Beach-line changes at the mouth of Punta Banda Estuary, Baja California, during 1972–2003

Abstract

The spatial and temporal variability of the beach-line position at the tidal inlet of Punta Banda coastal lagoon in Baja California, Mexico, is described from the analysis of ten aerial photographs and two satellite images spanning from 1972 to 2003. The results showed that the maximum tidal inlet width (995 m) occurred in 1980. Changes observed from 1980 to 1985 suggest that the extraordinary sediment fluxes that occurred during the winter storms of 1977/78, 1980/81 and 1982/83 were the main source of sediment inducing the growth of the sediment structures that delimit the tidal inlet. By the end of 1985 a new sand bar appeared on the northern side of the tidal inlet and its formation is attributed to a reduction in the ebb and flood tidal intensity as a consequence of the combined effect of the increase in width of the tidal inlet in 1980, of the extraordinary supply of sediments and of the dominant northeast to southwest longshore sand transport. The net growth of the sand bar that shapes the southern side of the tidal inlet was 53 ha from 1978 to 2003, of which 26 ha are located in the inner part of the tidal inlet. This growth and consequent reduction of the tidal inlet could be the result of a reduction in the tidal prism produced by the great amount of sediments supplied to the coastal lagoon by storms and also by the reduction of the lagoon´s flushing capacity.