I'd rather fish down below the dams too. Most of the time. But there are two narrow windows of interest at Canyon Ferry: Early Spring and late Fall. Most of the time the big lake rainbows are too far out and too deep to catch from the bank. Particularly so with a fly rod. In April and November they come in close to the edges, for some reason.
Also.....a few guys I know have been catching walleyes on streamers--in the river between York's Islands and Townsend (above the lake). Two of them (two seasons back) caught a 14lb walleye right above town, less than a mile from the takeout. They got together with their wives and barbecued it the next night. A day after that they found out a 14lb walleye would have been a world fly rod record for 8lb test.