Dinâmica de sedimentos e granulometria em ambiente semiárido

• Ano de defesa: 2019
• Autor(a) principal: Silveira, Paulo Roberto de Souza
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Granulometria; Modelo de Foster; Bacia do Pentecoste; Semiárido; Size grain; Foster model; Pentecost basin; Semiarid
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/42578

Granulometry is one of the main factors affecting the sediment dynamics in watersheds, from their detachment from the soil to the transport or deposition along the slopes, in the drainage and reservoir network. The objective of this work was to analyze the sedimentation behavior of sediments in a small Brazilian semi-arid basin, in the Caatinga biome, from the slopes to the exudation, and to elaborate a simplified method to estimate the sedimentation standard of sediments in a basin, as well as the dynamics granulometric in reservoir. The study was carried out in the Pentecost basin, located in the semi-arid region of Ceará. The experimental part of the research was carried out in the Curv Valley Experimental Basin (BEVC) with rainfall and hydrosedimentological data collection, soil samples from the catchment basin, daily precipitation and surface runoff during the rainy season between 2015 and 2017. For a historical series of precipitation, the CN-SCS model was applied for the estimation of synthetic series of flows to the School Water, located in the exudate of the BEVC. Sediment detachment models published in the literature were tested and applied to the study area. Based on actual data, an estimate of the sediment transport pattern was made by the basin. In the reservoir, the transport models proposed by Haan et al. (1994) and Fifield (2011) developed in Fortran program. After calibration of the data and analysis of the results in comparison to the actual data of sediment granulometry at specific points in the BEVC reservoir, the model was applied to a sample of reservoirs in the Pentecoste basin. Fourteen sub-basins were chosen for the application of the methodology proposed in the BEVC. The physical analysis of the soils collected was performed with and without dispersant use. The results showed that the slope sediment detachment model proposed by Foster et al. (1981) presented the best results compared to the others, with a Nash and Sutcliff (NS) coefficient of 0.99, under mixed vegetation cover. There was an enrichment of the clay and silt components, of the order of 5 and 13, respectively, and decrease of the sand concentrations, 0.4, between the sediments contained in the matrix soil and those present in the inflow to the reservoir. The model of Fifield (2011) for sediment transport in reservoir presented reasonable accuracy when the model data were compared with granulometric data from the interior of the reservoir. When the models, detachment, transport in the basin and the reservoir were applied in a dense network of reservoirs, 7 of the 14 reservoirs presented acceptable results, according to the calculated NS coefficient, and the others classified as unacceptable. It was also found that the semi-arid reservoirs have high sediment retention efficiency.