Modificações na geomorfologia marinha a partir de estruturas portuárias: o caso do Mucuripe, Fortaleza – Ceará

Abstract

The Fortaleza coast has undergone important changes in the coastline, since the 19th century, mainly due to the mitigation structures. The aim was to analyze the bathymetric evolution of the North coast of Fortaleza from the implantation in 1945 of the Mucuripe harbour. The study area is delimited by the Titanzinho groin and the wastewater outfall. Digital bathymetric models were carried out from the nautical charts of the Diretoria de Hidrografia e Navegação - DHN between 1945 and 2014. The presence of two sectors was evidenced: 1 – adjacent to the Mucuripe headland, with the substrate directly modified by port management activities; 2 - the rest of the submerged area to the outfall. The first sector is marked by the creation of eminently depositional areas due to the Titã jetty (shadow hydrodynamic effect), Titanzinho groin (obstruction of longshore current) and the Pier (Titã's hydrodynamic shadow effect and the advance of the evolution basin). It was verified that the Titã's downdrift and around the Pier were successively dredged since the 1950s, in addition to the creation of the port access channel in the 1970s. The second sector is marked by presence of sandy features, highlight a longitudinal bank of about 2km². This feature presented great spatial-temporal variations since the installation of the harbour structures, corroborating with pre-existing works that point out that the bank already existed before the port installation. The genesis of the bank is associated to the morphodynamic effect of the Mucuripe headland and the relative sea level rise in the Holocene. Four rocky complexes were found, as follows - Meireles, Grande, Pedra do Justin, and Velha. At the end of sector two, there is the outfall with about 3 km in length and a sector of dredged sediments disposal. This sector is partially modified by the port structures. It can be verified that the morphology of the submarine coast of Fortaleza shows great modifications (deepening of the bed) near the Mucuripe harbour and in the coastline, due to the rigid structures of protection and port management.