What would we see if we looked in the distant past of a river's history? We know that the path and boundaries of any waterway will change over the span of thousands of years, but the reality may be more surprising than you think. Aided by lidar, an aerial laser radar technology, cartographer Daniel Coe produced this ghostly blue map of data showing the historical paths of the Willamette River in Oregon, spanning 15,000 years.
Seen over at This Is Colossal, the idea of rendering a river's historical path is nothing new. In the 1940s, Harold Fisk was commissioned by the Mississippi River Commission to map out the whole Lower Mississippi Valley, generating these breathtakingly meticulous and beautiful maps of slow, snaky riverine progressions through millennia. It was a "great leap forward in understanding the alluvial and sedimentological processes of the Mississippi Valley and the fundamental value of these insights to river engineering strategies and techniques."
With the modern version of the Willamette River by Coe, the idea is the same, but the latest technology is used. Lidar, which has been said to be either an acronym for "Light Detection And Ranging," or as a portmanteau of "light" and "radar," is a remote-sensing technology that relies on shooting millions of laser points to the ground, generating data that is collected by low-flying aircraft. Using this data, an accurate model of the ground can be produced. Lidar has been used to map global forests, orient self-driving cars, and can even warn cyclists of oncoming cars. That's how this image, which is available as a poster, was made, says The Oregonian:
It is possible to strip buildings and vegetation from the images, so that only the ground is shown. In the Willamette River poster, the shades of white and blue show elevations. The purest white color is the baseline, (the zero point, at the lowest point near Independence on the upper part of the image). The darkest blue is 50 feet (or higher) than the baseline.
The shades of white show changes in elevation, between 0 to 50 feet. This brings out the changes made by the river channel in the last 12,000 to 15,000 years, in the time since the landscape was basically swept clean by the Missoula floods.
To orient yourself, this portion of the Willamette flows past Albany (near the bottom), going north toward the towns of Monmouth and Independence near the top. The Luckiamute River flows into the Willamette from the left side, and the Santiam River flows in from the right.
This modern data-driven map bears some resemblance to the hand-charted riverine maps of old. But there's an aliveness to it, thanks to the many more points of data used. Coe, who created the map for the Oregon Department of Geology and Mineral Industries (or DOGMI, which has been collecting lidar data since 2006), remarks:
The different movements of the river make the image take a liquid shape, even almost like a cloud of smoke. This shows the magic of lidar.
These images remind us that the body of a river is a living, moving thing, meandering along long-forgotten passages. They also remind us how fleeting our human lives are in the 'big picture' of slow, but dynamic, geological forces. What we see seems so static, so permanent, yet the reality is that all living things change, whole landscapes transform, if given enough time.
For more information, visit DOGMI, The Oregonian, or check out the poster (free download). If you are in the area, you can purchase a real copy of the poster for $15 here: Nature of the Northwest Information Center [info deleted].
UPDATE: The Nature of Northwest Center has closed. The poster is downloadable for free (see link above), but there are still some hardcopies of the poster left, though. If people are in Portland, they can contact Ali of DOGMI via email to pick one up: ali.hansen [at] state.or.us