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

Bank Height RatioBank Height Ratio

WENAS Creek near Yakima, WA

Photo by W. Barry Southerland, 1998

Bank Height RatioBank Height Ratio

Photo by WBS, Wenas Creek, WA, 1998

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”