Coupled sediment yield and sediment transport model to support navigation planning in Northeast Brazil.

摘要

Deposition of sediment (shoaling) in commercial waterways is a major obstacle to maintaining sustainable riverine transportation of bulk goods (primarily agricultural and mining commodities). The rate of aggradation of sediment in a waterway is directly related to both the rate of sediment erosion from upland and river bank sources (sediment yield) and the energy in the river to effectively transport the sediment through the waterway system (sediment transport). Historically, methods used for waterway development have included trial and error or rules of thumb associated with river training structures and chute cut-off canals or engineering of navigation locks and dams. More recently, hydraulic and sediment transport modeling techniques have been developed and applied in designs of specific waterway development features within discrete reaches of a system. However, previous large scale waterway development planning has not incorporated both the sediment yield and sediment transport modeling necessary to develop engineering solutions based on a comprehensive understanding of the inter-related sediment dynamics of the system under both current and planned future conditions.;To advance waterway development planning, this research developed a coupled sediment yield and sediment transport modeling framework. The coupled sediment modeling approach was applied within a case study in a waterway that is being developed in Northeast Brazil - the Sao Francisco River waterway. A Soil and Water Assessment Tool (SWAT) sediment yield model was developed and linked to a Hydraulic Engineering Center -- River Analysis System (HEC-RAS) sediment transport model to develop a feasibility study of navigation improvements on the Sao Francisco River. A geomorphology analysis was performed to segment the geomorphological conditions leading to shoalings amongst nine reaches in the waterway. The coupled modeling was leveraged to develop river training structure conceptual designs, which were compared against long-term dredging solutions to find an economically feasible and sustainable navigation channel. The coupled sediment yield and sediment transport modeling framework demonstrated in this research can be applied to gain the necessary understanding of the sediment dynamics of a system for better decision support in the area of navigation planning in other waterway development projects.