Canyons are formed by rivers, but the colorful scene before you wasn't created by one. Bryce "Canyon" is, instead, a series of bowl-shaped drainages called "amphitheaters" that only contain water when rain or snow fall into them. As this water drains east joining the Paria River, the plateau rim erodes away with it. This process causes the park's many amphitheaters to enlarge at a rate of one to four feet every century.