Dinâmica do uso e ocupação da terra e os alagamentos e enchentes na bacia do arroio da Ronda em Ponta Grossa (PR)

Abstract

The use and occupation of land is a theme studied in depth in geographic science, because it is a subject that aims to demonstrate the spatial changes caused by countless human activities. The process of intense soil waterproofing in urban areas consists of a significant modification, since it contributes to an increase in the runoff of rainwater, which if not conducted and treated in an efficient and sustainable manner they can cause episodes of overflow and floods. In this context, the Ronda stream watershed in the city of Ponta Grossa (PR) is the object of study, because over the years there have been occurrences of floods causing numerous losses to the local population. The stream of Ronda watershed occupies the southwestern portion of the urban perimeter of the municipality of Ponta Grossa, in the state of Paraná, with a total area of 34,43 km². The springs of the stream are located in a densely urbanized area and its mouth on the Tibagi River. For the research, the time frame used refers to the years 1980 to 2017. The area of the Ronda stream watershed showed a diversified land use dynamics over the 37 years analyzed, where urban density has replaced areas of native vegetation and fields. During this period, 60 occurrences of overflow and floods were recorded. Therefore, the central question of the research was to understand how the transformations of land use and land occupation in the watershed of stream can influence the increase in runoff. The general objective was to understand the relationship between overflow and floods episodes in the watershed and the increase in runoff from different land uses and occupations between the years 1980 to 2017. The hydrological model Curve Number (CN, SCS, 1972) was used, which considers the combination of land use and occupation variables and physical data (soil types), to demonstrate and spatialize the areas most susceptible to the generation of runoff. The vast majority of occurrences are located in the northwest and northeast portions of the watershed, close to water courses and in areas with low declivity (0 to 8%). The results showed that land use partially influences the occurrence of overflow and floods, especially when associated with the replacement of areas of native vegetation and fields by urbanized and waterproofed areas. However, the physical characteristics of the watershed, such as the low slopes and soil types, showed a strong influence for the occurrence of these phenomena.