Bridge Clearance Gauge Boards

[NotDeadYet]

How reliable/accurate are the gauge boards at the vertically challenged bridges?  I ask because, thanks to https://www.barnesbrinkcraft.co.uk/webcam/ I've been keeping an eye on the one at Wroxham and have yet to see more than 6'9" and that just once, very close to low tide.  The B.A. published Average High Tide clearance in summer is 7'3", presumably at the centre of any arch.  I guess there may be more water feeding in right now, and the recent prevailing winds may be having an impact, plus generally low pressure, but 6" difference at different tide heights seems a bit large.  

Obviously, I have time on my hands!

 

[RS2021]

If you want to know how much higher than normal the river levels are and have time on your hands you can get a lot of data here: -

https://riverlevels.uk/river-bure-hoveton-hoveton-broad-tidal#.YHcUrKySmUk

This is the nearest EA gauge to Wroxham Bridge and if you scroll down the page you get a button 'Download Long Term Data as CSV'. This will give you daily data back to 2012. All you then need is to know how this relates to the gauge at Wroxham Bridge...

[CambridgeCabby]

The new board upstream of Ludham is near as dammit 3inches out , I need 8ft and we had approx three inches to spare , the downstream board is about 3.5inches out 

[Guest]

We went under Wroxham bridge today showing just over 6ft 6in, we are 6ft 10in and we had maybe 6in to spare...

[SwanR]

This conversation always makes me a little nervous. We wouldn’t want to give anyone, especially any new hirers reading the forum, the impression that they should take risks with the air draft of their boat vs the bridge height shown. 

Perhaps Tom @BroadsAuthority could comment on how these are maintained if he gets a chance. 

[grendel]

i measured ludham bridge last year and there is 8 ft of clearance if the two side lips are visible (a bit more on the right going downstream)but from the concrete lip on the left side heading downstream to the bridge at that side is 8 foot

 

[grendel]

that said there are a lot of factors that influence the water levels, the best clearances are usually in the summer months.

[NeilB]

I think you’d be lucky to see 7ft 3” at average low water at Wroxham bridge let alone high water!

[grendel]

I must be lucky as every time I have hired a boat i have got under potter heigham and wroxham bridges with no issues whatsoever, its just a matter of which boat you hire.

[RumPunch]

11 hours ago, grendel said:

I must be lucky as every time I have hired a boat i have got under potter heigham and wroxham bridges with no issues whatsoever, its just a matter of which boat you hire.

Or how heavy the crew are - want to reconsider the excercise regime, Grendel ?

[TheQ]

I think the BA will measure a bridge , find the absolute lowest point a boat might go under then take off a couple of inches for safety.

The boat yards will measure their boats air draft and add on 6 inches for safety..

 

And some still manage to hit the bridges...

[RS2021]

1 hour ago, TheQ said:

And some still manage to hit the bridges...

The problem is everyone knows the gauge is inaccurate and everyone knows the airdraft of the boat the yard gives you is inaccurate, you just don't now by how much. So you have to try the boat to see if it actually fits. This has been going on for so long now if the BA and the yards suddenly gave accurate information no one would believe it and even more boats would hit the bridges. All the privateers know what the gauge has to read to get their boat through. Again if the BA suddenly change it, many privateers would hit the bridges. Answer would have been to start with accurate information, but its too late for that now.

[SwanR]

Please be careful with this kind of post. There are a lot of people hiring for the first time this year or inexperienced and looking for advice. 

In my view it’s irresponsible that we should ever be encouraging anyone to ignore the bridge height markers or disregard the information given by their hire yard. 

 

[RS2021]

47 minutes ago, SwanR said:

Please be careful with this kind of post.

I agree. I think my post is more of a lament about the consequences of giving people poor information. I've always thought we should trust people with good information and advice.

My own experience is that if I had taken the river gauges and boat air draft at face value I would never have discovered and enjoyed the beautiful river Ant. I've also read reviews for the boat I hired and many hirers were disappointed that they could not get under Ludham bridge. I suspect most (not all) of those reviewers could have and simply turned back at the first gauge. Good information would have allowed them to have enjoyed their holiday more and maybe created new Broads enthusiasts, instead of leaving them disappointed. 

[CambridgeCabby]

To reiterate what I believe is the the sentiments in SwanR’s posting , if a hirers boat states the air draft of his boat is for example 8ft 2 then they should in no circumstances attempt to pass a bridge unless the marker board is displaying at least 8ft 2 (and remember to drop any higher superstructure , awnings , telly aerials etc) . Every season we see and hear of hire boats and indeed privateers “risking it” with the result at least being impact with the bridge causing damage to the boat or in more extreme cases injury , some serious, to someone on board .

Use the tide tables and time your passage for low water , speak to those with local knowledge certainly , but don’t ignore the information given to you by the boat yard or the marker boards .

Have a fun but safe holiday afloat 

[grendel]

Ask Ian what happens when you raise your head too soon at Ludham bridge, and that has a fairly smooth concrete structure. two of the really low bridges have pilots there to take you through, all hire boats should use them (some private boats do too) The only yard I know that dont advertise their boats Airdraft is Marthams, and by their rules, if they can get you under potter heigham bridge, then you are not going to be too high for any of the other bridges on the broads.

The boatyards and bridge pilots know what individual boats need to get through Wroxham and Potter Heigham, for the rest of the bridges, trust to the figures provided by the height gauges and boatyards, they will ensure you get through a bridge safely, some bridges the shape of the boat vs the shape of the bridge make a difference to the heights shown, dont forget the bridge height shown may not be measured at the highest point of the bridge, most are the height at a certain width that your average boat can clear. ditto the air draft of a boat may not be the height to the heighest point, its more the height needed to get the top corners of the roof to clear certain bridges, thus the heights may not accurately reflect the height of the boat, this is why i think people state that the gauges are wrong, or the boat airdraft is wrong, its because each is measured for specific bridge clearances. unless you know the parameters used to arrive at the figures, its best not to second guess the boat and bridge owners.

[Broads01]

3 hours ago, CambridgeCabby said:

To reiterate what I believe is the the sentiments in SwanR’s posting , if a hirers boat states the air draft of his boat is for example 8ft 2 then they should in no circumstances attempt to pass a bridge unless the marker board is displaying at least 8ft 2 (and remember to drop any higher superstructure , awnings , telly aerials etc) . Every season we see and hear of hire boats and indeed privateers “risking it” with the result at least being impact with the bridge causing damage to the boat or in more extreme cases injury , some serious, to someone on board .

Use the tide tables and time your passage for low water , speak to those with local knowledge certainly , but don’t ignore the information given to you by the boat yard or the marker boards .

Have a fun but safe holiday afloat 

I agree, however the only issue I have with that relates to Ludham. There, as those of us who know it know, the height boards are wildly inaccurate and also inconsistent with each other. How you would advise a new hirer in the Ludham situation I'm not sure. You could tell them to adhere strictly to the gauge but if they did that a big proportion of Richardsons boats wouldn't reach the Bure and others would never see the Ant when in reality they had a foot to spare.

[CambridgeCabby]

Re Ludham , the new board as you travel downstream is within half an inch of the upstream board on the approach , the posted airdraft on the helm of a hire boat (including Richardson’s) often has an allowance built in to allow for some bridges arches etc , I would recommend that a hirer if they are in doubt should moor up and ring the boat yard quoting the indicated height of the bridge and adhere to what the yard advises.

if the boards are showing sufficient clearance then no need to ring just pass under the bridge exercising due care .

We shouldn’t advise anyone to simply rely on the boards being wrong or the incorrect airdraft being posted onboard 

[SwanR]

1 hour ago, Broads01 said:

How you would advise a new hirer in the Ludham situation I'm not sure. You could tell them to adhere strictly to the gauge but if they did that a big proportion of Richardsons boats wouldn't reach the Bure and others would never see the Ant when in reality they had a foot to spare.

That is exactly what we have done three times - hired a fly bridge cruiser in October when the water levels were high and stayed on the northern Broads to the south of Ludham Bridge. Still plenty to see and do, just no point chancing whether we would get through and whether we would get back. 

[NotDeadYet]

I'm delighted that my simple question has aroused such an interesting and varied range of replies.  It's clear that the answer to my question is "not very" or, less kindly, "use your eyes and brain, and listen to the locals".  Excellent!

[Andrewcook]

As to Ludham Bridge  it all deepens on the weather Rain and Wind that does push the water level up considerably that's to bear this in mind including  Wroxham  Bridge as well .As for Potter Heigham if the weather. Stays good and the water stays low it's nice to get Under depending on what Craft you are on . 

[Broads01]

4 hours ago, Andrewcook said:

it's nice to get Under depending on what Craft you are on . 

It's very nice indeed but nowadays if you're hiring you really need to be on either a Martham's boat or a sailing boat.

[vanessan]

9 hours ago, Broads01 said:

It's very nice indeed but nowadays if you're hiring you really need to be on either a Martham's boat or a sailing boat.

Or in a coracle!

[annv]

as you approch slowly, If you can stand at back of boat look along the roof line at its highest point as you aproach the bridge if you can see the far under side of bridge on the under side you will get through if you cant see the far side you are to high so stop. John

[NotDeadYet]

5 hours ago, vanessan said:

15 hours ago, Broads01 said:

It's very nice indeed but nowadays if you're hiring you really need to be on either a Martham's boat or a sailing boat.

Or in a coracle!

..... I see a future in submarine hire!