Medano Creek at the Great Sand Dunes National Park is peaking this weekend.

It's flowing in braided channels - each about 10 to 40 feet wide and 1 to 20 inches deep, according to the National Park Service website.

Medano Creek is one of the few places in the world to experience "surge flow" - a stream, flowing in rhythmic waves on the sand.

Three elements are needed to produce the phenomenon: a relatively steep gradient to give the stream some speed, a smooth creek bed with little resistance, and enough water to create surges.

In spring and early summer these three things combine to make waves at Great Sand Dunes.