Separation of structure and ripples on sand mounds using Hermite functions

<jats:p> A simple method is proposed for the separation of a large-scale structure from small-scale ripples during the evolution of an isolated sand hill or spoil heap eroded by an oscillatory or steady flow by bed-load transport. This method is based on Hermite functions, a mother Gaussian hill and derivatives modified to be orthogonal. It is straightforward to apply and could be used to characterise the geometric properties of any isolated localised hill-like feature such as pollution concentration levels away from an outfall. </jats:p>