Assessment of a Sand Spit Morphodynamics Under Extreme Flood Events

Abstract

Spits are landforms that present a complex morphology, which depends on currents, waves, sediment transport, tidal range and anthropic-induced changes. Their position and shape is subject to extreme events like flood river discharges and storms. They can also respond to processes that take place at larger time scales, as plate tectonics, sea level rise or even climatological patterns with teleconnections all over the world, as the well know North Atlantic Oscillation (NAO) or El Niño-Southern Oscillation (ENSO). This is the case of the Douro river mouth sand spit located on the northern coast of Portugal. This naturally dynamic sand spit, which has moved landwards over the past decades, has caused frequent nuisance to navigation, affecting width and depth of the navigation channel. Therefore, a breakwater was constructed in an attempt to stabilise the sand spit and the estuary inlet.