Swen,
There is a cast that I use alot when straight casts can't be done. Think its called the change of direction cast. I false cast parallel to the bank, Then when I want to put it on the water I flick my rod tip so the loop kind of goes flat and goes at a curve out to about a 90 degree angle to the bank. This may help with the slope and obstical problem. Try to stay in a crouch allong the bank to avoid being see by the fish. The description isn't perfect but maby someone can clean it up.

Steven