Estimativa da descarga sólida de sedimentos em um trecho do Rio Caí - RS

Abstract

The hydrosedimentological cycle encompasses several stages ranging from formation, erosion, transport and eventually deposition of sediments with water as the main transport agent. There are several factors that influence the cycle, being the anthropic actions that cause the greatest impact, especially in soil erosion. In Brazil, several sediment monitoring stations are set up in the territory, but still precise measurements are needed in order to obtain more specific data. To help predict the behavior of water bodies, there are tools that model stages of the hydrosedimentological cycle, such as the HEC-RAS software. The objective of this work was to estimate the total solid discharge and to identify the sediment deposition zones of a section of the Caí River, for which samples of field materials were collected from both suspended and bed sediments. With this information, a simulation was performed using three different sediment transport functions, Yang, Ackers-White and Meyer-Peter and Muller, with the help of HEC-RAS software. The granulometric analysis indicated that the river bed is a bed formed predominantly by gravel. The software modeling results showed that the Ackers-White function best reproduced the deposition patterns as indicated by the previously available topo-bathymetric survey. The Yang function showed a greater erosion of the bed than the others, especially in the center of the channel. Meyer-Peter and Muller were the function with the results that disagree with the others indicating a zone with deposition of more than 3 m. The modeling of suspended sediments demonstrated a much greater similarity of results between methods than bed discharge. For future work, it is suggested that new field surveys be made, such as a new topo-bathymetric survey and new collections of suspended sediments (sic).