Alternation of beach erosion/accretion cycles related to wave action off Rosarito, Baja California, Mexico

Abstract

A total of 1860 beach profiles were surveyed monthly from October 1995 to December 2003 at 29 control points along the coast of Rosarito (Baja California, Mexico). Sand volumes were estimated for the subaerial beach and related to deep-water wave records off California and nearshore waters at two localities off Rosarito. The spectral analysis of the sand volume time series revealed two main spectral peaks of 12- and 36-month periods. The latter cycle was identified for the first time along Rosarito beaches, showing a slightly larger amplitude on the beaches near the Federal Electricity Commission´ s breakwater and in the southern part of the study area. The contribution to sand movement produced by the annual cycle was 80 m3 m–1, while the transport induced by the 36-month cycle was 50 m3 m–1. The erosion and accretion cycle corresponded to winter and summer, respectively, but this pattern was inverted at two localities. The annual or seasonal cycle of sand volume change, defined in terms of the Dean number (Ω = Hs/wsT), is controlled by the seasonal wave pattern, while the inverted cycle is due to local changes in beach morphology and approach angle of breaking waves. The factor that accounted for this cycle is associated with interannual wave pattern variations and this, in turn, with ENSO events.

Seasonal morphodynamic classification of beaches in Necochea municipality, Buenos Aires Province, Argentina

“…Regarding the seasonal evolution of the morphodynamic states, in winter all the beaches became more dissipative, whereas in summer and autumn they were more more reflective (except Médano Blanco, which was reflective in spring). These results coincide with the morphodynamic behavior described by Masselink and Hughes (2003) and documented for Mexican beaches (Lizárraga-Arciniega et al 2007). An increase in wave height during winter (1.26 m) favors offshore sediment transport and the beach switches to a dissipative state.…”

“…En cuanto a la evolución del estado morfodinámico de las playas a lo largo del año, en invierno todas las playas se aproximaron a un estado más disipativo, mientras que en verano y otoño presentaron un estado más reflectivo (excepto Médano Blanco, donde el estado más reflectivo se observó en primavera). Estos resultados se ajustan al comportamiento morfodinámico descrito por Masselink y Hughes (2003) y observado en playas mexicanas (Lizárraga-Arciniega et al 2007). El incremento en la altura de ola en invierno (1.26 m) favorece un transporte de sedimentos mar adentro, produciendo que la playa se vuelva hacia el estado disipativo; por el contrario, un descenso en la altura del oleaje en verano (0.96 m) ocasiona un predominio de transporte de sedimentos hacia la playa, generando un estado más reflectivo (Masselink y Hughes 2003).…”

Short and medium-term coastal evolution of Necochea Municipality, Buenos Aires province, Argentina

“…This variability could be related to the nearby coastal defenses, as observed by Anfuso et al (2006) in the coast of Morocco. Liza ´rraga Arciniega et al (2007) estimated that in Mexico the coastal structures and the rocky outcrops modified the wave incidence altering the littoral sediment transport and producing erosion and accretion zones. In the study area, A beach, situated toward the west of the port, did not present volumetric changes.…”