Peruvian Amazon Waterway Project: River Dynamics and Shallow Zones

The Peruvian Amazon Waterway (PAW) project aimed to strengthen commercial transport between Brazil and Peru. The PAW project involved the meandering (Huallaga, Ucayali) and anabranching (Marañón, Amazon) rivers, with designed channel specifications such as a minimum water depth of 2.44 m and channel width ranging from 44 to 56 m. Regions with water depth smaller than 2.44 m are called shallow zones (SZs). A detailed environmental impact assessment (EIA) study was carried out using 14 SZs (dredging 3.87 million m3 of sediments). Simultaneously, in 2018, the definitive engineering study (EDI) described 35 SZs, indicating a dredging volume of 11.03 million m3 of sediments [including an overdredging to ensure a depth of 3.05 m (10 ft)]. Comparing the EIA and EDI studies, the number, location, and recommended dredging volume of SZs have changed significantly (the biggest change in SZs was along the Ucayali River: EIA, 4; EDI, 24), revealing a lack of understanding of river dynamics. This study introduces the morphodynamic index (MOR), a remote sensing-based method to classify river activity into low, medium, and high categories by analyzing median activity values and percentiles. The meandering Huallaga and Ucayali Rivers are dominated by segments under medium and high MOR indexes, while for the anabranching Marañón and Amazon rivers, most of the segments are under low and medium MOR indexes. The flow field structure at low, medium, and high MOR indexes reflects that secondary cells and over in medium- and high-MOR index regions (meandering) than in low-MOR index regions (anabranching). A significant correlation between the MOR index and SZ reflects that under medium and high MOR indexes, the spatiotemporal variability of SZ occurrence is clearly defined by the planform morphology.