Erosão e progradação da praia de Pontal De Maceió, Fortim, Ceará

Abstract

The beach system is extremely dynamic due to the factors that controls the shape of coastal features and the position of the coastline, such as sea level variations, waves, currents, tides, sedimentary fluvial and wind input. The beach of Pontal de Maceió, located in Fortim - Ceará, is a sandy beach, characterized by the presence of a rocky promontory that limits the mouth of the Jaguaribe River. The motivation of the study is to understand the cycles of erosion and progression, considering that the beach underwent an erosive cycle from 1990 to 2013, and without engineering interventions a depositional period began. In this way, the present work aims to analyze the space-time behavior of the coastline of Pontal do Maceió relating to the particular coastal processes that occur on beaches adjacent to promontories. The methodology consisted of bibliographical, cartographic and field surveys. The acquisition of images of the Quickbird and Rapideye satellites from the years 2004 - 2014 was performed for space-time variation of the coastline through the DSAS 3.2 extension. While the short term monitoring was done through the field activities in the months of April, August and October of 2017 in which the positioning of the coast line was recorded by RTK walking, sediment samples was collected and 4 beach profiles were made through RTK and total station. In addition, the parameters - waves (Hs, direction), discharge of the Peixe Gordo Dam and precipitation data of the Aracati station were evaluated. Through the spatio-temporal variation of the coastline of Pontal do Maceió it is possible to distinguish two different periods that mark the alternation of an erosive cycle to a progradant. Erosion of -0.02 m / year was observed in the period from 2004 to 2013. Already from 2013 an accumulation of sediments and the elevation of the altimetric quota of the post-beach were observed. The segment's development is possibly associated with the dynamics of the sandy banks adjacent to the Jaguaribe river that are eroded and carried by the coastal drift. On the left side of the mouth of the Jaguaribe river, the erosive tendency was -8.6 m/year. Systematic monitoring is necessary due to the high vulnerability of the beaches adjacent to river mouths, since they are very important information for the management of the coast. These data are extremely useful for simulations through mathematical models of seasonality and predictions of global climatic phenomena.