Morphological Evolution of the Obidos Lagoon

Abstract

The Obidos Lagoon, oriented northwest-southeast, developed perpendicular to the shoreline and communicates with the ocean through a narrow and shallow channel that needs constant dredging. This lagoon system was until the 18th century represented on the charts as an estuary which allowed navigation. Historic references indicate that the baymouth bar was formed during the medieval period, creating problems of inlet siltation. The use of cartography and air photographs of several dates establishes a rhythm of verified siltation in the last century, which reflects a loss of lagoon surface area of about 9,600 m²/year.