Physical Assessment of Streams: Rosgen Classification of Natural Rivers and WARSSS

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Physical Assessment of Streams Rosgen
Classification of Natural Rivers and WARSSS
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Rosgen Classification of Natural Rivers
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Rosgen
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Rosgen
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Rosgen Stream Stability Analysis
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Departure from Existing Condition
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Rosgen, fgmorph
Field Assessment of Erosion Potential (BEHI)
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Williams Creek, Fall 2007
J. Webber
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Channel Adjustment Tendency
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Channel Evolution and Departure
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Channel Evolution and Return
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Watershed Assessment of River Stability
Sediment Supply (WARSSS)
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Why WARSSS?

• The U.S. Environmental Protection Agency
  supported the development of WARSSS by Dr. David
  L. Rosgen because there is limited guidance on
  assessing sediment impairments.
• WARSSS can be used to analyze known or suspected
  sediment problems, develop sediment remediation
  and management components of watershed plans,
  develop sediment TMDLs (Total Maximum Daily
  Loads), and other uses.
• This web-based assessment tool was designed for
  scientists who need to assess sediment-impaired
  waters in planning for their restoration.

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USEPA
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USEPA
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USEPA
Reconnaissance Level Assessment
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Reconnaissance Level Assessment (RLA)

• Identify places in the watershed that represent
  likely sediment sources and channel stability
  problems, and thereby limit the effort and costs
  of the more intensive WARSSS phases
• Begin assembling and examining existing
  information
• Verify or, if needed, clarify or redirect the
  problem identification
• Eliminate sub-watersheds, reaches or areas within
  the watershed (e.g., stable slopes) that do not
  contribute excessive sediment
• Locate and focus on potentially important problem
  areas, reaches, or sub-watersheds for the next
  phase, RRISSC level assessment

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Rapid Resource Inventory for Sediment Stability
Consequence (RRISSC)
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Rapid Resource Inventory for Sediment Stability
Consequence (RRISSC)

• Sensitive landscapes, potentially unstable stream
  systems, and sediment-generating land use
  activities need to be identified, prioritized,
  and assessed for potential impacts at a level of
  detail beyond their initial flagging in RLA.
• The Rapid Resource Inventory for
  Stability/Sediment Consequence (RRISSC) is
  designed to provide this finer level of analysis.
  
• Time required to assess a 3rd order watershed
  using the RRISSC is measured in a few weeks
  (rather than days or months), depending on
  availability of land cover maps, aerial
  photographs, soils information, and access to
  land use history.

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Rapid Resource Inventory for Sediment
Stability Consequence (RRISSC)

• type and extent of land uses
• the erosion potential of the landscape and
  channel
• relationship of potential sediment sources to
  hillslope, hydrologic and channel processes

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USEPA
Prediction Level Assessment (PLA)
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Prediction Level Assessment (PLA)

• The most detailed level of investigation for
  slopes, sub-watersheds and river reaches
  previously identified as being high risk
  associated with sediment and/or river stability
  problems.
• Due their sensitive nature, the value of the
  resource, the severity of the adverse consequence
  of impairment, and other compelling reasons, it
  becomes necessary to conduct this level of
  analysis.

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Prediction Level Assessment (PLA)

• Utilizes "reference condition" that represents
  stable natural land and/or stream systems to
  compare direction, rate, nature and extent of
  departure from natural rates of sediment and/or
  natural stability using the same assessment
  methodology.
• These comparisons to reference sediment and
  stability condition are used to identify
  potential departure, and to document acceptable
  erosional/sedimentation rates.

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The Reference Reach

• The reference reach is a river segment that
  represents a stable channel within a particular
  valley morphology.
• The reference reach is used to develop natural
  channel design criteria based upon measured
  morphological relations associated with the
  bankfull stage for a specific stable stream type.
  
• Specific data on stream channel dimension,
  pattern, and profile are collected and presented
  by dimensionless ratios by stream type.
• The morphological data collected are used for
  extrapolation to disturbed, or unstable reaches
  in similar valley types for the purposes of
  restoration, stream enhancement, stabilization,
  and stream naturalization schemes.
• Bankfull discharge and dimensions from stream
  gage stations for a particular hydro-physiographic
  regions are correlated with drainage area to
  develop regional curves for extrapolation to
  non-gaged reaches.

Rosgen
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Williams Creek, Fall 2007