Why don't canals flood?

Question

Just occurred to me that I've never seen an overflowing canal!

Answer 1

Unlike rivers, water does not flow through canals (a canal is sort of like a very long, skinny swimming pool). Canals are designed strictly to enable boat & barge transportation, so by preventing the water from flowing, you can travel equally easily in both directions.

So, this means canals have no "natural source" of inflow, the way rivers do. When the canals run a little low on water (due for example to evaporation) or a little high (due for example to heavy rains), the canal operators open some valves to let some water in or out.

Even a very heavy rain will only raise a canal's water level by an inch or so (just like your swimming pool). The reason the level in rivers rises by much more, is because the rivers are collecting all the rain runnof from the surrounding land. This isn't the case with canals.

Answer 2

Well, rivers flood because they are the natural drainage channel for rainfall.
When it rains heavily, the rainwater makes it's way to the river and if there is too much, it causes a flood.

A canal is man made, and is not a natural drainage channel, so rainwater does not make it's way to the canal - so no flood!

Answer 3

Yes they do, i used to live on The Fossdyke canal in Lincolnshire and flooded one winter had to have a gang plank to get on and of my boat. All UK canals will flood they are only 4ft deep lined with clay....

Answer 4

Because they are dredged and the spoil is dumped on the banks they used to do that to rivers and streams till Maggy sold of the Water companies.Now its all profit.And share holders

Answer 5

normally they have locks with sleus gates,