considered as a periodic formation-advection process. A model for estimating the generation frequency of the surface roller is proposed and it is examined experimentally by analyzing the water surface fluctuation downstream of three weak hydraulic jumps based on the fact that the released large eddies may interact with the free surface downstream hence leaving their characteristic signatures. Power spectrum of the surface measurements in each case clearly shows that a band of approximately normal distributed energy centering at a particular frequency exists. The identified center frequencies are found to match the surface-roller formation-release frequencies estimated by the proposed model well.