Unsteady Sediment Transport Model of the Lower Tapajós River

Código

ENES20200002

Autores

Calvin Creech, Renato Souza Amorim

Tema

01 - PROCESSOS HIDROSSEDIMENTOLÓGICOS E MORFOLÓGICOS EM BACIAS HIDROGRÁFICAS

Resumo

The Tapajós River is an important fluvial system in the Amazon basin, contributing to the ecological, transportation, recreation, and economic functions in the region. The lower 330km of the Tapajós River is extensively used for shallow-draft inland transportation of commercial commodities (primarily agricultural). In support of a navigation improvement project, the sediment dynamics of the lower Tapajós River were analyzed in a one-dimensional sediment transport model in HEC-RAS. The influence of the Amazon River backwater on the hydraulics of the system limits the opportunities to model the sediment dynamics in a steady or quasi-unsteady environment. Therefore, a fully unsteady sediment transport model in HEC-RAS was completed for this system. Significant deposition of sediment occurs in the lower 175km of the Tapajós River in a deep and wide fluvial ria feature, which has been aggrading since the Last Glacial Maximum (LGM), when ocean levels were approximately 120m lower than present day. The unsteady sediment transport model was compared to two sediment cores, which had previously been analyzed for chronology. The sediment transport model simulated the previous 20 years of behavior and resulted in sedimentation between 0.043m and 0.103m over this period, compared to a range of 0.056m to 0.13m of sedimentation based on the cores. This model will be used to estimate future sedimentation rates associated with channel dredging projects throughout the Tapajós River as well as providing opportunities to analyze the influence of anthropogenic development within the basin.