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ABSTRACT
Pires, A. R., Freitas, M. C., Andrade, C., Taborda, R., Ramos, R., Pacheco, A. Ferreira, Ó., Bezerra, M. and Cruces, A., 2011. Morphodynamics of an ephemeral tidal inlet during a life cycle (Santo André Lagoon, SW Portugal). Journal of Coastal Research, SI 64 (Proceedings of the 11th International Coastal Symposium), 1565 - 1569. Szczecin, Poland, ISSN 0749-0208
The morphodynamic evolution of the barrier/inlet of Santo André and relationships between tidal prism and morphological parameters of the inlet were analyzed through seventeen topo-bathymetric surveys. Following the artificial opening of the inlet (March 9, 2009) a prolonged ebb occurred, currents peaking at 6 m/s and excavating a linear V-shaped channel. Sediment eroded from the barrier formed an ebb delta. Two days later the channel deepened to -1.5 m (MSL), while a flood delta started to develop. Eleven days after breaching the ebb-delta migrated shoreward and partly changed into a swash-bar, inducing southward rotation of the inlet channel, which became larger and flat-floored, its depth remaining invariant (-1 m MSL). In the following week it accreted and extended southward, inducing meandering and extension of the channel that started silting up. Three weeks after breaching, the swash-bar offset the inlet, the channel became sand-choked and swash accretion reshaped the bar into a berm. During the next 5 days the inlet closed and the berm rapidly accreted to an equilibrium height, without significant changes until September. Between November 2009 and January 2010, winter waves promoted a new accretion pulse, the berm crest reaching +3 m MSL in December and +4 m MSL in January. Following previous studies on the stability of tidal inlets, the Santo André tidal prism is higher than expected considering the observed minimum cross sectional area. This probably happens because this inlet is smaller and most of the channel gorge develops above MSL, in contrast with the large systems studied by those authors.
ADDITIONAL INDEX WORDS: inlet evolution, currents , tidal prism, inlet cross section
INTRODUCTION
The Santo André Lagoon is located 80 km south of Lisbon, in the southern half of the Tróia-Sines littoral arc (Figure 1A). The lagoon displays a complex morphology, being constituted by a main central basin with maximum dimensions of 2 and 1.5 km in the N-S and W-E directions,...