When the water is high and fairy swift and clarity not the greatest (ie Squamish) you want to get down to the fish. I fish a 12' 7.5 inch per second polyleader and short 8lb leader to get it down to where the fish are, cast 45 degrees down stream and throw an upstream mend to straighten out the fly line above the fly, this allows it to sink. When the line comes under tension follow the line with the rod tip as it swings across the river, you can thrown in the odd strip if you like. When the line is directly below you strip it back in and start again, often they will grab it as you are stripping it back in. If you are snagging them cast on a sharper angle down stream or change to a lighter tip, unweighted fly etc. You will undoubtedly floss a few with this method, but the amount of legit biters is way higher, especially if you keep the fly travelling just above their heads. I have had most success this year swing a size 6 - 8 pink bead head woolly bugger with a bit of flash to it.
The second method I have had a lot of success with this year is dead drifting. I have been using a floating line with 5' of 8lb leader, a strike indicator on the leader and a weighted pink woolly bugger or similar. Cast or simply flick the line upstream and then high stick as it drifts back downstream toward you, retrieving line off the water to keep it drifting naturally, as it begins to pass you mend so that the line is upstream of the indicator and then start throwing stack mends or feeding line into the drift so the indicator keeps tracking down stream at the same rate as the current, exactly the same as float fishing, if the indicator dips set the hook! If you are snagging fish or the bottom move the indicator down accordingly so the fly is drifting about a foot of the bottom.
Hope this helps.