Speed on rivers vs. canals

[Chalky]

As a boater who spends all of their time on canals I have a question about boat speed and enforcement on rivers.

On a canal with "stationary" water 4 mph through the water is the same as the speed over ground.

On a river with moving water this isn't the same. If the river is flowing at 4 mph and I'm doing 4 mph into the flow then my speed though water is 4 mph however my speed over ground is 0 mph. If I'm going down river and I'm going at 4 mph through the water I'm going at 8 mph over ground.

 

Where I'm puzzled / confused is this.

For arguments sake lets assume the river has a speed limit of 4 mph and that I need to maintain a headway of 2 mph to maintain steerage.

If the river is flowing at 4 mph and I need to maintain 2 mph to be in control I'm doing 6 mph over ground and 2 mph through the water. How does this relate to the speed limit. Am I speeding or not?

What do they do on rivers like the Thames, Avon, Trent etc where they can have fast currents?

[bottle]

River speeds are (I believe) 8 mph down stream and 6 mph upstream, I also believe that this over the ground.

 

Having said that you need to be going fast enough (engine speed) to maintain steerage.

[OldGoat]

As a boater who spends all of their time on canals I have a question about boat speed and enforcement on rivers.

On a canal with "stationary" water 4 mph through the water is the same as the speed over ground.

On a river with moving water this isn't the same. If the river is flowing at 4 mph and I'm doing 4 mph into the flow then my speed though water is 4 mph however my speed over ground is 0 mph. If I'm going down river and I'm going at 4 mph through the water I'm going at 8 mph over ground.

 

Where I'm puzzled / confused is this.

For arguments sake lets assume the river has a speed limit of 4 mph and that I need to maintain a headway of 2 mph to maintain steerage.

If the river is flowing at 4 mph and I need to maintain 2 mph to be in control I'm doing 6 mph over ground and 2 mph through the water. How does this relate to the speed limit. Am I speeding or not?

What do they do on rivers like the Thames, Avon, Trent etc where they can have fast currents?

 

 

Yes, you are. certainly on the Thames where the rule is 'over the river bed'.

Logically daft, but how can you expect an enforcement officer (practically) to measure your speed over the water - he'll most likely be on land.

Bottle's rule above is more logical - but that's not on the Thames.

 

In practice the EA are mostly concerned about wash and disturbance to the infrastructure - so a NB is most unlikely to get pulled over. (that wasn't the question).

[gazza]

River speeds are (I believe) 8 mph down stream and 6 mph upstream, I also believe that this over the ground.

 

Having said that you need to be going fast enough (engine speed) to maintain steerage.

The Nene and Great Ouse are (mostly) 7mph in either direction.

The Old Nene is 5mph or 4mph.

The tidal sections of the Nene and Ouse are unrestricted.

The Cam is as the Nene and Great Ouse

The 100' is unrestricted

 

That scratches the surface in East Anglia

 

So the answer is, check the waterway you are on....

Edited April 30, 2015 by gazza

[Timleech]

River speeds are (I believe) 8 mph down stream and 6 mph upstream, I also believe that this over the ground.

 

Having said that you need to be going fast enough (engine speed) to maintain steerage.

 

That's true for the Trent, but others have the same limit either way (eg Weaver, Witham 6mph).

 

Tim

[nicknorman]

In fact speed limits on rivers vary according to which river. Rivers that remain navigable when there is a strong current or tide tend to have higher limits, but for example on the non-tidal Thames it is 5 mph but you are unlikely to have more than a couple of mph current, and normally less than that.

[Paul C]

Is there a general speed limit for rivers? For example, the Caldon Canal joins and leaves the River Churnet at one point, is the speed limit on this section 4mph or 6mph?

 

Anyway, to answer the original question and to agree with others who have already posted: some rivers have a different upstream/downstream speed limit. These are rivers where there may be a not-insignificant flow. Some rivers have the same limit, and these tend to be those with insignificant flow, eg River Weaver.

 

Pragmatically, there are not many canals where 4mph speed limit is achievable - you could try, but would end up creating a large wash and wasting diesel while tending towards (but never reaching) around the limit, on many sections of canal.

[Timleech]

Is there a general speed limit for rivers? For example, the Caldon Canal joins and leaves the River Churnet at one point, is the speed limit on this section 4mph or 6mph?

 

 

No, I'd be surprised if the limit on the Churnet isn't 4mph. Same on river sections of the Calder & Hebble, I think there it's 4mph, although below Wakefield (Technically Aire & Calder but the same river) it's 6mph.

 

Tim

[keble]

The Severn is 6 up and 8 down.

Maintaining steerage while coming downstream is a problem. I read somewhere that commercial boats would come down the Severn backwards when approaching Gloucester lock. That's pretty scary as there's lots of bends in the last mile or two!

[Cheshire cat]

Trying to do 4mph more than a 4mph current is pretty scary in a narrowboat. At some point you've got to grit your teeth and try to do 180 degree turn without hitting anything.

[Rob L]

A quick search on t'internet reveals the answer as given above by nicknorman. -

Speed limit varies depending on the river in question and depending on the expected flow. Speed is measured 'over the river bed'.

Low flow sections have a low speed limit, often 4 or 5mph, and generally the same in either direction. High flow sections have higher limits, typically higher downstream than upstream. For example, the Avon; 6mph downstream and 4mph upstream. This caters for the higher speed over the river bed (being an aviator, I'd call it groundspeed), when motoring downstream. Tidal sections on some rivers are significantly higher limits, e.g. 15mph on the Great Ouse.

 

I guess the significant point here is that you should check before you go. EA website has information on the rivers under their juristriction, and others are only a Google search away. Be aware of strong stream advice too. I learned a sobering lesson about that last year on the Stour!

[Mike Todd]

River speeds are (I believe) 8 mph down stream and 6 mph upstream, I also believe that this over the ground.

 

Having said that you need to be going fast enough (engine speed) to maintain steerage.

I doubt if there are many boats (if any) who can **measure** their speed through the water.

[Timleech]

I doubt if there are many boats (if any) who can **measure** their speed through the water.

 

 

Plenty of lumpy water boats have that facility, agreed you won't find many on the inland waterways. Also such readings would be meaningless if the channel is in any way restricted.

 

 

Tim

[Naughty Cal]

I doubt if there are many boats (if any) who can **measure** their speed through the water.

We can.

 

We have a speed through water and a speed over ground. Speed through water is measured by the Raymarine Tri Data which has sensors built into the hull and speed over ground is measured by the chartplotter via GPS.

 

The difference between the two being the current at the time.

[pearley]

The Nene and Great Ouse are (mostly) 7mph in either direction.

The Old Nene is 5mph or 4mph.

The tidal sections of the Nene and Ouse are unrestricted.

The Cam is as the Nene and Great Ouse

The 100' is unrestricted

That scratches the surface in East Anglia

So the answer is, check the waterway you are on....

Just come down the flood relief channel. Nice to be able to open the throttle, especially after the shallow Well Creek.

[gazza]

Just come down the flood relief channel. Nice to be able to open the throttle, especially after the shallow Well Creek.

 

Well Creek, my love hate area, love the vista, hate the lack of depth

 

I like it up the Relief Channel, its peaceful up the top at Wigenhall St Mary, Downham is handy for shopping etc - enjoy!

 

We are hopng to spend spring bank holiday week up the top end of the Ouse.