River levels; other inland waterways

[Golden Time]

Looking at the EA website the level has started to fall.
Let's hope for no more significant rain for the rest of the week.

It's a shame the marina didn't slacken the ropes on the boat that has sunk. Looking at the picture I think it is moored quite close to the marina office ?

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I really struggle to understand the EA website for river levels. For example it says that the river level on the 24th was 0.32m. How is that possible? No boat could go through with a river depth of 32cm?

It was strange to see all 3 sluice gates open and at the same time silence. Normally one gate is open about 6" and you get a thunderous roar of water going through.

I don't know the situation around the sunk boat - things began to get heated just after I had arrived to check on mine. But, the Harbourmaster appears to have slackened ropes throughout the Marina - mine were definitely more slack today than 2 days ago.

The boat in question I think is a live aboard and doesn't appear to have moved in a long time. I think the problem was compounded by the fact that that pontoon is the only one where you step down from the pavement and possibly because the Harbourmaster isn't there all the time and it was maybe expected that the guy was on board so would deal with it. I wish we could log in to see webcams for a glance at the conditions.

 

[teddington_lock]

Hi Golden Time

The 0.32 is a measurement above a level of water called 'headwater' which is basically zero.

Not zero as in zero water in the river , but a fictional line in the river that levels are worked out from. Bridge heights , for example are worked out from headwater , so if the bridge is 10 feet 0 inches and the reach is running at 4A , then really you only have 9 feet 8 inches air draft.

The thames locks have a mandate to keep levels within three inches of headwater either way , so you would hear thames lockies talking of 'three above' or 'three below' ( headwater ) .

So your reading of 0.32 is metric ( 0.025 equates to 1 inch ) , and converts very roughly to 13A ( 13 inches above headwater ) , what does the chart say is your normal range ?

 

[david_bagshaw]

It was strange to see all 3 sluice gates open and at the same time silence. Normally one gate is open about 6" and you get a thunderous roar of water going through.


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The way to think of this is :-

imagine the river was syrup, and the rive bed was a large turkey oven tray


The river bed is slightly sloped, and the upper edge of the tray represent the weir.

if you tip the syrup slowly on the edge it runs to the bottom an makes a slow layer that flow away, ie the big drop with one weir section open.

if there is a lot of syrup, it cant flow way quickly enough, so the level in the pan rises. (I am asuming it hasnt reached the other end)

Same with the river, with the gates fully open the flow cant clear, so the level rises in the lower reach.


As the lower reach is higher, the water flow doesnt look as impresive.

I am trying to find a picture of the navagable weir at Driel in Netherlands, that gets fully opened and all traffic goes under the weir.

 

[Golden Time]

Hi Golden Time

The 0.32 is a measurement above a level of water called 'headwater' which is basically zero.

So your reading of 0.32 is metric ( 0.025 equates to 1 inch ) , and converts very roughly to 13A ( 13 inches above headwater ) , what does the chart say is your normal range ?

http://www.environment-agency.gov.uk/homeandleisure/floods/riverlevels/120736.aspx?stationId=6045

So for this site at Stamp End, the site datum is 3.42m and the current level is 1.0m. So does that mean that 3.42m is the "headwater" and the river is 1m above the headwater. So the river is 4.42m deep, roughly?

 

[teddington_lock]

No , AOD is Above Ordnance Datum (3.48) which is the height above sea level that he headwater line is set at , does that make sense ?

You need to look at the 1.00m reading , which looking at the normal range seems to be about right , about 36A

You have to remember that these readings are taken from a level in a known depth of water , sometimes a lock sill. The depth of the water in the rest of he reach can vary considerably due to uneven bottom contours.

To show what I mean , this is our reading at Tedders this morning at 0630

http://www.environment-agency.gov.uk/homeandleisure/floods/riverlevels/136483.aspx?stationId=7268

It shows our AOD as 4.38 which is the height of the headwater in the reach above the lock above sea level , you will see that we are running at 0.02 which is basically headwater, 0.00 is HW

 

[Golden Time]

No , AOD is Above Ordnance Datum (3.48) which is the height above sea level that he headwater line is set at , does that make sense ?

You need to look at the 1.00m reading , which looking at the normal range seems to be about right , about 36A

You have to remember that these readings are taken from a level in a known depth of water , sometimes a lock sill. The depth of the water in the rest of he reach can vary considerably due to uneven bottom contours.

To show what I mean , this is our reading at Tedders this morning at 0630

http://www.environment-agency.gov.uk/homeandleisure/floods/riverlevels/136483.aspx?stationId=7268

It shows our AOD as 4.38 which is the height of the headwater in the reach above the lock above sea level , you will see that we are running at 0.02 which is basically headwater, 0.00 is HW

To make it a little more simple,

If I have a bucket and I make a mark about half way up the bucket. Then I tip in an unknown quantity of water. Headwater is the equivalent of the mark in the bucket. I would then measure the depth to the mark in order to get the equivalent of the readings EA publish? I can't measure straight to the bottom of the bucket because it has a bunch of rocks and no two measurements would be the same.

The EA doesn't tell you the depth of the river, it tells you how high above a fictional "mark" at the measuring station the water currently is.

Have I got it now? LoL.

 

[mikemanor]

The EA doesn't tell you the depth of the river, it tells you how high above a fictional "mark" at the measuring station the water currently is.
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Exactly, which is why here in the Anglian Region the Waterways team are always at pains to point out to us that the EA River Level website is intended for flood defence use, not navigation, and that the data shown bears no resemblance to the navigable state of the River Great Ouse!!

 

[Brayman]

Exactly, which is why here in the Anglian Region the Waterways team are always at pains to point out to us that the EA River Level website is intended for flood defence use, not navigation, and that the data shown bears no resemblance to the navigable state of the river!!

Except where it comes to low bridges, eg on the Thames at Cookham the data is very useful to help determine how easy/difficult/impossible it will be to get through.

 

[teddington_lock]

To make it a little more simple,

If I have a bucket and I make a mark about half way up the bucket. Then I tip in an unknown quantity of water. Headwater is the equivalent of the mark in the bucket. I would then measure the depth to the mark in order to get the equivalent of the readings EA publish? I can't measure straight to the bottom of the bucket because it has a bunch of rocks and no two measurements would be the same.

The EA doesn't tell you the depth of the river, it tells you how high above a fictional "mark" at the measuring station the water currently is.

Have I got it now? LoL.

Sorry , I was trying to help , I'm not attempting to mock you.

Merely trying to explain how it works.

 

[Golden Time]

Sorry , I was trying to help , I'm not attempting to mock you.

Merely trying to explain how it works.

In no way did I think you were trying to mock me. With your explanation I formulated my bucket analogy to take out the variables between our two locations and make a generalisation. Now I understand how it works. The AOD thing that you explained is essentially what level above sea level that my "mark" in the bucket is.

Exactly, which is why here in the Anglian Region the Waterways team are always at pains to point out to us that the EA River Level website is intended for flood defence use, not navigation, and that the data shown bears no resemblance to the navigable state of the river!!

Thanks, now I understand it. To be honest I never understood it before and so I never used it for navigation anyway.

I think it does bear some resemblance to the navigable state of the river. For example, the controlled navigation between the Brayford Pool and Stamp End Lock is based entirely on the river level (according to C&RT). What C&RT don't know though is what levels activate the red light and subsequently the flashing red light because that is EA's domain and I haven't asked them yet. There is no online way to see the green/red/flashing state of this stretch of navigation. The river level will indicate whether that stretch is open, caution required or closed.

 

[Momac]

A couple of pictures of the River Trent

This one is outside the Bromley Arms pub at Fiskerton. Anyone who knows it will understand just how high the water is.


And an aerial shot of Newark

 

[CJL]

Thames unsafe for boaters - icebergs expected!

http://www.bbc.co.uk/weather/2636534

 

[macnorton]

Orton lock

 

[macnorton]

Jones marina webcam (River Ouse)

http://www.jonesboatyard.co.uk/webcam.aspx

 

[Golden Time]

Just as an update... The Brayford Pool is now back to normal levels and the sunk boat has been successfully refloated. I still don't know what happened, but there is no damage to the hull that I could see today so I'm assuming it was tied too tight and got pulled under.

River Witham downstream of the lock/weir remains at the same level as upstream but I suspect the sluice gates will start closing soon before the Brayford starts dropping too low. Can't understand the EA river data though because its now reading that the water is lower than "typical" and it certainly isn't. LoL.

 

[SimonA]

Tried to get down to Buckden Marina on the Great Ouse today and the Buckden to Offord road was under water. Watched a van go through and decided the water level was too high to risk it in a car.

 

[JClarkes]

The River Shannon in Ireland can become very flooded down near Portuma, I have not been down this year but would be interested to see how the banks are holding up

 

[No Regrets]

The River Shannon in Ireland can become very flooded down near Portuma, I have not been done this year but would be interested to see how the banks are holding up

Lake Shannon you mean?

 

[boatone]

......I have not been done this year .....

Join the club, mate !

 

[JClarkes]

Join the club, mate !

Thanks, edited.