norfolk and Suffolk Broads Act 1988 S10 (1).

(1)The Authority shall—

(a) maintain the navigation area for the purposes of navigation to such standard as appears to it to be reasonably required; and

(b) take such steps to improve and develop it as it thinks fit.

This requires the Authority to exercise its judgment.

The navigation area is defined in Section 8 of the Act as:

1) In this Act “the navigation area” means, subject to any variation for the time being in force by virtue of an order under subsection (3) below—

(a) those stretches of the rivers Bure, Yare and Waveney, and their tributaries, branches and embayments (including Oulton Broad) which, at the passing of this Act, were in use for navigation by virtue of any public right of navigation;

(b) the banks of the waterways which make up those stretches; and

(c) Haddiscoe New Cut and its banks;

(d) Breydon Water and the Lower Bure.

The Authority’s Sediment Management Strategy 2007 sets out the ‘ideal waterway specifications’ in terms of depths. These vary across the network from 1.5 metres to 2.4 metres below mean low water springs.

You can find a copy of the Strategy on the Authority’s website with the maps showing both the waterway specifications and recent hydrographic survey information.

The report is at the following link:

http://www.broads-authority.gov.uk/boating/navigating-the-broads/water-depths

Hope that helps – please come back to me if you want any further information.

Regards

John

 

[SPEEDTRIPLE]

11 hours ago, grendel said:

  so scotland is rising again

We`re not talking about Nichola Sturgon here are we?  .

[JennyMorgan]

1 hour ago, JanetAnne said:

a) maintain the navigation area for the purposes of navigation to such standard as appears to it to be reasonably required;

And there lies the problem, the BA itself, which generally means the CEO, is empowered to decide for itself/himself as to what standards it maintains the 'navigation area', wherever that is. For those of us in kayaks it really is anywhere with more than four inches of water!

[Poppy]

On 01/10/2019 at 16:17, BuffaloBill said:

Grendel. I'm sure that you will correct me if I'm wrong, but doesn't the earth 'wobble' on it's axis? If so, does this correspond to that lower graph by any chance? 

Indeed the earth does wobble on its axis , and its orbit isn't circular ,either !

Interesting and readable piece here

https://www.bgs.ac.uk/discoveringGeology/climateChange/general/causes.html

[Timbo]

I wondered if anyone would be interested in this report on the structure of the bridge? I found the comment 'previous investigation of river bed levels shows a marked reduction in depth and flow area at the bridge' quite interesting. Please note the Grade II listed and scheduled monument is not sinking and is structurally sound.

Right, I'll return to writing reports and sucking the common sense out of post graduate students and then teaching 'em 'stuff'. 

[Vaughan]

1 hour ago, Timbo said:

I wondered if anyone would be interested in this report on the structure of the bridge? I found the comment 'previous investigation of river bed levels shows a marked reduction in depth and flow area at the bridge' quite interesting. Please note the Grade II listed and scheduled monument is not sinking and is structurally sound.

Right, I'll return to writing reports and sucking the common sense out of post graduate students and then teaching 'em 'stuff'. 

I wondered when we might be hearing from you, on this subject!    

[ranworthbreeze]

To me the pictures show some movement on the stones that are in the small arches. 

Regards

Alan

 

[SPEEDTRIPLE]

On 03/10/2019 at 10:01, Timbo said:

I wondered if anyone would be interested in this report on the structure of the bridge? I found the comment 'previous investigation of river bed levels shows a marked reduction in depth and flow area at the bridge' quite interesting. Please note the Grade II listed and scheduled monument is not sinking and is structurally sound.

Right, I'll return to writing reports and sucking the common sense out of post graduate students and then teaching 'em 'stuff'. 

"A marked reduction in DEPTH"?. 

22 hours ago, ranworthbreeze said:

To me the pictures show some movement on the stones that are in the small arches. 

Regards

Alan

 

"Movement on the stones that are in the small arches"

And as we All know, the clearance has reduced by a very significant amount now restricting passage to most boats that regularly used to go through it?. 

Less depth, plus less above water clearance means less distance between the river bed and the top of arch?. Of course the bridge HAS'NT sunk, despite, according an earlier post one side is now higher than the other. 

Obviously the river bed has grown taller and the water is going through sideways. Is'nt mother nature amazing?. 

[grendel]

2 hours ago, SPEEDTRIPLE said:

Of course the bridge HAS'NT sunk, despite, according an earlier post one side is now higher than the other. 

surely something like that would have been reported in the survey, it was after all only someones opinion that they though it might have sunk on one side, it could of course easily been an optical illusion caused by the angle of viewpoint.

It is very easy to just pick and choose the bits of a post that we would like to believe, but we have now seen the sea levels data and the bridge survey, so if the bridge isnt sinking, and the sea hasnt risen as much as the clearance has dropped, that just leaves "something else" as the cause, once the known causes have been deducted.

as for one side sinking, the picture in the report does show one arch lower than the other, but then again so does this one from 1926, clearly the herbert woods side arch is lower than the other, and yes there does appear to be more clearance in 1926 than 2011, but then sea level in 1926 was some 75mm below average UK MSL whereas in 2011, it was 100mm above UK MSL, a difference 0f 175mm.

[BroadAmbition]

"something else" as the cause,

Sigh - Really?  Do we really have to explain it yet again?  Increased river levels are down to the lack of dredging on the lower Bure and the 'Hump' or bottleneck in particular. IF (HUGE 'IF') the lower Bure were to be dredged properly as it used to be all year round, especially on the bends / corners right through to the yellow post, then the clearance would drop at PHB no problem.

However - That would also show up the many square miles of silting all over the Northerns that the Ba has allowed to happen over the last 30 odd years and drop them right in the mire.  It's a problem of their own making

Griff

[grendel]

While I probably agree with you Griff, we are trying to find hard data to prove the point, and we are eliminating sea level change (4" over the period we were looking at) and the bridge sinking from the causes, " something else" could well be the bure hump, but we need uncontrovertible data to prove that this is so.

[grendel]

I do however take exception to the elevation drawing in the report, as it fails to show the difference in height of the two side arches, this is an obvious feature as can be seen by the photographs, so to represent it on the survey drawing as the same height could well cause issues at a later time, as a draughtsman it offends my eye to see such a casual misrepresentation called an elevation drawing, it also leads me to wonder if they even measured the clearances on the side arches.(though I can appreciate with changing river levels taking a comparative level might be difficult as you would need to measure all 3 arches in a short span of time.

[BroadAmbition]

It ain't just the Bure Hump - Its the whole lower Bure, especially the corners and from Marina Keys down to the yellow post.  If I get time this evening I'll post up 'My' evidence / reasoning yet again

(MrsG due home today for seven whole days - first time she will have been at home since 28th Aug and I hope to be otherwise 'Engaged' )

Griff

[grendel]

On 03/10/2019 at 12:05, ranworthbreeze said:

To me the pictures show some movement on the stones that are in the small arches. 

Regards

Alan

 

we must remember that the stones we see that have moved are only the facing stones on the outside of the bridge structure, the fact that they were able to realign them in the repairs shows that the underlying structure of the bridge had not altered, just on the visible face the missing stone allowed those surrounding it to also shift slightly.

[grendel]

17 minutes ago, BroadAmbition said:

It ain't just the Bure Hump - Its the whole lower Bure, especially the corners and from Marina Keys down to the yellow post.  If I get time this evening I'll post up 'My' evidence / reasoning yet again

(MrsG due home today for seven whole days - first time she will have been at home since 28th Aug and I hope to be otherwise 'Engaged' )

Griff

I think you would be better occupied looking after mrs Griff this evening, and you have posted your evidence before, but I am sure somewhere out there is the surveyed data for the depths, but the question is then can we find similar river depth data from the 1970's or 1980's that would help prove the case.

empiratical data such as well they dredged all year round in the 1980's and they dont now, is fine and dandy, but actual hard numbers speak volumes more to prove the point, with numbers the actual volume of the flow could be calculated and the reduction in that flow could then be factored into the equation.

[rightsaidfred]

46 minutes ago, grendel said:

While I probably agree with you Griff, we are trying to find hard data to prove the point, and we are eliminating sea level change (4" over the period we were looking at) and the bridge sinking from the causes, " something else" could well be the bure hump, but we need uncontrovertible data to prove that this is so.

That could well help if it is available, it may also help if rather than concentrating on the bridge construction we also take into account that while not quite so obvious the average clearance at Wroxham has also reduced over time, as I don't have the necessary knowledge I ask again is anyone aware of similar changes to the Yarmouth or Southern bridges or the Breydon mudflats? if there hasn't been that in itself indicates a problem with water levels on the Bure being held back.

Fred

[JanetAnne]

By the way, a good friend ran aground on Breydon at low tide as he approached Breydon bridge heading towards Yarmouth. It was during the low tides middle of last month and he was on a wooden broads cruiser (not a yacht). I believe it has been mentioned to the BA but it seems that there may be a build up on the corner between the dolphin and the starboard span as you head east. His boat bogged down noticeably but had enough momentum to push through.