Defending - Rivers and Forts?

[fluidwill]

Recently finished Balkans '41 and just started France '14 and have a couple of questions with respect to fortified zones placed ON river lines;

1) Do you suffer any penalty for being dug in on the river line or do you just lose the attacker penalty that could be gained if you were behind the river?

2) if you blow a bridge in/under the fort do your defenders suffer supply wise?

I know I can/could find the answers in the manual / on the net but I thought if we discussed it here we all might learn something.