Riparian Landforms and Riparian Landforms and Channel MorphologyChannel Morphology

Organizing the ChaoticOrganizing the Chaotic

N. Phil PetersonN. Phil Peterson

Forest & Channel Metrics, Inc.Forest & Channel Metrics, Inc.

Changing the Way We Think About Changing the Way We Think About Riparian SystemsRiparian Systems

StopStop Focusing OnFocusing OnFishFishRegulatory stream typesRegulatory stream typesTHE ordinary high water THE ordinary high water markmarkSet distancesSet distancesOne size fits all One size fits all prescriptionsprescriptions

Start Focusing OnStart Focusing OnBedrock and surficial Bedrock and surficial geologygeologyTopographic slope breaksTopographic slope breaksLandforms, their origins Landforms, their origins and processesand processesSurfaces and their soilsSurfaces and their soilsUnderstory plant Understory plant communitiescommunitiesProcess based channel Process based channel typestypes

Organizing the ChaoticGeologyGeology–– Bedrock and surficialBedrock and surficial–– Lithotopo unitsLithotopo units

Valley segments (xValley segments (x--sections)sections)–– Riparian landforms (topographic slope breaks)Riparian landforms (topographic slope breaks)

Valley floorsValley floorsValley wallsValley walls

Channel networkChannel network–– Patterns of segment linkagePatterns of segment linkage

Process based channel typesProcess based channel types–– SizeSize–– ConfinementConfinement–– Bed morphologyBed morphology

Benefits of process and ecologically based systemBenefits of process and ecologically based system–– Aquatic assemblagesAquatic assemblages–– DisturbancesDisturbances–– Natural plant potentialNatural plant potential

Lithotopo Units

Terrain units with fundamental differences in Terrain units with fundamental differences in watershed processes and inputswatershed processes and inputs

Valuable scale for integrating important Valuable scale for integrating important information and explaining significant variationinformation and explaining significant variation

For example:For example:–– Crescent UplandsCrescent Uplands–– Recessional Outwash PlainRecessional Outwash Plain–– Sedimentary Inner GorgesSedimentary Inner Gorges

Crescent Uplands

Recessional Outwash Plain

Sedimentary Inner Gorges

Valley SegmentsValley cross sectionValley cross section

Riparian landformsRiparian landforms

–– Valley floors (channel migration and channel disturbance zones)Valley floors (channel migration and channel disturbance zones)FloodplainFloodplainLow terraceLow terraceHigh terraceHigh terraceAlluvial fansAlluvial fans

–– Valley wallsValley wallsUniform slopeUniform slopeCanyonCanyonInnerInner--gorgegorgeBreak in slopeBreak in slopeReverse break in slopeReverse break in slope

Channel Migration Zone

Channel Disturbance Zone

Alluvial Fans

Riparian Landforms Based on Valley Cross Section

Uniform slopeUniform slope

Riparian Landforms Based on Valley Cross Section

CanyonCanyon

Riparian Landforms Based on Valley Cross Section

Inner gorgeInner gorge

Riparian Landforms Based on Valley Cross Section

Break in slopeBreak in slope

Riparian Landforms Based on Valley Cross Section

Reverse break in slopeReverse break in slope

Channel Networks

DendriticDendriticLong unbranchedLong unbranchedTrellisTrellisShort lateralsShort laterals

Systematic patterns of segment linkages Systematic patterns of segment linkages vary by geology vary by geology (River Continuum Concept and (River Continuum Concept and Process Domain Concept diverge)Process Domain Concept diverge)

Dendritic Channel NetworkDendritic Channel Network

Process Based Channel Types

SizeSizeConfinementConfinementBed morphology Bed morphology (Montgomery and Buffington 1997)(Montgomery and Buffington 1997)

–– CascadeCascade–– Step poolStep pool–– Plane bedPlane bed–– Pool rifflePool riffle

CascadeCascade

Step PoolStep Pool

Pool RifflePool Riffle

Benefits of Process and Ecologically Based System

Significant amount of information embedded Significant amount of information embedded in the classificationin the classification

–– Predicts aquatic assemblagePredicts aquatic assemblage–– Identifies likely disturbance regimeIdentifies likely disturbance regime–– Identifies general temperature regimeIdentifies general temperature regime–– Associates natural plant potential with the siteAssociates natural plant potential with the site

Crescent basaltSmallHighly confinedCascade / bedrock

Olympic Torrent Salamander(Rhyacotriton olympicus)

60C

hann

el s

lope

(%)

Basin area (ha)0

10

20

30

40

50

0 25 50 75 100 125 150 1750.00.10.20.30.40.50.60.70.80.91.0

Probability occupied

Temperature Regimes

Channel pattern

Riparian forest shade

Topographic shade and elevation

Groundwater0

0.2

0.4

0.6

0.8

1

8 12 16 20 24

Temperature

Tim

e ex

ceed

ance

Canyon R.Glenn Ck.Bell Ck.Gosnell Ck.Schafer Ck.North Mt. Ck.Save Ck. trib.Bingham Ck.Devils Club Ck.

Plant Associations

UplandsUplandsValley wallValley wallValley floorValley floorActive channelActive channel

TSHE / POMU / TITR

TSHE / OPHO / ATFI

Active Channel

TSHE / GASH / POMU

Hypotheses for Riparian Successional Pathways(Devils Club/Lady Fern Complex)

Red alder Devils club Lady fern

Devils club Lady fern

Western hemlockDevils clubLady fern

Alder senescenceAlder senescenceMass wastingMass wastingFireFireFloodFloodChanges in surface roughnessChanges in surface roughness

Large Wood in Small SteamsLarge Wood in Small Steams

SummarySummaryGeology exerts a strong influence on valley segment Geology exerts a strong influence on valley segment morphology and channel typemorphology and channel type

Valley segment linkages transmit energy and materials Valley segment linkages transmit energy and materials downstream in predictable ways and create legacy downstream in predictable ways and create legacy conditions that influence riparian forestsconditions that influence riparian forests

Key associations exist between valley segment Key associations exist between valley segment morphology and natural plant potential, often characterized morphology and natural plant potential, often characterized by sharp boundaries at slope breaksby sharp boundaries at slope breaks

Integrating this kind of information provides a basis for Integrating this kind of information provides a basis for riparian management decisions and restorative strategies riparian management decisions and restorative strategies