Flood locks

[magpie patrick]

a bit of musing that's come out of some historical research I'm doing on the Boyne, but relates to most river navigations...

 

The Boyne has five flood locks but nine lock cut (excluding the 7 kilometre long canal from Stackallen) - in a way it's rather reminiscent of the Calder and Hebble, short and long lock cuts before becoming a separate canal for the uppermost few miles although unlike the C&H the Boyne has never had changes to the route. 

 

Anyway, the question is about flood locks, a feature on both navigations but thinking about it I'm not sure they're that common elsewhere - I haven't attempted a list of such structures so I don't know but I don't think there are any elsewhere in Ireland and there are only a few anywhere away from the Calder and Hebble/Aire and Calder in England.

 

So - I know why they're needed but why do some lock cuts not have them? It will clearly be related to whether floods in the lock cut cause a problem and that is often but not always a function of the length of the lock cut - the longer the cut  the more likely the downstream end is above ground level.  More importantly were they a feature of early river navigations or did it take the river engineer a while to latch on? Did longer lock cuts result in the need for flood locks, or were flood locks an innovation that set the engineer free to build longer cuts through areas more vulnerable to flooding? I guess the engineers would have understood mill leats where the leat can often but not always be cut off at the upstream end

 

This question is partly because I wonder of the ones on the Boyne, or the lower Boyne at least, were a hasty addition after first opening.... 

[Richard T]

The river Soar currently has three flood locks and the Trent one.

The one at Pillings on the Soar is at the upstream end of the long cut through Loughborough and it usually prevents the river from flowing down the cut and into the town. However in big floods the gates are overtopped and local flooding occurs at places such as Pillings Lock marina.

Kegworth flood lock is on a short cut, there must be an obstruction in the river bed as there is often a fall of 450mm at times of flood although when water levels are very high the gates are overtopped.

The one at Redhill was originally a full lock but when the river levels were changed in the 1970s it became a flood lock.

There are also flood gates on Zouch cut which protect the water levels on the cut and nearby properties.

There is a flood lock at Sawley, this is on the entrance to the cut and protects the levels on the cut. Again it can be overtopped.

There are flood gates at the entrance to Cranfleet Cut.

The EA have also instlled flood gates in Shardlow which work in connection with banks to prevent the village from flooding.

Examination of the drawings attached to the original canal acts may indicate if the flood locks were original or not.

[matty40s]

It seems strange to me that the Kegworth and RedHill ones are maintained, as they dont seem to provide protection for anything any more....I suppose maybe holding back some head of water at times but when the floods really come, they just get overtopped and the main river channel passes them by anyway.

[matty40s]

For example..

 

[TheBiscuits]

32 minutes ago, matty40s said:

It seems strange to me that the Kegworth and RedHill ones are maintained, as they dont seem to provide protection for anything any more....I suppose maybe holding back some head of water at times but when the floods really come, they just get overtopped and the main river channel passes them by anyway.

 

I suppose that's actually worse than not having them - people don't get to see the water rising fairly often in the usual range of the flood defences, and start to assume it won't flood.  If they saw it coming up to within a few inches of the top then subsiding again more often they would be much more aware that water levels change!

[pearley]

Richard T has forgotten the flood gates at Newark whose only purpose would seem to protect the CRT yard from flooding.

[Mac of Cygnet]

There are of course flood gates (separate from the lock) at Torksey and Selby.  I didn't know about the Selby one until I saw this metal structure being wound across above the lock last year.

[Grebe]

The Chesterfield canal has a flood gate at the start of the remote section at Tapton in Chesterfield.  The original plan was to have an aqueduct across the River Rother to reach a terminal basin on the west side of the river.  In the event the canal was put into the river and the basin opened on to the river.  Still doing its job.

[Pluto]

I would expect it to have something to do with the flow in the river and the likelihood of flooding, though there are probably other reasons. The M&IN did use stop gates on some cuts (see 1st edn OS), and the 1880s river improvement proposed having them on some of the short new lock cuts. They are not seen on the earliest Weaver plans, as the locks were generally associated with a weir, so no length of canal, though neither are they indicated on the 1830s improvement plans, which had longer canal sections.

[magpie patrick]

Thanks for all this - a definitive list may get started, although I may leave flood gates out. My first recollections of flood locks was when we went on a hire boat holiday in 1973 on the Aire and Calder and Calder and Hebble. There was then a hire company at Haskayne and someone had wanted a one-way hire to Leeds, so we picked the boat up (Wirral Dawn I think) and had a week in Yorkshire before doing the L&L back to Haskayne. I'd have been 7 but clearly recall going through locks with deep chambers and massive gates but the gates open at both ends. We also were stuck on the Selby Canal for a day with the Aire in spate and the next day had to work Haddlesely Flood lock going upstream - a lift of about a foot from memory, having been level on the way down. 

 

[magnetman]

The river Wey navigations have flood locks with two sets of gates and paddles in the gates. 

 

I've only ever been up there in the summer when they are open both ends but they do look like they might work as locks if required. They separate river sections from canal sections. 

 

ETA picture of walsham gates closed during flooding (Google image search) 

 

There are paddles in the gates but they are not windlass operated so not quite sure if it is a useable lock when closed but I imagine it was once. 

 

There is also a set of gates above these visible in the photo which would obviously form a pound lock if closed. 

 

And there is a large Weir to the left opposite the moored boats. 

 

Edited May 10, 2020 by magnetman

[Scholar Gypsy]

Tidal gates. Broadly three sorts I think. First a single pair of gates to keep the tidal river out, navigation up to the tidal river not possible

• West Stockwith, tidal Trent
• Torksey. (NB the outer gates don't have paddles on)
• Boston Grand Sluice
   

Then a second pair of gates that face the "wrong way" and enable you to lock up to tidal water

• Keadby Trent
• Bow locks, London (except at very high tides)
   

Radial or guillotine gates that enable up/down operation

• Limehouse
• Three Mills Lock
• Denver sluice
• Salters Lode (a guillotine and two pairs of V-doors)

I noticed some flood gates on the Erewash, about half a mile above Trent Lock, that stop the Trent flooding Long Eaton

[magpie patrick]

On 08/05/2020 at 07:42, pearley said:

Richard T has forgotten the flood gates at Newark whose only purpose would seem to protect the CRT yard from flooding.

This in a way starts to answer my question 

 

Flood gates/Flood locks are situated where there is something to protect! Looking at the ones on the Boyne they are all on longer cuts that get some way above the river in that length, and one cut has breached since the navigation closed presumably as a result of flood water overtopping the banks of the lock cut. 

 

The ones without guard locks are short and the lock is more or less next to the weir so overtopping is not such a problem 

[Pluto]

This 1715 view of Leeds Lock shows a typical early navigation lock, where the lock cut just allowed boats to pass a weir.

[Grebe]

Should the Mutford Lock at Oulton Broad be considered?

 

Between Oulton Broad and Lake Lothing it is tidal at either side.  As well as allowing navigation it also prevents the North Sea, via Lake Lothing flooding into Oulton Broads and the Southern Rivers.  water is tidal at both sides, but HW at the Inland side is about 5 hours before HW at the Seaward side.

[ditchcrawler]

3 hours ago, Grebe said:

Should the Mutford Lock at Oulton Broad be considered?

 

Between Oulton Broad and Lake Lothing it is tidal at either side.  As well as allowing navigation it also prevents the North Sea, via Lake Lothing flooding into Oulton Broads and the Southern Rivers.  water is tidal at both sides, but HW at the Inland side is about 5 hours before HW at the Seaward side.

I wouldn't call it a flood lock, Its not left open for any time at all, the gates at one end are always shut.

[Heartland]

The issue of whether to add a flood lock, or not, is a question that has several possible reasons. Yet a factor may be through developing experience of how to deal with boats navigating a river where a flood might endanger navigation,

 

The original navigation as pointed, out by Pluto, may well be a simple lock, as was the case with the Aire & Calder at Leeds and other navigations in the country. As traffic increased a limited and short lock cut had a disadvantage to those craft where there was no space and then there was the danger of being swept over a weir as the current speed increased.

 

With tidal waters, there are other factors as the flow of water changes from one direction to another. These considerations must have been a factor in the making of the Half Tide Lock.

 

 

Tomorrow is that lamp on the marsh, which a traveller never reacheth

Martin Tupper  

[Pluto]

On a number of river navigations, the Barrow in Ireland being a good example, boats have to pass alongside the weir to access the lock when travelling downstream. Was this because having the lock so close to the weir reduced the possibility of siltation in the lock cut? Whatever the problem they were trying to overcome, river navigations built later tended to have the lock at the lower end of the lock cut. A flood gate or lock at the upper end would have kept siltation and rubbish in the canal down to a minimum during floods. There does seem to have been a change in design in the mid-18th century, with locks being built at the lower end of lock cuts. Come on Patrick, you are going to have to write about the change in design for lock cuts on navigations, and publish!

[Chris Lowe]

Flood gates for the Louth Navigation at Tetney.

 

 

Flood gates for Bourne Eau at Tongue End

 

[magpie patrick]

Okay - I'm talking about locks at the upper end of a section of canal where it joins or rejoins a river that are normally level except if the river is high - I am therefore NOT talking about locks onto a tideway, locks that can operate both ways or locks that normally have a change in level - these are different albeit sometimes subtly so. 

 

At the moment I'm excluding flood gates too, but only because it isn't always as easy to be sure where they are - flood locks are usually listed in mileage tables such as Bradshaws, flood gates get missed

 

The distinction of a flood lock is that, at face value and at summer levels they are not needed - in effect the navigation could manage without them were it not for the risk posed by flooding, whereas locks like Rotherham lock which always has a small lift are not flood locks, at least not for the purposes of this discussion. 

 

Longer lock cuts, which are more likely to need flood locks, were often a result of either improved navigation (Broad Cut on the C&H is over 5 miles long and has seven locks on it excluding Thorhill Flood lock at the top end, and replaced previous, shorter cuts) or avoiding shallows (Oldbridge and Rosnaree Cuts on the Boyne) - in both cases navigation was better served by a longer cut. Cruicetown cut on the Boyne shows one of the problems, in that with the guard lock no longer guarding, the lock cut has burst its banks and the river now runs that way. 

 

 

4 minutes ago, buccaneer66 said:

Flood gates for the Louth Navigation at Tetney.

 

 

 

Now I'm puzzled - what is the lock highlighted towards the top of that plan? The lock next to the Crown and Anchor is clearly the Sea Lock for the Louth Canal

[magpie patrick]

6 minutes ago, Pluto said:

 Come on Patrick, you are going to have to write about the change in design for lock cuts on navigations, and publish!

 

I am, aren't I...

 

Have you notices in your picture there are people walking along the crest of the weir? 

The Barrow Locks are an interesting comparison with the Boyne as the Boyne lock cuts have a habit of disgorging boats almost next to and above the weir crest, which must have been hair rasing in strong stream conditions, coming downstream with a boat on the end of a towrope and the flood lock gates closed...

[Chris Lowe]

That isn't a lock at I highlighted Tetney it's just a set of flood gates, it's named wrong on the map.

[Pluto]

20 hours ago, magpie patrick said:

Have you notices in your picture there are people walking along the crest of the weir? 
 

I don't think there is a bridge across the river here, so it is probably the easiest way to cross on foot.

[David Mack]

 

57 minutes ago, Pluto said:

I don't think there is a bridge across the river here, so it is probably the easiest way to cross on foot.

A bit perilous though!

Edited May 17, 2020 by David Mack

[Heartland]

A factor when looking at maps is that a flood gate does not always signify a navigation, far from it flood gates are simply that a gate for the protection, in some form of the flow and intended to reducing the impact of flooding. With mill streams, flood gates were part of the water management system. In Birmingham we have a Floodgate Street, which is so named because a flood gate and channel connected with a mill on the River Rea.