Present Hydrodynamics of Ancão Inlet, 10 Years after its Relocation

Ancão Inlet (Southern Portugal) was relocated in 1997 and almost 10 years after its opening has the morphodynamic characteristics and migration pattern predicted by several authors. Its eastwards migration is mostly caused by high W-SW storm events, where the downdrift migration of the channel is accompanied by updrift spit growth and both deltas migrate asymmetrically. The inlet migration rates were computed between three new surveys and several inlet parameters measured, revealing the highest migration rates since inlet opening, an a relative stable inlet cross-section area, width and maximum depth at inlet throat through time. Inlet migration rate was compared with storm events and results showed a relation of this rate with the diminishing of E-SE storm events and an increase of magnitude of W-SW storms. Also, during an unusually powerful ex-tropical storm which affected the study area, an ephemeral inlet breached updrift from Ancão Inlet. The new inlet was competing for dominance of the tidal prism with Ancão Inlet, however it closed after three weeks, showing the hydraulic efficiency of Ancão Inlet nine years after its relocation.