Caldera is the first Class IV on the Upper Klamath. It’s a long, continuous rapid with a lot going on, so take the time to scout this from river left. The main objective of this rapid is to avoid the Mushroom Rock, which is a steep pourover about halfway through this rapid. It’s possible to go right or left of this feature. Most of the current is pushing to the left, so some boaters choose the left line and let the river do the work. The right line involves working hard right, but below the Mushroom Rock, you are farther from the left bank. Below the Mushroom Rock, the remainder of Caldera is a mix of waves and rock-dodging. There’s a large eddy on river right below this rapid, great for looking upstream for fellow boaters.
Keep in mind that this is a very shallow rapid, with sharp rocks, so you’ll want to avoid carnage here (as is usual for boating…)