At the base of the dunes, next to the visitors’ center, is shallow and wide Medano Creek (medano is Spanish for “sand dune”). Kids love to wade and splash around in its clean waters, building sand castles, trying to dam the water, skimboarding, and basically having a beach-like blast. The creek is seldom deeper than about four inches (but can get up to 11 inches in spots), and it generally starts to flow in late March or April, with peak flow in late May and early June.

Typically, it runs dry in July — although in years with a heavy snowfall, it goes all summer long. It flows in several braided channels, each from three to 20 feet wide. (The entire creek is between 30 and 50 feet across.) Creek flow is always highest in early morning, and lowest in late afternoon.

If your kids think they see waves in the creek, they̢۪re witnessing a phenomenon called surge flow. Sand piles up (forming underwater mini dunes) and then breaks down from the force of the current, which then causes a surge of water similar to what happens when a dam breaks, but on a smaller scale. The effect creates ripples or waves coming at intervals of anywhere from a few seconds to a minute or more apart. In years when the water is high, the surges can be as much as a foot tall!