Mark P. Bradshaw


This paper presents observations of currents recorded in the swash zones of a number of morphologically different types of beaches in order to demonstrate the large variability in run-up patterns that exists primarily because of variability in beach face and surf zone configuration. Run-up spectra are shown for steep and flat beaches under low (<0.5m) and moderate (0.5-2.0m) wave energy. The longshore variability of run-up patterns on rhythmic beaches is also discussed. On reflective beaches run-up occurs only at incident wave frequency under low energy conditions and at both incident frequency and its first subharmonic under moderate energy. Low energy dissipative beaches exhibit a range of frequencies across the swash zone from incident through low frequency infragravity. As wave height increases on flat beaches, high frequency oscillations vanish leaving a concentration of energy at low infragravity frequencies. On more complex inshore rhythmic topographies under low to moderate energy conditions, alternating transverse bars and troughs give rise to a close spatial co-existence of zones of surging, reflective run-up and zones of over-running progressive bores of the type observed on flat profiles.


topographic control; run up; run up variability

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