Olivier.G., Senechal.N., In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.), Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1557–1562, ISSN 0749-0208.-->
Swash hydrodynamics were investigated on an intermediate beach under calm, constant offshore conditions using runup data from video measurements at the scale of a single high tidal cycle. Two different local profile changes occurred on the upper face of the beach between two consecutive days (20cm of erosion and 21cm of accretion). Two cross-shore transects have been chosen for each of the two maximum profile changes (two Accretive Transects and two Erosive Transects). The swash zone was associated with moderately reflective conditions (Iribarren parameters up to 0.9 and a beach slope of 0.058–0.072). Results show a strong disparity in the mean runup heights between transects of the two areas; mean runup elevation for Accretive Transects being twice higher than for Eroding Transects while energy partitioning between incident and infragravity energy was very similar and consistent with moderately reflective conditions. At the scale of the single swash event, results show that uprush typically exceeded backwash duration by ~ 0.8s for Accretive transects. Nevertheless, the general observed trend is a quasi-symmetrical uprush and backwash durations and velocities, consistent with previous observations. Regarding the upper beach slopes, the Accretive part became slightly flatter while the Erosive one became steeper but both tending towards the same beach slope, suggesting that the upper beach seems to adjust towards an equilibrium profile through a balancing of the upper beach face.