Flash Locks - how did they work in practice?

[magpie patrick]

One thing I've learned on navigation history is never say never - things that are less likely probably happened less often but almost everything was probably tried somewhere. 

 

My thoughts on the boats carrying a portadam with them are that it wouldn't work very well. Leaving aside the expense and bulk, think it through. The portadam works on the fenland staunch model in that the river is free flowing until an ascending vessel needs extra depth, at which point a dam is contructed behind the vessel. Get the kit off the boat, build the dam, let the level rise and carry on

 

Until the next shallows, at which point the necessary kit is all at the last shallows, walk back and get it? The canvas will be pretty bulky! Carry two kits? Well yes but everything being carried is coming out of cargo space, and how many kits would you carry? The Brandon River had 8 staunches in 1904.

Now reverse it going downstream, walk ahead with all that kit?  

 

I would have thought it more likely that material for the dam was collected local to the site, and left there when the damn was dismantled, possibly with the boat carrying a couple of stout fence-post type timbers as it might not have been so easy to find these to hand. I will have to read up again but I think this is how stone for Glastonbury Abbey was rafted down the Sheppy from the quarries at Doulting. That's another instance of one way traffic - the stone was probably carried on rafts that were broken up and used in the construction of the abbey. 

[Ray T]

 

 

@Tam & Di

Edited July 26, 2022 by Ray T

[Pluto]

I do think that young Magpie has a point regarding materials for a staunch being kept on site, and not moved up- or downstream. Having handled hold sheets and sails on traditional boats, they are not light, particularly when damp, and it would not be good for them to be left damp for any length of time. Another factor to consider is where the local skills came from, with waterways in eastern England being very much influenced by engineers from the Low Countries, whilst on the Thames and Severn there were probably other more local influences. What was a spade somewhere would be a shovel somewhere else, so interpreting any written descriptions can be difficult. This is made worse by people who could write not really being technically-minded, and I have found some very strange 17th and 18th century descriptions.

 

Technical development also affected the design of flash locks, and I have just translated a description of the Charente around 1780 where three mill weirs had been combined into one fall. Water wheel design was improving at this time, so three undershot wheels, which would each only require a 10 inch fall, would be replaced by a single high breast wheel, which would need at least 30 inches of fall.

 

Time pressures would have been less, and on the Stecknitz Navigation a small fleet of boats would pass once a week. In the correct circumstances, it would be almost as easy to pass ten boats as one boat. This was certainly the case on the Grand Canal in China which used flash locks almost exclusively, though inclines were used on the extreme southern end, and there were a couple of cases where the flash locks were brought close together to form a sort of Chamber lock. They didn't catch on.

 

Below is the navigation weir in the middle of Prague, which had a sort of gap in the middle through which timber could be rafted or boats pass. The stone walls at either side were long enough to ensure that the slope of the water was not too great, and this was one of the changes which occurred when navigable weirs were raised in the late 18th and early 19th centuries.

[Jeremy Lander]

All good stuff thanks! I know what Magpie Patrick means, as an architect I always want to know exactly how things work in practice and often a text description can be rather tantalizing. "They would build a temporary dam of turfs logs and mud" sounds plausible but how did that work exactly? And "on either side" doesn't quite make sense either. I wonder what the primary source is for this. I also take the point about hauling wet canvas and the enormous bother of getting the tackle out once it had served its purpose. But my feeling is that, given the resourcefulness and ingenuity of people, the next to non-existent road network and the enormous financial incentive of, say, a Norman lord ordering 2k tonnes of stone for the construction of his castle, or even a miller ordering a French mill stone, was huge. They WOULD have found a way. And I think there was probably a combination of flash locks, temporary staunches, semi-permanent staunches at known tricky spots etc etc. As for transporting their kit there were horses and small boys who went up and down the river banks jumping the various obstacles along the way, as painted by John Constable on the Stour. And they had time, lots and lots of time.

[Tony Brooks]

It looks to me as if that horse is towing the barge.

[Pluto]

As someone who used to dress millstones as part of my job, I would say that they are pretty easy to move singly or in pairs on a shallow draft boat, though much more difficult by land. Providing large quantities would be more difficult, but by no means impossible. As ypu say, time was of less importance two hundred or more years ago. On the supply of stone for building projects, by the mid-19th century things were highly organised. Jesse Hartley, when building Liverpool Docks, had colour-coded drawings showing when individual stone items were expected to be delivered from Liverpool Corporation's quarry in Scotland.

Horse towage of boats was a comparatively recent thing, and was probably first used on the Trekvaart in the Netherlands. These were passenger boats, not for carrying heavy loads, and contemporary European literature does suggest that horses were first used extensively for towage in England. Previously, everything had be hauled by humans as there was no real need for a towpath on a river. On a canal it was much easier to build a towpath using the embankment of earth thrown up when excavating the canal. That said, I have seen illustrations of horse towage on rivers in Germany, though I am not sure about dates. German technical books of the early 19th century certainly considered the reduction in horses needed for water transport compared to road to be a major factor, releasing land used for feeding the large number of horses used on roads and turning over to agricultural production for feeding people.

[magpie patrick]

2 hours ago, Jeremy Lander said:

All good stuff thanks! I know what Magpie Patrick means, as an architect I always want to know exactly how things work in practice and often a text description can be rather tantalizing. "They would build a temporary dam of turfs logs and mud" sounds plausible but how did that work exactly? And "on either side" doesn't quite make sense either. I wonder what the primary source is for this. I also take the point about hauling wet canvas and the enormous bother of getting the tackle out once it had served its purpose. But my feeling is that, given the resourcefulness and ingenuity of people, the next to non-existent road network and the enormous financial incentive of, say, a Norman lord ordering 2k tonnes of stone for the construction of his castle, or even a miller ordering a French mill stone, was huge. They WOULD have found a way. And I think there was probably a combination of flash locks, temporary staunches, semi-permanent staunches at known tricky spots etc etc. As for transporting their kit there were horses and small boys who went up and down the river banks jumping the various obstacles along the way, as painted by John Constable on the Stour. And they had time, lots and lots of time.

 Let me start this with - I'm not arguing with you, just trying to work with you to piece things together - my usual approach is to look at multiple sources

 

The picture is a Constable painting of the Stour, which had athletic tow-horses. These beasts had to get on and off the barge as well as leap over fences (the land owners wouldn't allow gates, only stiles) and the Stour had locks. It is the Stour, among others,  that I think of when I think "never say never" because they did some odd things on the Stour!

The origin of what we now regard as two types of flash lock are completely different - the staunch (normally open) is primarily a navigation tool where as the flash lock (normally closed) is a necessary evil for the miller whose main purpose is a head of water for the mill. The portadam is a staunch - a dam for navigation where no dam exists. 

I suspect the method chosen would depend upon available resources - I am sure that somewhere a portable system was used but it would be because other methods were not available or not viable, economics worked then too - often gathering wood, stones and mud from the bank would be practical (beavers manage it - you don't see them carrying sheets of canvas round!) but where it's not then other solutions would be needed (beavers don't build dams where there are no trees!)  

 

There will be a big difference between what happened in the 18th century when it came to staunches and what happened in the 12th century, with not much happening in between. @Pluto makes interesting comments with the shallow draught of the boats how small the head of water needs to be for an undershot wheel, and I guess there'd be no other type in the 12th Century - a one foot lift on a draft of 18 inches can be achieved by putting logs or planks across the river. Navigation could be very seasonal - even in the early 20th Century there are places Bradshaw (1904) describes as "being navigable when there is fresh in the river" and as you comment they had plenty of time, time enough to wait for plenty of fresh. 

 

Traffic was often remarkably light too - I seem to recall noting several years ago that traffic on the branch to Corps Landing, a branch off the Driffield Navigation, amounted to 3 barges a year at it's busiest. Corps Landing is one farm basically. in the 12th century, with the much smaller population and serving only the occasional big load, then one-off damming of the river would make a lot of sense. 

Traffic's like that from Doulting to Glastonbury intrigue me because they weren't a one off - several thousand tonnes carried a few tonnes at a time - it intrigues me, but I have very few answers! 

[David Mack]

11 hours ago, magpie patrick said:

I seem to recall noting several years ago that traffic on the branch to Corps Landing, a branch off the Driffield Navigation, amounted to 3 barges a year at it's busiest

But that is a natural river course branching off the River Hull. After Struncheon Hill Lock was built it would have had enough depth for navigation without needing any specific navigation works. So it's really an incidental waterway that just happened to be navigable when convenient.

[magpie patrick]

34 minutes ago, David Mack said:

But that is a natural river course branching off the River Hull. After Struncheon Hill Lock was built it would have had enough depth for navigation without needing any specific navigation works. So it's really an incidental waterway that just happened to be navigable when convenient.

 

Indeed, that is it's modern status (modern as in 18th century and later) although the name Corps Landing (or Corpslanding) is of Norse origin and dates back to the Danelaw - the Norse almost certainly reached Corps Landing via the river. 

I think the point I'm making is don't over estimate how little traffic would use some of these waterways and how patient they were. If you add places that were only accessible on spring tides, only accessible with "fresh" in the river, and were accessible easily but not much used the one gets a picture of navigation very different from the modern era.  

[David Mack]

Indeed. And before Struncheon Hill Lock was built I imagine the River Hull and its tributaries up to Frodingham Bridge, Corps Landing and the Driffield Canal were only navigable at high tide.

 

 

Edited July 27, 2022 by David Mack