The waves along the main diagonal of this image are a set of antidunes. Antidunes form when streams flow really fast (see the diagram below from Mike Leeder's book Sedimentology and Sedimentary Basins). The dunes migrate upstream rather than downstream like regular ripples. I sat and watched these move upstream about 10 cm (1/2 wavelength) in less than 30 seconds. These dunes were in the stream that flows into the ocean at McClure's Beach, within Point Reyes National Seashore.