Alterações morfológicas e capacidade de suporte ambiental da lagoa costeira do catú, Aquiraz, Ceará, Brasil

Abstract

Hydric resources using in it most different ways have been causing serious negative impacts for its depots, not only in its water exploration, but also in its borders occupation. Catú coastal lake is located in the city of Aquiraz, Ceará, and it’s characterized by elevated scenic beauty, touristic attractives and increasing real estate speculation. The incorrect occupation of the Permanent Protection Areas (PPAs) is causing a series of serious negative impacts to the lake. This research has in its base the study of the morphological alterations in Catú coastal lake in recurrence of its contribution bay using and occupation, and also verifies its environmental support capacity by using its invested sediment cargo, verifying its changes by the last ten years (2003 – 2013), by image mapping of years 2007 and 2012 for identification of using and occupation activities of the lake and its direct contribution bay, sediment contribution estimation of various economical activities and soil covering and actual and comparative bathymetry procedures in the year of 2003, sediment characterization of 49 samples of lacustrine soil, and data relation of sediment contribution and with PPAs occupation. The identified characteristics belong to the bay as a natural factor influenced area, as instanced by the region pluviometric index and the man-made activities by the borders. As for the comparing of the actual submerged relief with the year of 2003, the biggest observed alteration was the deep level with the decreasing of 2 centimeters, as well as the pointing of the deepest areas in the north of the lake, and the smallest in the medium dimension and its borders, fact explained by the constant sediment moving originated from the most different activities. By the region mapping in different years, it was verified the increasing and decreasing of several using classes in an area level. For the sediment estimate, the most contributing activities are: wildness area, deflation-planed-paleaodunic Dunes, Beach Stripe and Urban Area. As for the sediment characteristics, there is a dominance of sandy class, mostly thin sediments, followed by muddy fraction. The estuarine system has low energy by the downstream, and upward at medium portion there’s a considerable high energy. Geochemistry for the ambient has indicated low calcium carbonate values in general, with peaks in intense urban activities areas. For organic material index, the highest quantities were found by the south portion, a region with strong man-made action. It was noted the suppression of a biggest area of the PPA, being able to determine the points with more sediment contribution and geochemical cargos in areas without peculiar vegetation. Aside the environment vulnerabilities, like the floods in rainy periods, aggradations in different portions caused by urban activities with contributions for erosive process by different buildings and aggradations.