The Plumas National Forest has more than a million acres and straddles the transition zone between the Cascades and the Sierra Nevada. Where the Sierra block disappears under the younger volcanic rock of the Cascades on the forest's northern boundary near Lake Almanor, the transition is not easy to perceive.
The forest incorporates the watershed of the Feather River, which has carved many canyons and ravines full of cascades and whitewater. Portions of the Middle Fork of the river and three of its tributaries have been designated the Feather Falls Scenic Area. The most spectacular of the waterfalls is Feather Falls, just above Lake Oroville, which drops 640 feet.