| Abstract: | The seaward mean returnflow or undertow in the surf zone, which compensates for the shoreward mass flux above the wave trough level, is found to be driven by the force imbalance between the wave momentum flux on the one hand and the set-up on the other hand, in qualitative agreement with the model of Dyhr-Nielsen and Sørensen (1970). A model, which quantifies this imbalance, is shown to yield theoretical results in good accordance with experiments when the proper boundary conditions are accounted for. |
