Tidal observations at Ria Formosa, Algarve, Portugal

Abstract

The apparent persistence and stability of multiple tidal inlets in coastal lagoons are important for a variety of reasons, such as water quality, navigability and beach/barrier stability. To identify and study the processes controlling the persistence of multiple tidal inlets, the hydrodynamics of the system have to be better understood. This project is part of a larger study (INDIA) examining general tidal inlet processes. The present components consist of a numerical simulation study of processes controlling multiple inlet stability, combined with exhaustive field measurements. This report addresses only the second component. The analysis uses as study site and main source of data the Ria Formosa lagoon in Portugal, which has multiple and historically persistent inlets. For the numerical simulation model, field measurements are needed to provide (i) updated bathymetry of the inlets, in situ measurements of (ii) water level fluctuations within the estuary and (iii) flow velocities through the inlets. This report gives first a brief description of the instrumentation used in the field (section 2), then describes the methods used to deploy the instruments, perform the surveys and gather the data (section 3), explains the procedures for data reduction and show some results (section 4 and Annex).