ENSC 202 2004

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Watershed Assessment (ENSC 202)

• Phase 1 Steps 2-5
• Extracted from Vermont ANR Stream Geomorphic
  Assessment Protocols Handbook - Introduction

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Step 2 Determining Stream Types

• 2.1 Downstream and Upstream Elevations
• 2.2 Valley Length
• 2.3 Valley Slope
• 2.4 Channel Length
• 2.5 Channel Slope
• 2.6 Sinuosity
• 2.7 Watershed Size
• 2.8 Channel Width
• 2.9 Valley Width
• 2.10 Confinement
• 2.11 Stream Type

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Notes on Step 2

• This is a first cut only, dont sweat it.
• Focus is on what the reach might be like in the
  absence of human influences a true reference.
• Be consistent in how you make each measurement.
• Be consistent with your measurement units.
• Potential measuring tools ruler, map wheel, GPS
  mapping tools, GIS

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• Step 2.1 Downstream Upstream elevations
• Point at which contour crosses stream
• Interpolate between contours
• Step 2.2 Valley length
• Straight line distance between reach breaks
• Follow tendency (valley walls) not meanders
• Step 2.3 Valley slope
• (change in elevation/valley length)100
• Step 2.4 Channel length
• Actual channel (thalweg) distance
• Note difference from Valley Length (2.2)
• Step 2.5 Channel slope
• (change in elevation/channel length)100
• Step 2.6 Sinuosity
• Channel length/valley length

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• Step 2.7 Watershed size
• Drainage area above downstream reach break for
  each reach
• GIS, planimeter, or graph paper methods
• Step 2.8 Reference channel width (provisional)
• Based on regional hydrologic geometry
• Limitations mid-to-large sized streams in
  unconfined, moderate-to-gentle gradient, alluvial
  settings
• Make best guesses now, you can adjust this later
  with field data from confirmed reference
  reaches
• Step 2.9 Valley width
• Measure width between the first lateral contours
  next to the stream (hard in confined valleys)
• Make 10 measurements per reach/valley and
  average

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Vermont RegionalGeometry Curves
95 confidence intervals
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• Step 2.10 Confinement (provisional)
• (valley width/channel width) 2.9/2.8

• Step 2.11 Reference stream type (Appendix I)
• Based on Rosgen (1996) and Montgomery
  Buffington (1997)

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Step 3 Basin Characteristics Geology and Soils

• 3.1 Alluvial Fan
• 3.2 Grade Controls
• 3.3 Geologic Materials
• 3.4 Valley Side Slopes
• 3.5 Soil Characteristics

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• Step 3.1 Alluvial Fans (Y/N)

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• Step 3.2 Grade controls

• Step 3.3 Geologic materials

NRCS Top 20 soils (?)
Defining channel corridor (Appendix E)
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• Step 3.4 Valley side slope
• Directly from topo maps
• Step 3.5 Soil characteristics
• Hydrologic Group
• Flooding
• Water Table
• Erodibility

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Step 4 Land Cover and Reach Hydrology

• 4.1 Watershed Land Cover / Land Use
• 4.2 Corridor Land Cover / Land Use
• 4.3 Riparian Buffer Width
• 4.4 Groundwater and Small Tributary Inputs

General characterizations based on observations
of older and more current maps, orthophotographs,
existing data, or windshield surveys.
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• Step 4.1 Watershed Land Cover and Land Use
• Current best available
• Historic 1970s orthophotos
• Assign impact rating

• Step 4.2 Corridor Land Cover and Land Use
• Current best available
• Historic 1970s orthophotos
• Assign impact rating

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• Step 4.3 Riparian buffer widths
• left vs right bank
• Record dominant buffer width by bank
• Note particular restoration opportunities

• Step 4.4 Groundwater small tributray inputs
  (wetlands)
• No impact rating?

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Step 5 In-stream Channel Modifications

• 5.1 Flow Regulations and Water Withdrawals
• 5.2 Bridges Culverts
• 5.3 Bank Armoring or Revetments
• 5.4 Channel Modifications
• 5.5 Dredging and Gravel Mining History

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• Step 5.1 Flow regulation and water withdrawals
• Consult with DEC, town records, utilities

• Step 5.2 Bridges and culverts
• Count number
• Will probably have to be augmented with
  windshield surveys

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• Step 5.3 Bank armoring and revetments
• Will probably have to be augmented with
  windshield surveys
• armoring (RB armor length LB armor length
  overlap)
• (total RBRL length)

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• Step 5.4 Channel modifications
• Will probably have to be augmented with
  windshield surveys

• Step 5.5 Dredging and gravel mining history
• DEC Stream Alteration Engineers, town records,
  road commissioners
• Will probably have to be augmented with
  windshield surveys