do canals flood?
 

or does the water level get controled by the lock systems?

The one outside my house has never flooded. It feeds into a stream that floods instead :)

Aren't Canal's (usually) a sealed system with very little water input?

In theory, if excess water flowed into teh upper locks, the locks would overflow into the next lower level, and inturn the level below that. Until it meets the river it links up with, or an interim basin that has an overflow weir that dicharges into a nearby stream (Clever folks Victorians, eh? ;) ). Now if the river was already overflowing, then the lower level locks could flood, depending on how high the river is and the level of the lowest lock.

Depends on the design and also whether it is a 'canalised river'. The River Lee has a number of locks on it and has been effectively converted into a canal. However, they have had to install a parallel system of flood control measures along it to.

Each lock has in effect been turned into an island with an automatic barrier put in adjacent to the lock - bit like a very scaled down version of the Thames Barrier. The level can be set remotely to allow for flood waters. In this way the lock levels are maintained and the additional water flows down the river as per normal. That said, with excessive rain, areas can still flood (it did about 3 years ago), but nowhere near as bad as it would be without the flood control system.

Most canals have overflow "sluices" that runn off into small rivers/streams etc.

Sluice.

I love that word lol :)

Most canal levels actually have "overflow" channels that feed water around the bottom-end lock when that level gets too high, rather than allowing it to pour over the gates. Same result though.


M

http://www.deuchars.org.uk/floods2k/erwshnth.jpg

thats the canal where i used to work in 2000, although thats the section after the first lock from the river the flood gates were further up, it can still flood. water tends to be at a higher level during floods ;)

more at http://www.deuchars.org.uk/floods2k/erwshnth.jpg

Canals can often flood, and has been seen very recently with the poor weather. Generally they are protected from the flooding rivers via flood gates which are kept locked when there is a danger. These flood gates can often overflow and sometimes even be opened on purpose to release the pressure on the river. This happened in Doncaster last week when the council asked the waterways authority to open the flood gates in a flood situation to prevent the river from flooding the town centre.

Well I saw water b0ll0cking over the top of some lock gates the other day, a day or so after the bad storms.......it looked like a mini dam!

yes the canal at doncaster has flooded, but as stated this is due to the don river bursting its banks next to it.

Canals systems with locks in them have a 'header tank' reservoir at their highest point. This is to replenish the water that is lost downstream every time a lock is operated. If there is a series of locks in close proximity, there will usually be a smaller reservoir nearby too.
To maintain a constant level, there are generally weirs located at regular points along a canal allow excess water to drain away to a nearby waterway. These weirs are adjustable to allow the water level to be lowered or raised within a limited range, in times of either shortage or excess respectively.

Obviously if the waterway into which they would normally drain becomes flooded, the weir ceases to function

I love Deuchars :notworthy