What process caused the accumulation of sand that produced the sand dunes?

The Kelso Dunes depend upon times when the sand grain (sediment) supply is enhanced. This happens whenever the climate is dry enough to expose the raw material of dunes, sand, to the wind. In fact, most of the eastern part of the Kelso Dunes formed when water-filled Soda Lake and Silver Lake dried up, exposing the lake bottom sediment.