Nebraska Soils Field Trip - Virginia Tech

4th IUSS Soil Classification Conference Field Tour Guidebook
Site 2a – Onawa Series
One of the soils we will observe at the Hitchcock Nature Center is the Onawa series taken from
the Missouri River flood plain. We collected the soil profiles and transported them to this
location to save time during the tour and avoid possible flooding. Onawa soils are very deep,
somewhat poorly drained soils on flood plains. These soils formed in clayey alluvium over loamy
alluvium. The loamy materials in the lower part of the profile represent the source materials for
the loess hills formation at the Hitchcock
Nature Center.
Flooding on the Missouri River in in 2011 lasted
from May through August along much of its
reach closing roads, major highways, railways
disrupting transportation around the region. At
right, an aerial photo of the Interstate 29 and
Interstate 680 intersection shows the extent of
the flooding across the valley.
When the floodwaters receded, I-29 and I-680
interchange was not structurally damaged and
was reopened, but thick silty deposits covered
the road and right of ways the kill zone due to
inundation is evident on the overpass
embankment (center).
Upon drying, the silty sediments were again
susceptible to the wind erosion and are carried
eastward into the Hitchcock Recreation Area
(below). The flooding, sedimentation, erosion,
and deposition cycles that created the Loess Hills
of western Iowa clearly continues today.
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