Simulated test and depth averaged flow Um due to short and long waves (solid line) and long waves only (dashed line) as function of the cross-shore position. The dotted line corresponds to the wave averaged sediment advection velocity $u_A$ due to nonlinear short waves. Markers correspond to measured undertow flow velocities due to short and long waves (downward triangles) and the sediment advection velocity due to nonlinear waves (upward triangles).