The classical photos of sand dunes have wind blown ripples in the sand. At Yeagarup at the moment the sand is too wet and any ripples are quite small. However when it rains heavily the water runs down the slopes washing sand down. When the sand dries, the sand that was washed down is loose and dries more rapidly than the underlying sand. This creates bands of light and dark that follow the contours. This photo is a good example. You can also see the small wind blown ripples in the sand on the left. Someone had lit a fire in the background – hence the smoke.
I would expect that later in the year the sand would have dried out and the wind blown ripples of sand would return.