step 1: assess riparian resource function using pfc §1d. complete pfc assessment l 17 questions...
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Step 1: Assess Riparian Resource Function Using PFC
1d. Complete PFC assessment 17 questions about attributes and processes Reminder – PFC based on:
• Water (hydrology), • Vegetation, and • Soil & landform (erosion/deposition)
Checklist answers: Yes, No, or N/A (sometimes) Not “Liner” Notes for “No’s”, Many (all?) “Yes’s”, e g. species list
Item #1: Floodplain inundation
FloodplainLevel area near a stream channelConstructed by the streamIn the present climateFlooded during moderate & high flow eventsShould not be confused with terraces (abandoned floodplains)
(adapted from Leopold 1994)
Abandoned floodplain or terrace
Floodplain Channel
Hill slope
Valley flat
Floodplain – Geologic feature being formed by the river in its present condition and climate
Bankfull Concept InformationForest Service Stream Systems
Technology Center (Stream Team) website for on-line training videos, can order CDs and DVDs:
www.stream.fs.fed.us
1.Western U.S.
2.Northeastern U.S. (4 CDs)
3.Forested Streams Eastern U.S.
http://www.stream.fs.fed.us/publications/bankfull_west.html
Bankfull Indicators (Moody et al. 2003, Odem and Moody 1999)
Build a case based on physical evidence Series of depositional features at consistent
elevations with similar substrate and veg components Point bars at inside of meander bends, Point bars often not well developed with low sinuosity, Discontinuous alternating longitudinal bars parallel to
the channel often most dependable indicator Broad valley floors are almost always above bankfull
Field Observations
Floods Terrace
Bankfull
One year flow
Item 1: Floodplain inundated frequently1) Floodplain inundated in “relatively frequent
events” (1-3 years) Purpose: To determine whether frequent flood flows are
capable of spreading out on low-lying areas adjacent to the stream and thus provide for:
• energy dissipation• sediment deposition• periodic flooding of vegetation, and • periodic infiltration of flood water to replenish base flows
Bankfull
Floodplain
Item 1: Floodplain inundated frequently1) Floodplain inundated in “relatively frequent
events” (1-3 years) Flat, depositional surface adjacent to channel
• Low gradient, meandering (“C” and “E” channels)• Moderate gradient “B” channels
Indicators• Channel incision• Vertical banks on inside of bend & at straight reaches• Upland vegetation on streambank
Bankfull
Floodplain
BankfullBankfull
Floodplain
Terrace
Item 2: Beaver dams are stablePurpose: Beaver dams are hydrologic modifiers. Stable dams can increase stability by attenuating flood flows, providing a source for base flows, storing sediment, raising water tables and expanding riparian areas.
Unstable dams can reduce stability by causing channel incision, increasing bank erosion, lowering water tables and decreasing the extent of the riparian zone when they fail.
Indicators of beaver activity• Fresh workings on dams• Available building materials and food supply
Indicators of dams at risk• Single dams• No signs of maintenance and repair• Confined valleys - no floodplain• Large, flashy streams
Item 2: Beaver dams are stable
2: Beaver dams are stable
Examples of visual indicators Dam construction material Dams keyed into streambanks Breaches
Yes No NA
Item 3: Dimension, Pattern and Profile
3) Sinuosity, gradient, and width/depth ratio, are in balance with the landscape setting (i.e., landform, geology, and bioclimatic region)
Purpose: To determine if the pattern, dimension, and profile of the stream are within the expected range, given its landscape position, hydrologic regime, and natural sediment load.
Sinuosity, width/depth ratio, and gradient perform key roles in determining whether a stream can transmit water and sediment while managing erosive forces and remaining stable
Item 3: Dimension, Pattern and Profile
3) Sinuosity, gradient, and width/depth ratio, are in balance with the landscape setting (i.e., landform, geology, and bioclimatic region) Question has three parts
• Sinuosity• Width/Depth ratio• Gradient
All three must be "yes" for answer to be "yes" Must be appropriate for site
Sinuosity = Stream Length ÷ Valley Length1.9 = 370' ÷ 195'
Valley Gradient = 1.5%Stream Gradient = 0.8%
3) Sinuosity, gradient, and width/depth ratio, are in balance with the landscape setting (i.e., landform, geology, and bioclimatic region)
Examples of visual indicators Aerial photos
help with sinuosity
3.) Sinuosity, gradient, and width/depth ratio, are in balance with the landscape setting (i.e., landform, geology, and bioclimatic region)
4.) Riparian zone is expanding or has achieved potential extent.
Purpose: To document that a riparian area is recovering or has recovered.
Examples of visual indicators Riparian-wetland
community types expanded to valley edge
Stream narrowed Upland plants dying or
dead Depositions being
captured
4) Riparian area is expanding or has achieved potential extent
Yes No NA
Item 5: Riparian impairment from the upstream or upland watershed is absent.
5: Riparian impairment from the upstream or upland watershed is absent.
Trapping Cr BC 1996 Belgo Cr BC 1996
Yes No NAYes No NA
Degradation related to upstream or upland factors
Is there riparian degradation?
No riparian degradation observed.
Item 5 = “Yes”
Yes, riparian degradation observed
Degradation related to in situ activities
Item 5 = “Yes”
Item 5 = “No”
Yes
No
Purpose: To determine if riparian degradation is caused by a management within the riparian area or by environmental conditions or management outside the riparian area.