Wildlife & Habitat Loss Along the Willamette River
The Riparian Forest in the Mid-1800’s
Frequently flooded areas were largely timbered, and were
connected with the channel through flood events.
“The adjacent country [between Eugene and Harrisburg] is level…the river
bottom is from one to two miles in width…The timber, consisting of
cottonwood, maple, ash, alder, and willows, is dense, and…is traversed by
sloughs and bayous, large and small, and in times of floods is covered by
swiftly-running water to a depth of from 5 to 10 feet.” (U.S. Army, 1875)
Wooded floodplains provided habitat for wildlife- trees slowed
river flood waters, protected the land from erosion and recycled
carbon and nutrients to the floodplain and river.
“Before the Willamette bottomlands were cleared and placed under cultivation
the heavy timber and underbrush with which they were covered retarded the
water during periods of their overflow.” (U.S. Army, 1891)
Willamette
Valley
Vegetation Changes
1850
2004
“Vegetation patterns change over time under the influences of climate, succession, and disturbance
regimes. However, it appears that the array of vegetation types in the Willamette Valley has
remained relatively consistent over the last 3,000-5,000 years.”
---- “Historical Vegetation of the Willamette Valley, Oregon in the mid-1800’s” by John A. Christy, Oregon Biodiversity Information Center, and
Edward R. Alverson, The Nature Conservancy (2010).
Most riparian stands along the Willamette River, originally ranging from 1 to 7 miles wide,
have shrunk to only a few hundred feet, depending on width of the floodplain (Benner and
Sedell 1997). Many streams now have only a thin strip of vegetation one or two tree lengths
in width, and others have had all of the riparian forest removed (Hulse 1998).
Riparian and Wetland Forests
• Represented 7.2% of mid-1800’s WV
vegetation, in bands of varying width
along floodplains of larger streams and
rivers- up to 5 miles wide along the
Willamette River floodplain.
• Willow, red alder, and black cottonwood
typically occurred along active channels.
• Oregon ash, bigleaf maple, and white
oak occurred on higher terraces.
– Ash and oak were particularly important
along smaller streams where a narrow
wooded riparian corridor was bounded
by open prairie.
Riparian and Wetland Forests
• Extensive areas of riparian forest
have been lost to agricultural and
urban development.
• Typically only a narrow band of
forest remains along larger rivers
where pre-settlement riparian
forests were much wider.
• Most of today's surviving stands of
riparian forest are second-growth
and have been degraded by a variety
of non-native species such as reed
canarygrass and Himalaya
blackberry.
Wet Prairie
• Represented approximately 10% of mid1800’s WV vegetation (roughly onethird of “prairie” in Valley was wet
prairie).
• Heavy clay soils on valley floor that
were perennially saturated or
seasonally flooded
• Typically dominated by tufted hairgrass,
rushes and sedges (Carex spp.).
• TNC estimates that less than 2,024 ha of
wet prairie, remain in the Willamette
Valley today—less than 2 percent of the
former extent of these ecosystems.
Emergent Wetlands
• Covered 3,650 ha, or just under 0.3% of
the mid-1800’s WV vegetation
– Under-estimated since GLO land
surveyors did not typically note theseMost were simply recorded as "marsh"
or "swamp."
• “Swamps” were typically associated
with smaller streams, and many
contained beaver dams.
• Nearly all larger historical emergent
wetlands have been drained and
converted for agricultural use.
Source for all data: “Historical Vegetation of the Willamette Valley, Oregon in the mid-1800’s”
by John A. Christy, Oregon Biodiversity Information Center, and Edward R. Alverson, The
Nature Conservancy (2010).
Riparian Wildlife Habitat
• Most wildlife is not restricted entirely to stream
riparian areas, but several use stream riparian
areas predominantly.
• Focal species include:
American dipper, bald
eagle, American
merganser, harlequin
duck, red-eyed vireo,
willow flycatcher,
American beaver, river
otter, coastal tailed frog
Yellow-billed Cuckoo: Extirpated from
WV due to loss of mature riparian forest
Photo Credit: Ronnie Maum, USFWS
Role of Riparian Habitats in Ecological Function
• Act as vegetative filters, screening
out sediment and other pollutants
from nearby runoff.
• Vegetation controls stream
temperature and contributes
organic matter/ wood used by
aquatic organisms for food and
shelter.
• Link land and water habitats and
have a high level of biodiversity,
providing the interface between
aquatic and terrestrial species.
In Channel Abundance of Wood
Source: “Patterns and Controls on Historical
Channel Change in the Willamette River” (2007)
http://photos.salemhistory.net/cdm4/item_viewer.php?CISOROOT=/specialcol&CISOPTR=881&CISOBOX=1&REC=3
• In 1868, the Corps began removing downed trees (snags) from the Willamette
(Sedell and Froggatt, 1984). Yearly snagging records show that about 1000
downed and streamside trees were removed annually from the mainstem
Willamette between 1868 and 1935.
• In 1875, the Corps suggested continued annual removal of snags and reported
that “not until the dense growth of timber disappears from the banks…can real
and permanent good be accomplished” for navigation.
In Channel Abundance of Wood
• Numerous downed trees helped to create and maintain shoals,
multiple channels, oxbow lakes, and complex aquatic habitats at
the outside bends of the river.
• Snagging in combination with the widespread conversion of
floodplain forests to agriculture (which diminished recruitment of
large wood) and dam construction (which limited the transport of
wood from tributary channels to the main-stem Willamette)
greatly reduced the in-channel abundance of wood.
• With both wood supply and flood peaks reduced, the Willamette’s
channel was far less prone to avulsions (and other ecological
variability) due to wood clogging of channels.
Source: “Upper Willamette River Landscape: A Historical Perspective” by Benner and Sedell (1997)
Trends and Strategies
• Improved Riparian
Mapping
• Synthesis: Unified Vision/
Focusing Resources
• Land Acquisition,
Restoration and
Management of
Non-Native Species
• Integrating Flow and
Restoration
Willamette Valley Riparian Mapping
Streams &
rivers
modeled
using new
technique
for LiDAR
data,
which
works well
even in
urbanized
low relief
areas
Willamette Valley Riparian Mapping
Closeup
area for
landcover
example
High
Low
Height
class--LiDAR
highest hit
above
ground
elevation,
shown
with NAIP
infrared
band
0 -0.5 '
0.5 -3 '
3 -6 '
6 -30 '
30 -80 '
80 -120 '
120 ' +
LiDAR coverage
within study area.
Floodplains can be
delineated without
LiDAR data, but
vegetation height is
impossible.
Willamette Valley Riparian Mapping
Land Acquisition,
Restoration &
Invasives
Integrating flow and Restoration
Willamette River
Environmental Flow
Recommendations
Phase 1: Middle Fork and
Coast Forks of Willamette
• Environmental Flows
• Willamette Floodplain
Restoration Study
Phase 2: McKenzie River
• Environmental Flows