Antidunes migrating upstream

Medano Creek is a sinking stream, but of a different kind than we’re used to in the karst (eroded, effectively porous/fractured limestone-type) geology we’re used to in the southern Midwest. Here in southern central Colorado, the sandy, wind-deposited soil forces the stream aboveground here and there and lets it disappear to flow slowly through the sand elsewhere.

The snowmelt sediment and specific landform slope combine here to have a strange thing happen over and over in Medano Creek: the little dune-like riffles collapse and the current immediately rebuilds each, but *slightly upstream*. This is mighty unusual/rare. Normally dunes and other fluid-sculpted sediment deposits migrate downstream/downwind (“saltation” from the latin word for jumping), not up, as the flow takes a hold and transports each particle.

So, students, how would you have to manage this area’s onsite use and upper watersheds to protect this rare phenomenon’s existence and value at Great Sand Dunes National Park and Preserve?

Site: Medano Creek at Great Sand Dunes National Park & Preserve