Barchan Dunes of the Salton Sea Region, California

Abstract

Rates and directions of motion have been determined for 19 barchan dunes near the Salton Sea, California, for the period 1941 to 1981. Between 1941 and 1956 these barchans moved with an average speed of 15.5 m y⁻¹ in the direction 89° T (T = from true north). During the period 1956–1963 the rate of motion increased to 24.4 m y⁻¹, and the direction shifted northward to 80° T. Finally, during the 18 years between 1963 and 1981, the rate of advance of these dunes declined to 16.2 m y⁻¹, and the bearing was again more southerly, 96° T. Fluctuations in speed and direction are superimposed on changes in the dunefield brought on by an apparent diminution of sand supply over the last 140 years. A decrease in the sand supply may be because of increasing maturation of an upwind, incised drainage pattern that interferes with sand flow and dune mobility, and to modern channelization associated with highway construction. At the downwind edge of the dune area, some barchans are entering the Salton Sea. They may ultimately become vegetated shoreline dunes. Members of the southernmost group of dunes appear to dissipate entirely before reaching the water. The overall picture is of a dunefield declining in area and population owing to a combination of adverse geological and cultural developments.