Stream Assessment Techniques
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Transcript of Stream Assessment Techniques
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Stream Assessment Stream Assessment TechniquesTechniques
March 2013March 2013
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What is Stream Restoration?What is Stream Restoration?
““Reestablishment of the Reestablishment of the structurestructure and and functionfunction of ecosystems” of ecosystems” as closely as as closely as possiblepossible to pre-disturbance to pre-disturbance conditions – (NRC, 1992)conditions – (NRC, 1992)
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Stable StreamStable Stream
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Unstable StreamUnstable Stream
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Goals of Stream Restoration Goals of Stream Restoration ProjectsProjects
Enhance Enhance functionsfunctions of natural systems of natural systems
• Physical Physical
• ChemicalChemical
• BiologicalBiological
• SocietalSocietal
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Areas of ConsiderationAreas of Consideration
• FlowFlow– Magnitude, timing, frequency, durationMagnitude, timing, frequency, duration
• SedimentSediment– Flux, particle shape, size distribution, timingFlux, particle shape, size distribution, timing
• Chemical and thermal Chemical and thermal • GeomorphologyGeomorphology
– Stream types, channel slope, bed and bank Stream types, channel slope, bed and bank materialsmaterials
• LandscapeLandscape– Geology, vegetation, land useGeology, vegetation, land use
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Pools and RifflesPools and Riffles
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Controlling Factors in Stream Controlling Factors in Stream StabilityStability
1.1. WidthWidth
2.2. DepthDepth
3.3. SlopeSlope
4.4. VelocityVelocity
5.5. DischargeDischarge
6.6. Size of sedimentSize of sediment
7.7. Concentration of sedimentConcentration of sediment
8.8. Roughness of channelRoughness of channel
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Discharge CalculationDischarge Calculation
Q = VA
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Sketch MapSketch Map
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Dimension: Cross SectionsDimension: Cross Sections
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Dimension: Cross SectionDimension: Cross Section
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Bankfull IndicatorsBankfull Indicators
• Top of streambankTop of streambank
• Break in slopeBreak in slope
• Top of point barTop of point bar
• Presence of finesPresence of fines
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Bankfull
Top of bank
Left Bank Right Bank
Thalweg
Riffle DimensionsRiffle Dimensions
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Riffle DimensionsRiffle Dimensions
Bankfull
Wbkf
Dbkf
Abkf
W/D = Wbkf / DbkfR = A / WP = Abkf / WPbkf
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Entrenchment RatioEntrenchment Ratio
Bankfull
Wbkf
Dmax
ER = Wfpa / Wbkf
Wfpa
2 x Dmax
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Channel PatternChannel Pattern
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Sinuosity of ChannelSinuosity of Channel
6.5 m
5 m
Sinuousity = Length of ChannelLength of Valley
6.5m5.0m= = 1.3
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Longitudinal ProfileLongitudinal Profile
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Bed MaterialBed Material
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ResistanceResistance
• Roughness is a factor in determining Roughness is a factor in determining depth and velocity of flowdepth and velocity of flow– Decrease in velocity results in increase Decrease in velocity results in increase
in depth given constant dischargein depth given constant discharge
• Important factorsImportant factors– Particle sizesParticle sizes– VegetationVegetation– Other obstructionsOther obstructions
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Physical CharacteristicsPhysical Characteristics
• SedimentSediment– Fines can impact fish and Fines can impact fish and
macroinverebrate habitsmacroinverebrate habits
• Water temperatureWater temperature– Impacts dissolved oxygenImpacts dissolved oxygen– Governs biological processes in some Governs biological processes in some
speciesspecies
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Chemical ConstituentsChemical Constituents
• pHpH
• Dissolved oxygenDissolved oxygen
• NutrientsNutrients
• Toxic organic chemicalsToxic organic chemicals
• MetalsMetals
• SalinitySalinity
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Stream Assessment Stream Assessment TechniquesTechniques• Reach Wide Pebble CountReach Wide Pebble Count• Velocity MeasurementVelocity Measurement• Temperature MeasurementTemperature Measurement• Color/Appearance ObservationColor/Appearance Observation• SurveyingSurveying
– Riffle Cross-sectionRiffle Cross-section– Pool Cross-sectionPool Cross-section– Longitudinal sectionLongitudinal section
• Plant/Animal Identification*Plant/Animal Identification*