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"Natural features divide the McKenzie watershed into three general regions the
High Cascades, the Western Cascades and the Willamette Valley.
The High Cascades form the easternmost portion of the watershed. Geologically
young, this high elevation area (above 6,000 feet) has heavily glaciated
volcanic peaks reaching above 10,000 feet with lava flows and many small and a
few large lakes formed by glaciation.
Most of the McKenzie watershed west of the High Cascades lies 
within the
Western Cascades region. Geologic features in this region are older than the
High Cascades, consisting of deeply dissected volcanic mountains (below 6,000
feet) that rise abruptly from the Willlamette Valley. Steep ridges in this
region generally run east-west, steadily gaining elevation towards the east.
The westernmost portion of the watershed (near Springfield) is in the
Willamette Valley region, a broad, level to gently sloping area of bottomlands
and terraces formed from alluvial deposits. The elevation in this region is low,
around 430 feet in the metropolitan area."
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