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Fluvial Geomorphic Conditions Critical to Design Treatment
Transcript of Fluvial Geomorphic Conditions Critical to Design Treatment
Fluvial Geomorphic Conditions Critical to Fluvial Geomorphic Conditions Critical to Design TreatmentDesign Treatment
bybyW. Barry Southerland, PhDW. Barry Southerland, PhDFluvial GeomorphologistFluvial Geomorphologist
USDA USDA -- NRCS NRCS -- WNTSC WNTSC –– Portland, OR Portland, OR –– May 4May 4thth -- 20062006
Bank Height Ratio
W.B. Southerland, 2003
W.B. Southerland, 2003
W.B. Southerland, 2003
Rationale for discussionRationale for discussion• To identify and understand the reference-
reach role in approaches to stream restoration practices
• To identify and quantify floodplain attachment measurements critical to vegetative conditions and establishment potential
• Summarize key geomorphic characterizations essential to restoration
“Natural stream channel stability is achieved by “Natural stream channel stability is achieved by allowing the river to develop a stable dimension, allowing the river to develop a stable dimension,
pattern, and profile such that, over time, the stream pattern, and profile such that, over time, the stream system neither aggrades or degrades (incision). system neither aggrades or degrades (incision). For For
a stream to be stable it must be able to consistently a stream to be stable it must be able to consistently transport its sediment load, both is size and type, transport its sediment load, both is size and type,
associated with local deposition and scour.”associated with local deposition and scour.”
Entiat Reference Reach
Width Depth Ratio = 20
Entiat Immediately Upstream
Width Depth Ratio = 48
West Side ReferenceWest Side Reference Big QuilceneBig Quilcene
Geomorphic Reference Site Downstream
Chum Salmon Spawners
• In the cause and effect relationships of streams and riparian communities, it is not a question of “the chicken or the egg” as to which came first. Riparian areas in stream corridors are present by virtue of the floodplain that exists.
Geomorphic meander reGeomorphic meander re--establishment should not be establishment should not be about cultural bias towards a single thread channel it about cultural bias towards a single thread channel it needs to be about channel evolution and the current needs to be about channel evolution and the current
stable analog and targeting a range of natural variability.stable analog and targeting a range of natural variability.
C MorphologyMississippi near Grand Forks - 1994
When you live in the floodplain and the flood comes and you have damages, don’t take it to Judge Wapner – Su the flood!
Floodplain AbandonmentFloodplain Abandonment
Stage I Stage I
Stage II
Schumm Channel Evolution Model and Bank Height Ratio (BHR)
BHR = Top of the Bank / Bankfull Height. This is a measure of the degree of incision
WBS, 2002
WBS, 2002WBS, 2002
Root MatrixRoot Matrix
Rooting Depth
Root Depth = 2.5
Root Matrix = Rooting Depth/Bank Height
To the toe!
WBS - 2003
Root DensityRoot Density
WBS, 2003
Percent of bank that is made up of rootse.g. 30%
e.g. 70% for reference condition
Streambank StratigraphyStreambank Stratigraphy
Gravel & Sand
Sandy Loam
Willow Creek, COPhoto by WBS, 6/2005
Photo by WBS, 1998 Little Klickitat, WA
Factors to address in streambank erosion planning and designFactors to address in streambank erosion planning and design
Wildland Hydrology, 1996
Streambank slope relative to structureStreambank slope relative to structure
Photo by WBS, Ohio Creek, CO, 6/2005
Key geomorphic factors critical to Key geomorphic factors critical to the design the design (not all inclusive)(not all inclusive)
• Bedload transport, competence and capacity
• Stream Slope, Sinuosity, and Profile• Bankfull dimension (width, depth, and
thalweg)• Streambank characteristics (BHR, Strat.
etc.• Valley geomorphology (I-XI), M&B, stream
planform relative to valley geomorphology and historical adjustments.
Geomorphic Valley TypesGeomorphic Valley Types
Wildland Hydrology, 1996
Wildland Hydrology, 1996
Wildland Hydrology, 1996
Wildland Hydrology, 1996
Youthful
Early Mature
Old Age
Old Age
What do William Morris Davis (1899) and Dave Rosgen have in common?
Eight physical factors governing Eight physical factors governing streams and are essential to designstreams and are essential to design
1. Width – at channel forming flow (bankfull)2. Depth – at channel forming flow (bankfull)3. Slope – water surface, bed, sinuosity, valley, slope of the
profile facet (riffle, run, glide, pool)4. Velocity – at bankfull and targeted stages5. Roughness – bed, wood, and streambank materials (veg. and strat.)
6. Discharge – at bankfull and what factors have affected channel formative flow
7. Sediment Size (Competence) What is the stream capable of moving at BFQ?
8. Sediment Concentration (Capacity) What loads can a stream accommodate?
A change in one of these variables sets up mutual adjustments in others
What it is all about.What it is all about.
“Nearly all physical landscapes merge into rivers and oceans. Streams represent a unique natural intensity and complexity on the landscape”
“What’s good for the stream is what’s good for the fish, what’s good for the fish, is what’s good for the kids.”
“Protect the best, restore the rest”