How deep do flood waters have to be before freight trains stop using them?

I live in Missouri and, as everybody knows, we have a lot of flooding going on. We also have a lot of freight trains that cross through our state. There's one in particular that runs along the Mississippi River that seems to be flooded over quite often. So I wondered... How deep do flood waters have to be... show more I live in Missouri and, as everybody knows, we have a lot of flooding going on. We also have a lot of freight trains that cross through our state. There's one in particular that runs along the Mississippi River that seems to be flooded over quite often. So I wondered... How deep do flood waters have to be before freight trains stop using them?
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