Soils and Geomorphological development of the Haff Delta of the Vouga River (Portugal)

Abstract

The Vouga basin is situated in the Western part of Portogal, in the Iberian Peninsula. Owing to the Mediterranean influence, both the rainfall and the river flow are very irregular. For the most part of its course, the Vouga flows through the Old Iberian Meseta. Near the sea, it crosses a lagoon containing modern alluvium. The lagoon is enclosed by sand dunes-partly levelled by human action or otherwise-and its greatest extent is along the coast, forming a haff delta. Most of the soils of the area are Humic Cambisols; in the western part, Regosols, Podsols, Fluvisols and Gleysols can also be found, as well as Gleyic Salic Fluvisols. In the beginning of the Holocene (or Flandrian) the coastline was situated much more to the inland. Afterwards the Vouga outlet began to form a delta and some small transgressions and regressions seem to have taken place. The development of the zone must have been influenced by the coastal lagoon, with its microtidal characteristics. The hydrological variation of the Vouga River and its tributaries seems to have been very important to the distribution of the sediments. The type of sediments appears to be closely related to the rocks that occur on the river-basin.