Soap Creek Valley
How one thesis put spoken memories beside survey notes, maps and air photos.
Soap Creek Valley, Benton County, Oregon (mostly Township 10 South, Range 5 West, Willamette Meridian)
“What did the forests of Soap Creek Valley look like before anyone alive could remember, and how can anyone know?”
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Soap Creek Valley is a valley of about 15,000 acres a few miles north of the Oregon State University campus. In his 1999 thesis, forest historian Bob Zybach asked whether the memories of people who lived and worked there could reliably document how its forests changed, and he checked their accounts against land surveys, maps and aerial photographs. This page is a short tour of how he combined them: more about the method than the answers.
What the record shows
Soap Creek Valley drains an eastern slope of the Oregon Coast Range. It lies in northwestern Benton County, along the southern border of Polk County, and covers about 15,000 acres.
“Soap Creek Valley drains an eastern slope of the Oregon Coast Range in northwest Oregon.”
Source: Zybach 1999, p. 6
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The foundation of the study was living memory: recorded interviews with people who knew the valley first-hand. Their memories also helped interpret, check and even find the other records.
“Living memory is the principal, and foundational, data source used for this study and was a critical element for interpreting, corroborating, and/or locating other sources of data.”
Source: Zybach 1999, p. 21
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Table 4 of the thesis profiles 17 people whose memories were recorded, 5 women and 12 men, born between the 1890s and the 1930s: farmers, ranchers, loggers, foresters, sawmill workers, a botanist, a firefighter and a wildlife specialist.
Source: Zybach 1999, p. 39 (Table 4; this page names none of them)
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The oldest people were interviewed first whenever possible, because they held the earliest and most fragile memories of the valley. The thesis is open about this being a deliberate bias.
“Older participants were given priority and interviewed first whenever possible. This precedence, or bias, was considered worthwhile because the oldest members of potential interviewees held the earliest and most fragile memories of Soap Creek Valley.”
Source: Zybach 1999, p. 36
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Interviews were often held at the very places where events had happened, and maps, aerial photographs, sketches, prehistoric tools, even broken glass, old bricks and nails were brought along to jog memories.
“In order to facilitate recall, interviews were often conducted at locations in which specific events had transpired”
Source: Zybach 1999, pp. 46-47
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Every interview was recorded and typed into a transcript. When a document later showed a date was wrong, the transcript was corrected and a note added, while the tape kept what was actually said. In the transcripts, written records take priority over memory.
“The recording can always be used to determine exactly what was said, and the oral historian can safely quote transcribed text with assurance that historical documentation is given priority over human recollection.”
Source: Zybach 1999, pp. 43-44
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Memories can be mistaken, so each account was checked against other scientific and documentary sources, a cross-check the thesis calls triangulation. In most cases the accounts agreed in striking detail, whatever the speaker’s age, schooling or line of work.
“In most instances, corroboration demonstrated striking degrees of consistency in detail regarding descriptions and interpretations of forest cover change, no matter the ages, academic achievements, or occupations of the various observers”
Source: Zybach 1999, p. 59
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The original land surveys describe the forest before living memory begins (the 1890s), before the first timber cruises (the 1910s) and before aerial photographs (the 1930s). They also help check later photographs, cruises and people’s memories.
“Land Surveys provided valuable information regarding forest cover patterns that preceded living memory (1890s), timber cruises (1910s), and aerial photographs (1930s).”
Source: Zybach 1999, p. 21
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Aerial photographs cover the valley from 1936 onward, ten or more sets of them. The thesis calls a series like that the surest and most detailed way to compare the same ground over time, and the photos doubled as prompts in interviews.
“Continuous series of aerial photographs provided the surest, most reliable, and most detailed form of repeat photography (Progrotskie 1974; Gruell 1980; Skovlin & Thomas 1995) used for this study.”
Source: Zybach 1999, p. 19
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Putting the evidence together, the thesis describes the valley in 1826: most trees were less than 50 years old, and most land was bunchgrass and white oak savannah.
“Most trees were less than 50 years of age, and most land was bunchgrass and white oak savannah.”
Source: Zybach 1999, p. 208
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The thesis names the spread of Douglas-fir into the grassy prairies and oak savannah as the most widespread change in the valley’s tree cover in historical time.
“The expansion of Douglas-fir into the grassy prairies and oak savannah of Soap Creek Valley has been the most widespread change in horizontal and vertical forest tree cover patterns to occur during historical time”
Source: Zybach 1999, p. 111
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A headline conclusion: people have been the main shapers of the valley’s forest cover for the past 500 years, and likely for the past 10,000 years or more.
“Humans have been primary shapers of Soap Creek Valley forest cover patterns for the past 500 years”
Source: Zybach 1999, p. 209
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What the record can’t say
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- Gap in the record This page summarizes the thesis; it does not reproduce the interviews. OSU Special Collections describes the published oral histories, and the thesis says the original tapes went to the Oregon Historical Society.
- Gap in the record The thesis describes the valley as a whole. It can’t tell you what grew on one particular parcel; that takes the parcel’s own survey notes, photographs and people.
- Gap in the record The thesis quotes very little of the surveyors’ own wording. The typed copies of the field notes it used are on file with the Benton County Surveyor’s Office.
- Gap in the record A few dates in the thesis are given two different ways in different places (the date of a storm, the year a town was disbanded, the year a sawmill camp opened). This page leaves those out rather than guess.
- Gap in the record The thesis also discusses the people who lived in the valley before 1826. That history is not summarized on this page; the tribes’ own cultural offices are the place to start.
What to look up next
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Now try your own place Bring boots; the corner posts won’t come to you.