Topic: Potter Heigham Bridge Height Calculator

Strowager    -- Jan-6-2013 @ 9:17 AM
  I thought it best to post this as a new thread since the one that it came up on was already off-topic.

Palmtree kindly took a set of three photos of the gauges at Potter bridge yesterday morning to enable their differing readings to be compared.

I've created a composite of the three gauges, (upstream, downstream, and pilot office), and added the daily graph from the EA flood gauge at Repps, about half a mile downstream.

That graph is uploaded to the Internet each morning at 04:30 to

This means that anyone interested in knowing how the clearance is going at Potter can check what the onsite gauges were showing the previous day by applying the conversion factors.

[Thread made sticky]

This message was edited by Richard on Jan-7-13 @ 2:40 PM

CaptBryan    -- Jan-6-2013 @ 10:04 AM
  Excellent bit of creative work, many thanks.

Captain Howe.
The Broads are:-
Not a Theme Park. Please leave them as you would wish to find them.

Paladine    -- Jan-6-2013 @ 10:33 AM
That's very useful, Strowager. Thank you for your efforts.

Using your formula, I now know I want 0.3 on the EA gauge, as I need 6'8" if the pilot's taking me through (a teensy weeny bit more if I'm piloting myself, 'cos I'm a wimp!).

palmtree    -- Jan-6-2013 @ 1:56 PM

Nice job on the calculator, just one thing the level indicator in the office is it showing 5'10" or 5'8"?


Strowager    -- Jan-6-2013 @ 3:28 PM
  quote:" just one thing the level indicator in the office is it showing 5'10" or 5'8"?"

You gave me quite a sinking feeling there Ian.  Wink

The Pilot's office gauge appears to be graduated in one inch increments, with a broader dash every three  inches, and a number every foot.

The numbers increment downwards, because the lower the float the higher the air clearance number.

The pointer is on the second division above six, hence the five foot ten inch reading.

(and I'm very relieved that I'd got it right ! Smile  )

This message was edited by Strowager on Jan-6-13 @ 3:30 PM

palmtree    -- Jan-6-2013 @ 3:50 PM

Sorry for the panic, now I can see the full scale it makes sense!


Richard    -- Jan-7-2013 @ 2:40 PM
  That is really brilliant, well done Strowger! I'm going to make this thread sticky.

Strowager    -- Jan-7-2013 @ 3:00 PM
  Thanks Richard, it should now enable anyone to satisfy their own curiosity of how the air clearance is doing at Potter.

A great idea of Palmtree to take that set of photos.

jitterbug    -- Mar-18-2013 @ 12:24 PM
  Hi everyone,

Quick question to find out what the water levels are like in horning and potter heigham area? We are in cambridgeshire and with the high rainfall our rivers have escaped their banks!

We are hoping to move our yacht from ferry marina to its new berth at hickling this friday and wanted a bit of insight in to how levels are there, will save us a journey if potter bridge not "dooable!"


Yacht Jitterbug

londonrascal    -- Mar-18-2013 @ 2:21 PM
  I think I am right in saying that if you look at the photo attached to the first post in this thread, you use the calculations from the Environment Agency's water level gauge (web link in first post also) and by applying the formula get the river level at Potter Heigham Bridge - meaning you need not be at Potter Heigham or see the gauge at the bridge/pilots office to get an idea of the air draft.

|  Robin  |

Norfolk Broads LIVE!
Captain's Blog Video Series

Siddy    -- Mar-18-2013 @ 9:00 PM
  On 16th it was showing 5'2" at the bridge blowing a gale, water over the bank on the free grass moorings on the right and we got on moorings near bridge office.
Today at 1200 it had dropped 4" and like a mill pond.


FishersHaven    -- Feb-10-2015 @ 9:09 AM
  I thought this thread deserved a bump, found for me by expilot as a perfect answer to my question.

We love the Broads

Jeremy-Aslan    -- Feb-10-2015 @ 4:13 PM
  The clear info from Strow at the beginning of this thread is very useful.

Another way of calculating the same result, which I find easier, is as follows:

Google 'Environment Repps' and the first hit is the reading up to 4am that morning at Repps

From that trace, figure out what the height will be at the time you want to go through TODAY.

Then, 0.5m = 6ft clearance (as per Pilot Office Gauge).  Work out how many cm 'better' than 0.5m it is, then convert to inches (where 2.5cm = 1 inch, roughly), and it's that  many inches greater than 6ft.  I.E., 0.35m is 15cm better than 0.5, so 6in better than 6ft, = 6ft 6in.

'We demand rigidly defined areas of doubt and uncertainty' (HHGG)

wombat1    -- Feb-11-2015 @ 7:08 AM
  Boy am I glad I know we cant get underneath! Confused


Limbury1    -- Feb-11-2015 @ 2:50 PM
  Me too, my problem is ludham bridge im nervous about it.last time I was there I couldn't get under according to the measurements so aborted it .So I've got to get up courage and try I need 8ft 6ins to scrape under.

Limbury 1
If you can't see it it's not there ,if you
can see it , it's still not there,the world
is all Illusion.

palmtree    -- Feb-11-2015 @ 7:02 PM
  If the Reps height gauge falls to zero, that is about 7'7" clearance. Has this ever been seen at potter?


ADI    -- Feb-11-2015 @ 7:57 PM
  someone pulled out the plug on 11 February 2012 see attached photo, I had never seen the boat so low in the water i thought it was half sunk.


Adrian, Michelle, Beck and Braydon,
the crew of FERZAN.

annville    -- Feb-12-2015 @ 12:16 PM
  Hi Limbury 1 My previous boat needed 8ft 6inches i found that if it was close, i had a height pole on front of boat,  if you edge under in centra then push throttle full open the screw digs the water out from under the boat the boat drops noticeable giving more air gap then momentum kicks in and then your through, you need to compensate on rudder for any side ways movement of stern, I had twin engines so it made it easy for me, often thought that may be one of the reasons in addition to directional stability Pilots go through bridges on full throttle John

Limbury1    -- Feb-12-2015 @ 5:17 PM
  I've got twins but ihad a height mishap two years ago on a lock guillotine of which I'd been under loads of times cost £5000 so now if it's tight I'm nervous.

Limbury 1
If you can't see it it's not there ,if you
can see it , it's still not there,the world
is all Illusion.

dannyboy    -- Mar-20-2015 @ 7:55 PM
  James May tells me the clearance at PH has been about 7' recently as water levels are very low... has anyone seen it this week?


'In Caelis et in aqua'  

Jeremy-Aslan    -- Mar-20-2015 @ 8:44 PM
  Yup  -  water level really low, so loads of bridge clearance.

On Sunday evening, more than half way from low to high tide, there was 6ft 9in.

Looking at the Repps gauge for today (Fri), there was 7ft at 0400 (and presumably at 4pm as well).

But also means that some of the normally-navigable rivers are a bit shallower than they might be sometimes.  -  like I went really firmly aground on Hickling on Sunday.

'We demand rigidly defined areas of doubt and uncertainty' (HHGG)

boat-mad    -- Mar-21-2015 @ 1:20 PM
  I recently compiled a chart to get a rough idea of clearances at Potter Heigham Bridge.

Using B.A tide information I look for dates that high or low water occurs near 00:30 Hours at Gorleston (Yarmouth Bar) adding on four hours for high and low water at Potter Heigham makes the time 04:30 Hours which is the time that the Environment Agency tend to record the river level at Repps.

I then use Strowager’s formula to work out the Bridge clearance.

This is what I have done so far.

16 February 2015 – 9 mins before Low Water 7ft 1in (0.18 at Reps)
24 February 2015 – High Water 6ft 1in (0.48 at Reps)
01 March 2015 – 29 mins before Low Water 6ft 8in (0.30 at Reps)
12 March 2015 – 6 mins before High Water 6ft 9in (0.28 at Reps)
18 March 2015 – 25 mins after Low Water 7ft 2in (0.14 at Reps)

I hope I’ve done it right. Question

Wouldn’t it be good if there was a permanent webcam to The Pilot’s gauge?

Kind Regards

dannyboy    -- Mar-23-2015 @ 6:46 PM
  We went up to check the boat on Saturday and it was firmly stuck in the cutting! Very low... Good job I wasn't planning a sail in a hurry!


'In Caelis et in aqua'  

grandpamike    -- Jun-12-2016 @ 1:58 PM
  Thanks for a very useful thread. Richard, the link to the Repps gauge in your sticky posted back in 2013 is now superseded. Here's the current one:

Repps River Level

Grandpa Mike

Dreamweaving    -- Oct-20-2016 @ 6:20 PM
  With all these measurements flying about, can anyone tell me how the measurements are taken....
I know the water surface is where the measurement is taken from... LOL

Where is the second on an ARCHED bridge?... As I don't know of any boats with an arched top, matching the profile of the bridge's stone work...

hazel    -- Oct-23-2016 @ 9:16 AM
  just to let you know we actually managed to get through the bridge on OCT 8th we were on Southern Horizon height 6ft6 the pilot got ud through even though the clearance was just showing slightly over that height we were almost alone very few boats therefor 4 nights cane back through 12th low water was at 430 but we got through no problem at 1240 it was a neep tide and the young pilot was taking boats through ar 6ft7 or less

Dreamweaving    -- Oct-25-2016 @ 12:40 AM
  I'm informed that the bridge height displayed in the Pilots office is taken from a width of 6 foot and the marker by the bridge has been hit by boats so many times its not to be relied upon...

ADI    -- Aug-11-2019 @ 11:04 AM
  Does anyone know if this formula still works, I have a feeling the site datum has changed since this was worked out.


Adrian  Michelle

Beck  Braydon and Mere.

ADI    -- Sep-23-2019 @ 9:48 PM
  Thought i would add this as i thing the thread it was on was lost during site issues.


Adrian  Michelle

Beck  Braydon and Mere.

vipergreen    -- Aug-21-2020 @ 6:52 PM
  I have hired a 6’6’” boat mid September what’s the chances of getting under Potter Heigham bridge ?

Jeremy-Aslan    -- Aug-21-2020 @ 10:20 PM
  6ft 6in  -  possible, but optimistic.  If it were 6ft 3n, you'd have a much better chance.

You would definitely have to be right on Low Water  -  soon after LW, the level goes up quite quickly.  You say 'mid September'  -  On Mon 14 Sep, LW is 17.15 at Potter, which is right at the end of the day for the Pilot, any later in the week, it's well after office hours, or rather early in the morning.

Have a look at the level for the gauge at Repps Here.

Or search online for 'Repps River Gauge'

Remember that 0.5m = 6ft clearance, so at the moment it is showing LW on 20-Aug 9pm as 0.3m  -  that's 20cm 'better' than 0.5, so a very tight 6ft 8in clearance  -  but also look how quickly it goes up, 6cm by 10pm;  it may not sound much, but that would crunch the top off a 6ft 6in boat!  Also, local knowledge may suggest that it goes up quicker at the bridge than a mile downstream where the gauge is.

You'll also see that the 'trend' is upward at the moment, the river level is 1 or 2cm higher each day than the day before  -  on the 16th it was 0.22m = 28cm better than 0.5 = 6ft 11in clearance, loads of room!

Check the levels AND the trend before you start your trip, to see if it's worth asking the pilot if you'll get through.

'We demand rigidly defined areas of doubt and uncertainty' (HHGG)

oldhirer    -- Aug-22-2020 @ 8:16 AM
  It depends where you have hired from. If hired from Martham you will probably get through.

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