Classificação tipológica ambiental das falésias costeiras do Estado do Rio Grande do Norte (RN), Nordeste do Brasil

Abstract

The potiguar coast has several environmental systems, such as dunes, beaches, rivers, estuaries, lagoons, and cliffs that integrate the coastal area of the state of Rio Grande do Norte (RN). The sea cliffs are important indicators of the environmental changes that occurred in the Quaternary period, and, because they are unique natural monuments, they were selected as the object of study of this thesis, which its general objective is to perform the typological classification of coastal cliffs in Rio Grande do Norte. The justification for carrying out this research is based on the premise that although some specific works have already been carried out on the RN’s cliffs, describing their environmental conditions, and reporting some problems related to the use and occupation of the soil, none of them dedicated themselves to conducting a classificatory analysis of this morphological feature. Thus, performing this work implies filling this gap. As for the social relevance of this research, it is in the identification of the environmental situation of the cliffs. They are landscape inheritances which safeguard the marks not only of physiographic and biological processes, however they are also the collective heritage of the people from Rio Grande do Norte. The relevance of identifying the environmental situation of the cliffs is in the fact that they are landscape elements of great scenic beauty, although, paradoxically, they have great environmental fragility, due to their genetic, stratigraphic, and morphological characteristics. In addition, the occupation of the coastal region of Rio Grande do Norte, similar to other Brazilian states, has been occurring irregularly. It does not respect the limits defined by the resolutions of the Conselho Nacional do Meio Ambiente (CONAMA). The resolutions were standardized in 2002, and define the use and occupation of coastal areas, particularly on escarpments with a slope greater than 45°. That said, this work starts from the hypothesis that the classification of potiguares cliffs can be carried out according to their natural characteristics and forms of use and occupation. In view of this, the qualitative methodology used was developed to be divided into three stages, namely: survey of data on the cliffs, in particular the RN; execution of field work; and elaboration of cartographic material. Having defined the cliff categories, their characterization was accomplished regarding the compliance or not with the environmental legislation that deals with the environmental conditions of use of these features to identify the resulting environmental impacts. The results indicate the existence of 5 (five) types of cliffs classified according to the shape of the escarpments (horizontal stratification, stratigraphic discontinuity, convex cliff, protruding cliff and irregular escarpment); and some subclasses defined based on the integration of criteria such as lithology, morphodynamic situation, vegetation cover and influence of climatic subtypes. Some other features were also identified, they were: a ruiniform feature supported by eolianites; abrasion terraces modeled on the Barreiras Formation; and arches made of ferruginous sandstones. Therefore, from the information produced in this doctoral work, it is possible to conclude that there are environmental impacts generated by the non-compliance with the use and occupation laws of the cliffs and that this non-compliance, added to other natural factors of the RN cliffs, make them represent a risk, which makes the existence of the proposed classification a tool for drafting more specific and effective laws and thus preventing accidents.