Re: Salmonfly hatch on the Deschutes...
On large rivers I find a majority of the char and salmon I catch to be close to the bank especially if the water right off of the bank is deep and slower than the current 30 feet out. For rainbow trout I can't offer anything I would cite as a rule. They seem to prefer to be in a good hold right in the flow of things. I expect this changes as waters become more turbid and a meal is easier to find close to shore.
Other than when a fish is just plain hanging / holding, somewhere in a rivers' channel the best way to find one is to think hard on where the groceries will be easiest to find. When they rest or hide, they rest & hide, but when they need to feed they are going to do what instincts tell them to do. Everything that does not want to be swept down stream by increased water velocity will migrate to areas where they can find some level of relief from the current. Of course nymphs, especially big tasty ones like you guys have down there right now are on the rocks on the bottom however they too will try to avoid being swept away either by clinging into crevasses or in the case of the stone & what we call the salmon fly they too will head toward shore so they can crawl out to hatch. If runoff keeps things high I would be developing strategies for working the near shore environs thoroughly.
I don't see much or do much dry fly fishing since moving here to Alaska but prior to the move I had plenty of years to take note of what happens during both flood & drought on many rivers and streams.