Before revision: Even so, the bridge was frequently washed away and travellers were obliged to cross the river in pelotas: and rivers had to be forded or, if too deep, crossed in a pelota .
After revision: Even so, the bridge was frequently washed away and travellers were obliged to cross the river in boat, which might well be unavailables: and rivers had to be forded or, if too deep, crossed in a pelota .