Most of the Amazon Basin is flat, very flat. How flat? Flat enough that the Rio Solimões and Rio Negro flow languidly beside each other for about 30 miles past their confluence, in the famous Wedding of the Waters near Manaus.
The slope of Amazonian rivers is remarkably flat even hundreds of miles upstream, closer to headwaters areas, as I was reminded when trying to understand this pair of photographs, which I noticed this morning on the Rondônia, Minha Querida Rondônia page on Facebook.
Group administrator Dacosta Dacosta shared these, with the caption "Ponte EFMM de Mutum Paraná, em duas épocas" (Madeira-Mamoré Railroad bridge at Mutum Paranà, in two different periods).
My first instinct was to look for the bridge on Google maps, based on the place name he used. There is an interesting difference between the map version and the satellite version of the map right now; the map has not caught up with this inundation, even though it seems to be more or less permanent.
|Both images, Google Maps as accessed October 19, 2022|
The main indication that this is a permanent flood -- indeed, an anticipated flood -- is that a causeway and bridge were built for the BR-364 highway, where nothing more than a culvert is present on the map version.
I assumed that this related to hydroelectric projects that were completed about a decade ago -- none were present during my first three visits to the area, but I did see the Santo Antâo dam when I returned in 2019. My master's thesis involved finding dams of various sizes on aerial photographs and satellite images, so I assumed searching the area of the lake that now contains Rio Cutia would be simple. I looked over this area, to no avail:
Back I went to Google. This time I searched for the Mutum Paraná and the word "usina" for hydroelectric plant. I remember the word from visiting and researching Usina Samuel on the Rio Candeias years ago. This led to an article about Usina Hidrelétrica de Jirau, which fortunately includes geographic coordinates -- 9°15′51.8″ S, 64°38′30.8″ O. Realizing that O is for Oeste, I searched for this lat/long, changing the last character to W, and found the Jirau hydroelectric.
|Usina Jirau, Google Maps accessed on|
October 19, 2022
Zooming out, I could see that this is nowhere near the inundation that first got my attention. In fact, it is about 60 kilometers (35 miles) downstream -- with many miles in between where the Madeira (the Amazon's longest tributary) seems to be within its normal banks.
The engineers who build the dam, however, know exactly how flat this land is, and they used Geographic Information Systems to figure out where the floods would be and what steps they would need to take in order to protect the BR364 highway as it passes over what was previously a trivial tributary, many miles from their main project.
During my first visit to Rondônia (Brazil's 26th state) in 1996, I saw the first internet server while it was still in a shipping box. For years after, my (now outdated) Rondônia Web page was the only online English-language resource about the place. Now it is a place full of very connected people of all ages, and this particular Facebook group has almost as many members as the entire state did in 1960. This page is similar to many groups pages I find in U.S. communities, brimming with nostalgia.