Barchan Dunes of Imperial Valley, California

Three localities with barchans occur in Imperial Valley, California. One group is present in the intradune hollows at the southern end of the large Algodones dune chain along the southeastern side of the valley. The other two localities are west of Salton Sea and include an isolated dune adjacent to Tule Wash and a related dune cluster about 5 miles east near Salton Sea Base. The relationship is indicated because dunes in these two areas share a common sand source and move in the same direction. The Algodones barchans have developed only in the largest of the intradune hollows in response to post-pluvial climatic changes and currently are found to require about 40 years to move across the intradune hollows. The Tule Wash dune is migrating across extensively gullied topography, and engulfment and destruction by a stream in one of the gullies seem imminent in the next decade. A similar fate probably overtook two companion dunes present in 1904. The Salton dunes appear more permanent, although individual members of the group may be destroyed by migration into the Salton Sea. Rate of advance of the Tule Wash dune correlates well with volume changes only when compared on an annual basis; shorter-period changes seem governed more by seasonal wind variation and by topographic effects. In general, rate of dune advance decreases with an increase in volume. The Tule Wash dune has remained asymmetrical for the 9 years it has been observed, and the persistent elongation of the south horn is due chiefly to the wind regime. The consistent slimness of the dune is not completely understood but may be due in part to topography as well as to the strength and width of the oncoming sand stream.