Presented by Rose Wallick of USGS as part of the Science Progress Report at Within Our Reach 2012.

1. Processes and Landforms of the
Willamette River and Floodplain:
Current Understanding and Information
Needs
Rose Wallick Dave Hulse
Jim O’Connor Stan Gregory
Krista Jones
Mackenzie Keith
Charles Cannon
U.S. Department of the Interior
U.S. Geological Survey

2. Introduction
• Previous studies Upper Willamette
documented historical
changes and created Historical Channel Change
rich datasets
• Much is still unknown
about “modern”
channel processes
1850 1995
Map sources: Willamette Planning Atlas; Hulse and others 2001

3. Emerging Management Challenges
for the Willamette Floodplain
What are reasonable targets for restoration strategies?
Revetment
What happens if…
Revetments are modified?
Environmental flows are implemented?
Multiple strategies are implemented?
Photo courtesy of Freshwaters Illustrated

4. Geomorphic Processes Shaping
Willamette Valley Floodplains

5. Purpose and Approach
Overarching goal:
Build a roadmap towards better understanding of
geomorphic processes in Willamette Valley
Study Approach:
 Describe floodplain landforms and processes
 Explain our current understanding
 Identify major knowledge gaps
 Outline future studies

6. Study Area
Willamette Geomorphic
Floodplain
 Alluvial, gravel-bed portion
of Willamette River and
major tributaries
 Landforms and geomorphic
processes broadly similar
 Interconnected system of
landscapes and ecosystems

7. Comparison of Landforms along
Willamette River
High Channel Complexity Low Channel Complexity
Stable,
vegetated bar
Side
Gravel channel
bars
Side
channels
Upper Willamette Middle Willamette
upstream of Harrisburg near Albany
Aerial photographs from 2011

8. Comparison of Landforms along
Tributaries
High Channel Complexity Low Channel Complexity
Side
channels
Stable,
vegetated bars
Active Side
bars channels
Lower North Santiam Middle Fork
near Wiseman Island near Jasper State Park
Aerial photographs from 2011

9. Diversity of Channel Morphologies Reflects
Differences in Geomorphic Processes
Key
geomorphic
processes

10. Geomorphic Processes: Flooding
Flooding drives channel change
Creates and maintains riparian habitats
Key questions:
How do different magnitude flows shape landscape?
Are key habitats being created and maintained?
Photo courtesy of Freshwaters Illustrated

11. Geomorphic Processes:
Gravel Transport
Coarse sediment is building block of the
channel and floodplain habitats
Key questions:
Balance between gravel supply and transport?
Future distribution and size of gravel bars?
Photos courtesy of Freshwaters Illustrated

12. Gravel
(preliminary) Estimates supply,
without
of Gravel Transport dams
Geology Estimate
and Slope Gravel
Yield
Abrasion Gravel routed
through stream
network
Final
gravel flux
Many uncertainties and
does not account for bank erosion

13. Gravel
Gravel
(preliminary) Estimates supply,
Supply
including
of Gravel Transport dams
Geology Estimate
and Slope Gravel
Yield ~60%
decrease
in gravel
transport
Abrasion Gravel routed
through stream
network
Trapping by
dams
Final
gravel flux
Many uncertainties and
does not account for bank erosion

14. Gravel Supply vs Transport
Supply: Transport Capacity:
Gravel volume and characteristics Amount of gravel a river can carry

15. Gravel supply vs transport
When supply equals or exceeds transport:
- Larger, more numerous
gravel bars
- More channel shifting
- More complex habitats

16. Gravel Supply vs Transport
When supply equals or exceeds transport:
- Larger, more numerous
gravel bars
- More channel shifting
- More complex habitats
Rivers with ample bed-material sediment
tend to look like the lower North Santiam,
but no comprehensive gravel transport
studies have been conducted for this river
Lower North Santiam

17. Gravel Supply vs Transport
When transport capacity exceeds supply:
- Fewer gravel bars
- More stable channel planform
- Coarsening of channel bed
- Potential for incision
- Fewer, less complex habitats

18. Gravel Supply vs Transport
When transport capacity exceeds supply:
- Fewer gravel bars
- More stable channel planform
- Coarsening of channel bed
- Potential for incision
- Fewer, less complex habitats
Rivers with limited gravel transport tend to
look like the Middle Fork, but no
comprehensive studies of gravel transport
have been conducted for this river
Middle Fork Willamette River

19. Geomorphic Processes:
Floodplain Vegetation Succession
Riparian forests provide habitat for aquatic, riparian and terrestrial
species, enhance water quality and contribute large wood
Key Questions:
Are diverse forest mosaics being created and maintained?
Extent and implications of vegetation encroachment?
Aerial photo of Upper Willamette downstream of Harrisburg;
Photos courtesy of Freshwaters Illustrated

20. Vegetation Succession:
Emerging Issues and Questions
Recent research shows: Bank protection
1) Channel stability limits bar growth
2) Areas of new colonization are
often “reset” by high flows.
3) Existing stands are maturing –
increase in forest within 2 yr
floodplain but losses elsewhere
Flow
direction
Implications for stand diversity?
Willamette near Snag Boat Bend
Sources:
Cline and McAllister, 2012; Hulse and others, unpublished data

21. Key Questions
Regarding channel processes in Willamette floodplain
Numerous questions and issues….
How do different flows Are key habitats being What is the balance
Where is gravel
shape habitats? created and maintained? between gravel supply
coming from?
and transport?
Are forest mosaics being What is the extent and
implications of vegetation How does gravel transport
created and maintained? relate to habitat availability?
encroachment?
Three overarching questions:
1) What habitats and landforms compose modern floodplain?
2) How are geomorphic processes currently shaping these habitats?
3) How do landforms and geomorphic processes relate to vegetation?

22. Future Steps to Address Knowledge Gaps
Comprehensive studies to understand geomorphic processes
shaping modern Willamette Floodplains
1. Create an inventory of habitats and landforms
• Detailed geomorphic mapping of floodplain based on
demonstration study conducted in 2012 (see poster session)
2. Relate landforms with formative processes
• Evaluate gravel supply and transport using multiple approaches
• Assess channel and floodplain evolution with repeat photos and
surveys
3. Assess vegetation succession
• Evaluate relationships between geomorphology, hydrology and
vegetation for broad areas of floodplain
• Comprehensive monitoring and repeat photo analyses

23. Next Steps
Anticipated Publications:
Willamette geomorphic “issues”
study: Summer 2013
Western Oregon gravel transport
and channel morphology:
late 2013 (?)

24. Acknowledgements
Funding:
Benton Soil and Water Conservation District
USGS Cooperative Water Program
Meyer Memorial Trust and Oregon Watershed Enhancement Board
Assistance and insight to Willamette River issues:
Pam Wiley (MMT) Leslie Bach (TNC)
Eric Jones (MMT) Dan Bell (TNC)
Ken Bierly (OWEB)
Jason Knuckles (TNC)
Jenny Ayotte (BSWCD)
Jeremy Monroe (Freshwaters Illustrated) Anne Mullan (NOAA Fisheries)
Pete Klingeman (OSU-retired) Chris Budai (USACE)
Brian Bangs (ODFW) Rick Bastach (City of Portland)
Kirk Schroeder (ODFW) Scott Wright (RDG)
Greg Taylor (USACE) Troy Brandt (RDG)
Steve Smith (USFWS-retired)
Janine Castro (USFWS/NOAA)
Steve Cline (EPA)
Kathryn Boyer (OSU; NRCS-retired) Rob Markel (NOAA Fisheries)
Joe Moll (McKenzie River Trust) Sarah Schanz (Univ. Washington)
Chris Vogel (McKenzie River Trust) Joseph Mangano (Colorado State Univ.)

25. Questions?