Repairing it seems easier than if it is underground, but certainly it has a failure mode (leak/ flood) that a normal underground pipe doesn't have. However we'

Repairing it seems easier than if it is underground, but certainly it has a failure mode (leak/ flood) that a normal underground pipe doesn't have. However we're talking about fairly shallow canals (a few metres). I wonder what is the failure rate for reasonably priced semi-flexible prefabricated pipes with a diameter of maybe a metre, or even less.