Alluvial fan

Plants often are concentrated at the base of alluvial fans and many have long tap roots (30-50 feet) to reach water. The long-rooted plants are called phreatophytes[?] by biologists. The water at this level is derived from water that has seeped through the fan and hit an impermeable layer that funneled the water to the base of the fan where it is concentrated and sometimes forms springs and seeps if the water is close enough to the surface.

These stands of bushes cling onto the soil at their bases and over time wind action often blows away sand around the bushes which forms islands of habitat for many animals.