Contribuições da análise geomorfológica ao planejamento de áreas de expansão urbana da porção leste/sudeste de Teresina, Piauí, Brasil

Abstract

The accelerated growth of urban centers, which has been most intense since the middle of the 20th century, when cities became a major population attraction, has generated a series of socio-environmental problems, including those associated with surface and subsurface processes, both natural and anthropogenic, in the occupied spaces. This occupation of the terrain without adequate planning has contributed, for example, to the intensification of floods, inundations and landslides, in addition to other damages that directly interfere with the quality of life of its inhabitants. In this sense, this research has the general objective of analyzing the geomorphological compartmentalization of the municipality of Teresina, capital of Piauí, as well as the dynamics of the relief inherent to these compartments, with a view to diagnosing environmental weaknesses of areas with potential for urban occupation located in the East/Southeast region of Teresina, notably in a section that extends from the current urban perimeter to the rodoanel inaugurated in 2019. Regarding the specific objectives, we sought to: a) spatialize the geomorphological compartments of the municipality of Teresina, seeking to relate them to the geomorphodynamics in force in the East/Southeast region of the city, notably in the space between the current urban perimeter and the ring road inaugurated in 2019; b) recognize, characterize and understand the geomorphodynamic processes that should receive priority attention in urban and environmental planning in the study area; c) diagnose the environmental fragility of the East/Southeast region in the portion bordering the urban space of Teresina in order to assist public managers in decision-making and urban planning, with a focus on areas suitable for future urban expansion. To achieve the proposed objectives and obtain an integrated view of the geomorphological compartments in the face of urban occupation, a theoretical basis was used (Ab'Saber, 1969; Douglas, 1988; Ross, 1992; Miyazaki, 2017) supported by Historical and Dialectical Materialism, envisioning an environmental analysis integrated with Urban Geomorphology, based on office activities and field work, geoprocessing techniques for the elaboration of thematic mappings of physical-natural aspects, relief features, urban occupation, as well as environmental potentialities and weaknesses (Ross, 1994; Gouveia; Ross, 2019). The results show that the population of Teresina has been dealing with problems related to flooding since the early days of its settlement, when the main factor responsible for these events was the Parnaíba River, especially in the northern part of the city. According to the Saraiva Plan of 1852, settlements spread throughout the city, which also faced flooding from the Poti River, and then from the flooding of the numerous streams that flow through the city, especially in the eastern and southeastern regions and part of the southern region. The area delimited in this study as a potential axis of urban expansion has a surface model that is somewhat different from that found in the consolidated urban area, such that the northern portion is dominated by hills, with a tendency to round, and with flat-topped tables. From the central-northern portion, continuing southward, there are surfaces that have been intensely reworked by drainage, interspersed with plains and river terraces. The Topographic Wetness Index (TWI) model, which measures the capacity for moisture accumulation, and the environmental fragility map demonstrate that, if there is no action plan to coordinate occupation in this region, problems related to flooding and waterlogging, especially caused by streams, will continue to occur and others will emerge, such as frequent landslide events.