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Dredging - Lowe Bure - Lack Of Maintenance


BroadAmbition

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Here's something to get the grey matter pondering.  Feel free to debate, fill it full of holes or otherwise.

Of course you can publish the whole or any part of it anywhere else you see fit too

Enjoy:-

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There has been a lot of talk and media interest lately of flooding around the Northern side of the Broads from Gt Yarmouth up river to the head of navigations on the rivers Bure, Ant, Thurne and associated tributaries.  There has also for years now been ever reducing average headroom at Potter Heigham bridge.

Here’s my take on it.  None of it scientific.  I’ts based on what I can see, common sense, talking to local businesses, Broads men and women that work the area and call it home and my history of visiting / using the Broads since 1960.

Before the Broads Authority was formed and came into being the Broads, rivers, moorings etc were managed by the Gt Yarmouth Port Authority Commissioners.  There were just six of them in the shoreside office.  The rest of the staff were out around the maintaining the rivers, dredging, moorings, trees, scrub marshes, river inspectors etc.

Leading up to the late 80’s there were two grab bucket cranes either side of the Lower Bure.  They were permanently on standby ready to dredge any areas that formed a build up of silt especially on the bends.  They were not in operation every day but they were there ready to go when called upon.  River depth was maintained, the navigation posts were not in evidence until approaching the outskirts of Gt Yarmouth.  Headroom at Potter Heigham bridge at low water was normally over 7ft4”  We as a family regularly took Broom Admirals through PHB up to the late 70’s and other craft into the late 80’s, the Pilots were busy chaps back then

Then The Broads Authority was formed in 1989

The cranes stationed on the banks on standby were removed, never to be seen again.  The navigational posts on the river Bure now stretch further upstream than they ever have, they have also been moved further towards the middle of the river away from the banks, navigational floating marker buoys have also been added even further upstream to warn of shallow water.  The whole length of moorings in Gt Yarmouth home of the former hire craft yard are now out of bounds due to silting.  Potter Heigham bridge rarely sees headroom at Low water of 6ft 6” nowadays and 6ft 8” is rare indeed. There are hundreds and hundreds of both hire and private craft that can no longer transit PHB, these craft were designed to pass under PHB and up to the late eighties did so with ease.   The Broads Authority when challenged, on the rare occasion that they do respond is with their standard answer that this is due to climate change / global warming and that sea levels in the North sea have risen. By over eight inches really?  No of course they haven’t.

It comes as no surprise that average airdraft clearances at both Ludham and Wroxham bridges are now too decreasing year on year.

To add to the lack of dredging and maintenance on the whole of Lower Bure, the Broads Authority have also allowed a section of the river bed to silt up to dangerously shallow depths over a distance of about 100yds.  This has become known as the ‘Bure Hump’  Many of us with depth sounder / fish finders and the like have seen and recorded depths in the middle of the navigation down to as little as 2ft at low water.  The Broads Authority of course deny the existence of any ‘Bure Hump’  However it is there seen and noted by many.

During a flood tide, mother nature will push flood water into the Broads system, this is of course normal.  However now that the lower Bure is much shallower and narrower it cannot accommodate the same volume of flood tide water that it historically coped with.  That same volume of flood water has to go somewhere, it of course does just that, the volume of flood water goes further upstream over topping and flooding many areas

During the ebb cycle because the Lower Bure is now seriously silted up right down to the Yellow Post at the confluence with the river Yare and the afore mentioned Bure ‘Hump’ the water is held back and slowed down from draining out to sea.  The water levels are prevented from achieving a true historical  ‘Low Water Level’  before the next flood tide arrives.  This has been occurring and getting progressively worse for years now.  This then keeps the water levels throughout the whole of the northern broads progressively higher than they have been since the late 80’s.  This benefits the Broads authority as it negates them having to dredge many areas of the northern broads.  For years now have got away with dredging only small areas only when they absolutely have to.

While I’m on the subject of dredging, the Broads Authority recently released figures for their recent dredging operation for the last year – 26’000 cubic metres.  Sounds a lot doesn’t it?  In reality it’s a miniscule amount for the system.  Lets put that 26’000 cubic metres into context.  A dredging programme of 1m deep, 26m wide = just one kilometre length and that is it.  There are 200 kilometres (125 miles) of navigable waterways within the Norfolk and Suffolk broads (Nowadays many of us can no longer access a large percentage of that total).   One kilometre of dredging from a potential 200 kilometres over a whole year?  Yes, the Broads Authority have got an impressive amount of dredging completed haven’t they? And just how much of that 26’000 cubic metres was water?

Sometimes Broadland has to cope with a ‘Perfect Storm’ that is exceptional rainfall, Spring tides, Low pressure and the ‘Big One’ a north or north easterly wind.  When these features combine the rivers flood and the flood waters become ‘Locked In’– quite normal.  What is far from normal is the inability for the Bure to cope with and drain out the increased volume of water during the ebb tide cycle due to the afore mentioned factors.  This means it can take days or even weeks for water levels to return to what is now ‘Normal’

Here’s a simple experiment you can carry out yourself:-

Your bath is now the Northern Broads.  The plug is the silted lower Bure along with the Bure hump

Your taps are the flood tide (Timed) Put the plug in place in your bath.  Using a stopwatch run both taps and time how long it takes to fill the bath up to the overflow with both taps turned fully open – Note A

Now pull the plug fully out and time how long it takes to empty the bath – Note B

Fill the bath up to overflow again.  This time remove the plug only half way for the time of ‘B’ then put the plug back in.  Turn on the taps fully for timed ‘A’ – your bath is going to overflow, keep repeating the cycle but each time remove the plug slightly less, and soon your whole bathroom will be flooded.  Rocket science it is not

The above is the situation where we have arrived at since 1989 or it was until –

The Broads authority recently announced that they were no longer going to maintain depth to 12ft at low water throughout Breydon and the Yare as it was no longer considered a commercial waterway.  There apparently is now a sand bar across Breydon ( I have not seen or recorded this).  We should be asking ourselves how much more water is now going up the Bure due to the capacity of Breydon and the Yare being reduced?

The Second river crossing at Gt Yarmouth – The bridge abutments have reduced the rivers width by a full third (Not marginally as some clowns have stated). This is not helping the ebb tides one iota either

Since the Broads rivers became a commercial waterway – Wherries and the like then later a popular holiday and relaxation destination the rivers ability to cope with navigation has been fine for hundreds of years.  Potter Heigham bridge was a delight to transit to the wonders of the upper Thurne system

So just how have we ended up with the current situation in just thirty four short years?

Draw your own conclusions.

Btw - The Blessed Authority has been operating for thirty four long years now too

Griff

 

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1 hour ago, BroadAmbition said:

 

The Broads authority recently announced that they were no longer going to maintain depth to 12ft at low water throughout Breydon and the Yare as it was no longer considered a commercial waterway. 

 

By whom other than the BA

Apart from the science as explained by Griff, what is the criteria by which the status of "commercial waterway" is measured? What would be the minimum requirement? If we paid someone to transport a bag of coal from Yarmouth to Norwich and back once a year? Anyone know anyone who owns a coaster? :default_coat:

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If Breydon and the river Yare is no longer considered a commercial waterway then the Port of Norwich presumably in their definition no longer exists as a port. 

How does this reflect on the Broads Authorities position with regard to the the rail bridge which crosses the river at Trowse  and of course Carrow Bridge with regard to navigation rights?

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We have to remember that BA are not responsible for dredging for drainage purposes only for Navigation It is the Environment Agency who are responsible. The Inland Drainage Boards ( funded by Local Authorities ) pump the water from the fields & marshes The large grabs of the past were in the Anglian Water then Environment Agency yards. All went in re-structuring & are now hired when needed.

Probably needs getting our friendly MPs on the case again?

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Bytheriver - You make a fair point - BUT - if the Blessed Authority had kept the Lower Bure clear for navigation to the same state it was in when they inherited it when they were formed - It naturally follows on that drainage wouldn't be restricted to the state and levels we see nowadays

 

All went in re-structuring & are now hired when needed.

I could make a very easy argument that they are needed right now and for the foreseeable 

Griff

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2 hours ago, Bytheriver said:

We have to remember that BA are not responsible for dredging for drainage purposes only for Navigation It is the Environment Agency who are responsible. The Inland Drainage Boards ( funded by Local Authorities ) pump the water from the fields & marshes The large grabs of the past were in the Anglian Water then Environment Agency yards. All went in re-structuring & are now hired when needed.

Probably needs getting our friendly MPs on the case again?

God forbid the BA would want to take on  responsibility for anything that actually matters to users of the Broads and Local Residents.    It would mean less spending in all the other irrelevant areas they have got involved in! 

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On 09/05/2023 at 11:05, LizG said:

There is an old crossing at Stokesby, catches out yachts in the 3RRs as it the water is quite shallow by the old building.  If you look at the BA depth map you see a short spur from the footpath along the bank dead opposite where the crossing was.  I thought the crossing was more obvious but if you zoom in you can see it is shallower there

https://www.broads-authority.gov.uk/__data/assets/pdf_file/0026/180737/DEPTH__Stokesby-Reach.pdf

Here

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2 minutes ago, batrabill said:

It’s not very obvious is it? Looking up and down the river there seem to be lots of other places the same depth. What makes it special?

The shallows at Stokesby are an old cattle swim with a hard gravel bottom.  The same effect as at Runham Swim and Mautby Swim.  They may be shallows but they have been there for centuries.  I doubt if they form part of the present problems.

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to be honest i think its a sandbar that moves around the system in the lower Bure, we were watching the depth sounder as we went along the river before low tide and just about half a mile past scare gap as we headed for Great Yarmouth we were in the middle of the river and the depth readings suddenly shallowed down to about 2'6", it wasnt a long stretch, maybe a few boat lengths, just about where the first posts start appearing on the river, indeed if you look on what 3 words at ///drop.warns.memo , you can see the sand bars from each side restricting the channel to about 1/3 of the river width and almost joining in the middle of the river (put the satellite view on in W3W)

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14 minutes ago, grendel said:

how long before someone decides that only 6" deep is enough for paddle boards and they dont need to dredge deeper for boats?

Glad you agree - I have been saying this for a long time.  They don't need free made up moorings, either.

Trouble is, I fear that this may be nearer to the truth than we realise.

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21 minutes ago, grendel said:

the river before low tide and just about half a mile past scare gap

I was thinking about Scaregap farm myself, as this is where the river bends sharply left and heads back northwards again.  It is quite possible that this bend is, in itself, a constriction, as it is very shallow on the inside of the bend.  This will slow down the flow so that the water drops its alluvial silt in the reach just after the bend.  As the next bend is to the right, the main current will be spread across the width and the silt will form in the centre of the river and not to one side.

It's not rocket science!

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