Geoestatística aplicada à análise da distribuição de chuvas intensas no Estado do Ceará

Abstract

Intense precipitation can causes several impacts on the socio-economic structure, such as: floods, landslides, material damage and loss of human lives. Therefore, it’s essential to develop research that promotes knowledge of the spatial and temporal distribution of rainfall, aiming at land use planning and assisting in hydraulic works, essential in water management in the semi-arid region. In view of this, in the characterization of extreme rainfall events, the Intensity-Duration-Frequency (IDF) curves or equations are used, which establish the magnitude of rainfall for a specific recurrence period, duration and location. For Ceará, no studies were found that analyze the spatial variability of intense rainfall, a gap explored in this research. Thus, the objective of this work was to analyze the spatial distribution of heavy rainfall in the state of Ceará by applying geostatistical techniques. For that, intensities were calculated by means of the IDF equations developed by Batista (2018) using the isozone method and, subsequently, a geostatistical study was conducted using the R software, with the gstat package and the QGis software. An exploratory analysis was performed followed by a variational analysis, modeling the experimental semivariogram and fitting the spherical, exponential, and gaussian models. The model that presented the best fit, by cross-validation, was applied to the mapping process by ordinary kriging or universal kriging. It was found a good performance of the geostatistical techniques in the mapping of heavy rainfall in the state of Ceará, with emphasis on the exponential theoretical semivariogram model that stood out in most of the events analyzed. It was found that the regions of Cariri, Centro Sul, south Vale do Jaguaribe and Sertão Central presented the highest intensities in the short duration intense rains (5 minutes), while the regions of the coast, especially Grande Fortaleza, Litoral Leste and Litoral Norte stood out for the rains of longer durations (240 minutes). The regions of the Sertão de Canindé, south of the Maciço de Baturité, north of the Sertão Central and especially the Vale do Curu/Litoral Oeste, presented the lowest intensities in the analyses performed. Therefore, it was possible to present a broad perspective on the spatial distribution of heavy rainfall events, verify the existence of spatial dependence and identify critical areas with respect to their occurrence.