Case Study: Promoting the Stability of the óbidos Lagoon Inlet

The stabilization of tidal inlets by jetties interrupts the littoral drift and has negative visual impacts. This paper proposes an innovative solution to improve the stability of a tidal inlet (the óbidos Lagoon, Portugal) and minimize maintenance dredging, while avoiding the disadvantages of the traditional solution. The new solution has two key features. First, transverse channels are dredged over the tidal flats to promote ebb dominance, thereby improving the ability of the lagoon to flush out incoming sediments. Second, a partially submerged guiding wall near the southern shoreline, together with the existing guiding wall in the northern shore, prevents the movement of the inlet channel and concentrates the ebb flow in the channel. Analyses with empirical, numerical, and analytical models indicate that the solution improves the stability of the tidal inlet and reduces the accretion in the system.