Cartography of an Oregon River

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Charting the waters of the ocean or the delicate contours of a continent seem to be the jobs of the ancient explorers and mariners who first came upon the many mysterious corners of the Earth. They were the first to invent navigational techniques we still use today; they were the first to build ships that could sail up a river to the next village or across entire oceans with no land in sight on the other side. These explorers weren’t the only ones looking for answers in the world’s waterways, though. Modern day researchers around the world are continuing to chart waterways to determine how they used to flow, how much water flowed through them, and where they led.

Rivers don’t always change their course because of a cataclysmic event like a flood or landslide. Most rivers change gradually, over many centuries. Changes can be so gradual that the rivers change almost without anyone noticing, but have a dramatic effect on the surrounding landscape of the area. Slow and steady changes are what interest cartographers like Dan Coe, who mapped the geological changes of the Oregon River.

Dan Coe utilized a geospatial technology called LiDAR. LiDAR involves collecting data using laser pointers attached to a slow and low flying aircraft. These millions of laser points can map changes in the geography of an area, showing what used to be there many years ago.

Geologists and mapmakers have come up with new ways of mapping rivers for hundreds of years. In the 1940s an effort was made to map the changes of the Mississippi River by Harold Fisk. Harold Fisk harnessed the technologies of his day and was able to produce 15 maps that showed 20 different paths that the Mississippi River had taken in the past.

Today cartographers can use technologies like LiDAR to depict the movement of a river in high resolution and in more detail than ever before. Vegetation and buildings can be removed from the image so that only geographical data is shown. Dan Coe’s map depicts elevation in terms of color, using white to show the baseline measurement and blue to depict elevation up to and higher than 50 feet above the baseline.

Using this method Coe was able to track changes in the Oregon River back 12,000-15,000 years. The map is available in print form and online from the Oregon Department of Geology and Mineral Industries.

f-poster-WillametteStreamChannels

References

Art Meets Cartography: The 15,000-Year History of a River in Oregon Rendered in Data by C. Jobson, November 25, 2015, Colossal

Dogami LiDAR Landscapes – Willamette River Historical Stream Channels Poster – Oregon Department of Geology and Mineral Industries.

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