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A High-Tech Search for Archaeological Sites in the Southern Willamette Valley
A High-Tech Search for Archaeological Sites in the Southern Willamette Valley

Portland State University graduate student Tia Cody is combing through a 234,000-acre swath of the southern Willamette Valley in search of mounds. For Cody, whose advisor is anthropology professor Shelby Anderson, the project is the focus of her thesis research. Working in collaboration with members of the Confederated Tribes of Grand Ronde, Cody is developing high-tech tools to locate archaeological sites in an area in which bands of the Kalapuyan people once lived.

According to Cody, there are fewer than thirty adequately recorded mounds within the survey area, and yet, there are thought to exist as many as four hundred. The mounds, which may have been places of habitation, refuse deposits, or even burial sites, are of cultural and historical significance to members of the Confederated Tribes of Grand Ronde, some of whom are descendants of the Kalapuya people.

Locating potential archaeological sites within the Calapooia watershed, however, presents some challenges. For one, the area Cody is exploring, at 234,000 acres, is far too large for a typical archaeological survey. The terrain varies from farmland and floodplain in the west to coniferous forests and rugged mountains in the east. Further complicating the search for these elusive mounds is the fact that the vast majority of the land in the watershed (94%) is privately owned and may not be accessible to archaeologists deploying traditional survey methods.

To overcome some of these challenges, the Confederated Tribes of Grand Ronde proposed using a set of tools gaining traction among some in the archaeological community. They shared their proposal with Anderson and Cody, who agreed to take on the project as the focus of Cody’s thesis research. Using LiDAR (Light Detection and Ranging) data obtained from the Oregon Department of Geology and Mineral Industries, remotely sensed infrared imagery, and aerial photography combined with a Geographic Information System (GIS) interface, Cody began developing a generalizable model that, if successful, will enable the use of computational analysis to identify mound sites within the watershed. Various iterations of the model utilized analysis of aerial photography and infrared imagery to search for the mounds but provided inconsistent results. Turning to the LiDAR data, Cody was able to analyze the shape and slope of known mounds and optimize the model to search for similar forms and features within the dataset. When tested with the LiDAR data, the model was able to identify roughly 40% of the previously known mounds in the survey area. By further exploiting the data and manipulating the model’s parameters, Cody thinks she can improve upon those results, which could significantly increase the chances of discovering new mounds within the Calapooia watershed.

In the next phase of the work, Cody plans to flip the LiDAR data on its head, rendering an inverted topological map of the watershed in which features such as mountains, hills, and even mounds become sinks. By adjusting the model to search for depressions with characteristics similar to known mounds, Cody hopes to improve its ability to identify both known and unknown archaeological sites.

“If the model succeeds,” Cody said. “We might be able to identify locations where we can say, ‘There’s a strong chance this site is of cultural and historical significance.’ And because the model is generalizable, it could prove useful in the search for archaeological sites in other locations that have been scanned using LiDAR.”

Combining LiDAR data and computer modeling into a tool for conducting archaeological surveys is an innovative practice, and is one that is gaining traction at sites in Italy and across Central America. While it is still catching on in the US, Cody thinks it could have a significant impact on how archaeologists search for clues about the cultures and civilizations of people who came before us. Cody plans to present the work to members of the Confederated Tribes of Grand Ronde and provide them with the tools she’s developed. If successful, the model could help other archaeologists and members of the tribe identify and preserve culturally and historically significant sites across the southern Willamette Valley.