Each year Medano Creek at the Great Sand Dunes National Park transforms into a water lover’s paradise due to a rare natural phenomenon. Surge flow in the park occurs when melting snow from the nearby mountains cascade down onto the sand ridges. This makes the sand create underwater ridges, which will produce waves every 20 seconds. This kind of surge flow can only take place in a sandy creek bottom without pebbles or stones, because sand will form antidunes when water cascades over it, creating little ridges that result in waves. This creates ideal conditions for tubing and wakeboarding.
When snowfields in the Sangre de Cristo Mountains begin to melt in the spring a surge of water floods the shallow creek, and the Great Sand Dunes National Park starts to look like it hosts a beach party. People set up tents and have picnics while children enjoy the water and have fun with inflatable tubes. People call Medano Creek "Colorado’s natural beach" with beautiful sand dunes completing the picture.
The flow in Medano Creek occurs between April and June, peaking from late May to early June. It usually dries up by the end of July.