In the Sierra it tends to be an early-season phenomenon, with snowmelt-swollen streams that subside or even disappear later in season. PCT thruhikers, for example, have to wade a lot of streams, some pretty scary, that we less-ambitious folks can just rock-hop.

Last summer, though, I had to wade the West Walker on the trip out because we had several days of rain that raised it a couple feet. I was quite grumpy about having to stop and switch to my flip-flops and get wet up to my rear, but it actually felt great.