Ha, Stupid idiots (in the picture, I mean). Assuming that was taken in the wintertime, they have failed to take a water temperature check....
THE FISH ARE BEHIND YOU.
Think they heard me? Actually, they're probably under the one guy, but that spot is already ruined for the day.
Trowpa, its very likely whoever was there before us that day did something like the guy in the green jacket.
Anyway, lack of holding water, yep. There's only about a half dozen decent spots. At least a few of them aren't visible from the road, being even a couple of hundred yards from the access points seems to turn away 90% of the guys. The pictured hole is, quite obviously, the most popular pool on the stream. It's a combination of heavy stocking right there, and the influence of Cacoosing which gives the fish a thermal escape.
gemiller, The triangle things are put in by TU to narrow the channel, and thus trying to cool the water downstream as well as create, perhaps, fish holding structure and some semblence of "current".