The Madeira River Waterway is an important transportation link between the agricultural production areas of western Brazil and the deep draft ports on the Amazon River, where commodities are transferred for domestic consumption or international export. However, navigation reliability is limited, especially during low-flows. In addition, current economic studies predict that the demand for the waterway is expected to increase, especially for agricultural commodities. A primary impedance to navigation on the Madeira River is sand shoals in thalweg crossings, especially near split flows at islands. These bottlenecks in the system require navigators to light-load their barge convoys to tonnages less than 25% of loads transported during high water levels. A secondary impedance is associated with rock outcrops near the navigation channel, which combined with a lack of aids to navigation, increase risks of accidents for the convoys.
To address navigation reliability and safety, a planning study framework has been developed on the Madeira River. This framework aims to design alternatives that will provide economically justifiable engineering solutions for improved waterway reliability and reduced navigation risk (safety) during low flow conditions. The planning study implements the USACE 6-step planning process, which includes identifying navigation opportunities; forecasting future navigation conditions; and formulating, evaluating, comparing, and ultimately selecting a recommended plan. The planning study evaluates alternatives consisting of maintenance dredging, rock excavation, river training structures, and bank stabilization using engineering tools that were developed to assess design effectiveness. Alternatives were analyzed by combining five primary studies; namely, a statistical analysis of navigation reliability; a fluvial geomorphology study, a hydraulic model to determine low water datum conditions; development of a design barge configuration and associated channel dimensions; and a sediment transport model to evaluate channel response due to the proposed measures and alternatives.
The statistical analysis developed a framework for the determination of the navigational low water reference level. This information was used to calculate the low water reference plane in a hydraulic model between observed gage locations. The model was calibrated to known sand shoal depths under low-flow conditions as well as moderate and flood flows. The design barge configuration task was combined with a fluvial geomorphology study to demonstrate the navigability of a 3x3 barge convoy (60m long x 11m wide per barge) configurations during low-flows and a maximum of 5x4 barges during high flows. The channel alignment associated with these design barge configurations was determined to fit within the current sinuosity of the Madeira River, which does not require channel straightening in the system. Finally the sediment transport model was developed and applied to predict the future conditions associated with the proposed alternatives and to evaluate the effectiveness of dredging, river training structures, and other measures for improved navigation. The planning study analyzes alternatives that will provide the maximum cost-benefit ratio over the 50-year economic life-cycle of the Madeira River Waterway Project.