Landsat-based analysis of mega dam flooding impacts in the Amazon compared to associated environmental impact assessments: Upper Madeira River example 2006-2015

Hundreds of dams are currently under construction or have been built in the Brazilian Amazon with the purpose of fueling social development via hydroelectric power and the transport of goods along rivers. However, many times the environmental impact assessments used to approve these projects have omitted or grossly underestimated the impacts of these dams, leading to severe and often irreparable damage. As such we conducted a case study of the Santo Antônio and Jirau mega dams on the Madeira River in Rondônia, Brazil and used Landsat TM and OLI data to determine area covered by water along a 539 km stretch of the Madeira River from 2006 to 2015 (covering before and after the dams' construction). The classification method used in this study was modified based off of previous methods and provided a highly accurate water classification suggesting it to be a valuable way of accurately classifying water along with other land cover classes. We compared the water areas calculated from Landsat land cover maps to the environmental impact assessment estimations used to approve the dams' construction. This analysis showed the reservoirs to be at least 341 km2 (64.5%) larger than predicted with an additional 102 km2 of unpredicted flooding outside of the planned reservoir areas and 160 km2 more natural forest flooded than expected.