Medano Creek, Great Sand Dunes NM, Colorado

I liked the contrast in this scene. Those "mountains" in the background are in fact the dunes.


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Medano Creek is one of those little natural wonders...

It begins as snowmelt in the Sangre Di Cristo mountains, above Great Sand Dunes National Monument. It then runs down the mountainside and finally runs alongside the dunes. It plays a few important roles, as the creek, almost alone, helps keep the dunes' border in check along their Eastern side. It also provides a lush riparian (streamside) environment that would not otherwise be there, and which helps to keep a lush variety of plant and animal life flourishing within the park's boundaries. The creek is ephemeral however, and so after the late summer and early fall months, animals must rely on rainwater and other sources of water to drink. While the creek is flowing, however, it is common to find Coyote and other animal tracks leading down to the creek in the early morning hours.

Medano creek never reaches more than about a foot deep, and is mainly just a track of water sliding over the sand, looking almost like low tide at a beach. It is partially because of this that it displays a particular phenomenon (phenomena?) known as "surge flow." The sand that the creek flows over builds hundreds of tiny ridges called anti-dunes, as the creek carries grains of sand. These anti dunes act as mini dams, holding up a small amount of water. The water builds behind these ridges and finally breaks free, creating a chain reaction that breaks many of the anti-dunes along the way, forming a miniscule "flash flood" of sorts. These "surge flows" look to be tiny ridges of water flowing down the creek, with more water behind them of course, and are very interesting. In the summer, when flow is high in the creek, these surges can be up to 3 inches in height. This phenomenon is seen, to my knowledge, no where else in the world, although I am sure that I am wrong about that.