To the person crossing the river? No. To the reader who may care that it is the longest river in the country (because some people do care to learn about such things)? Yes.

This is a similar strategy to what France did after the Haitian revolution. They showed up with gun boats and threatened to level everything from afar unless Haiti agreed to pay ‘reparations’.

It typically is.

EDIT: I do need to clarify that you can spell it both ways.

Yes, this is correct.