Morphology and PerformanceBased Assessment of Stream Restoration

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Morphology and Performance-Based Assessment of
Stream Restoration

Barbara Doll, PE, Extension Specialist NC Sea
Grant and Biological and Agricultural Engineering
Department, NC State University
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Stream Restoration Expenditures

• Nationally gt 1 billion (Bernhardt et al., 2007)
• NC EEP - 1,000,000 feet x ave. cost 260/ft
  260 million (Jeff Jurek, NC EEP)
• NC CWMTF - No current tally, allocate 33
  million annually to restoration projects

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Why Evaluate Stream Restoration Projects?

• Compliance with mitigation rules
• Lack of post-construction monitoring nationwide
• Evaluate ecological recovery
• Evaluate project effectiveness
• Adaptive management
• Optimize future efforts
• Public acceptance
• Secure future funding

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Current NC Mitigation Monitoring Requirements

• Channel Geometry longitudinal profile and
  cross-sections including the floodplain
• Vegetation
• Substrate Pebble Count
• Macroinvertebrate (rarely)

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Riffle
Run
Pool
Glide
Max Pool
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Bed Material (Substrate) Silt/Clay lt 0.062
mm Sand 0.062 2 mm Gravel 2 64 mm Cobble
64 256 mm Boulder 256 2048 mm
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Substrate CharacterizationPebble Count
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Stability Assessment

• http//www.epa.gov/warsss/index.htm

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Vertical StabilityDegradation/Aggradation

• Bank Height Ratio
• Entrenchment Ratio

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Bankfull Discharge

• The flow that fills the active channel and begins
  to spread onto the floodplain
• Represents the break between channel processes
  and floodplain processes
• For a channel in equilibrium, assumed to equal
  the effective discharge

• Bankfull stage is identified in the field
• Return Period typically between 1 and 2 years

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Bankfull Indicators

• Top of streambank
• Break in slope on streambank
• Top of point bar
• Note Pay attention to flat sandy depositional
  surfaces

Bankfull
Bankfull
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Bank Height Ratio
BHR Dmax tob / Dmax
Dmax tob Max Depth from top of low bank to
thalweg
Dmax Max Depth from bankfull stage to thalweg
Bankfull
Dmax tob
Dmax
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BHR 5.3 / 2.5 2.1
Top of Bank
Bankfull
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Entrenchment Ratio
ER Wfpa / Wbkf
Wfpa Width of Flood Prone Area measured at the
elevation twice bankfull max depth above thalweg
Wbkf Width of Bankfull Channel
Wfpa
Bankfull
2 x dmax above thalweg
dmax
Wbkf
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Lateral Stability

• Meander Width Ratio
• Bank Erosion (BEHI)

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Meander Width Ratio
MWR Wblt / Wbkf
Wblt Belt Width
Wbkf Bankfull Width of Riffle Cross-Section
Wbkf
Wblt
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Bank ErosionMonitoring
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Bank Erosion Hazard Index (BEHI)
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Rapid Stream Assessment for NC CWMTF

• Evaluate project status
• Determine if project goals were met
• Identify specific common problems
• Provide recommendations to improve future
  projects

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Stream Rapid Assessment Phase I, Summer 2006

• 18 stream restoration projects selected for review

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Variability in the data

• 5 Ecoregions
• Land Cover 5 urban, 13 rural projects
• Project Age 1-7 years
• Enhancement to full restoration (dimension,
  pattern profile)
• Some projects had repairs

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Mechanics of Stream Evaluation

• Rapid Assessment - approximately 2-3 hours per
  project
• Four teams of two-people
• Physical
• Vegetation
• Bug
• Rover

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Stream Assessment Protocol
B. Bank and Riparian Habitat
D. Condition and Function of Structures
C. Aquatic Insects
A. Channel Condition
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A. Channel Condition Evaluations

• A1- Bedform
• A2 - Substrate
• A3 - Cover and Refuge

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A1. Bedform

• Evaluate location, design and biological function
  of major channel geomorphic units (riffles,
  pools, runs, and structure related habitat) and
  additional channel geomorphic units (CGUs).

• Pocket Water
• Plunge Pools
• Cascades
• Edgewater
• Lateral Scour Pool

• Step Pool
• Rapids
• Bedrock Sheet
• Backwater Pool

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A2. Dominant Substrate Material

• Pebble counts are conducted at two riffles
• -D50
• -D84
• - lt 2mm

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A3. Cover and Refuge

• Cover type (leaf packs, macrophytes, woody
  debris, overhanging vegetation, etc)
• Overall instream cover

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B. Bank and Riparian Habitat Conditions

• B1. Streambank Stability Assessment (Modified
  BEHI)
• B2. Health and Condition of the Riparian
  Vegetation
• B3. Floodplain and Floodplain Soils

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B1. Streambank Stability Assessment

• Streambank stability - modified BEHI (Rosgen)
• Bank Height / Bankfull Height
• Root Depth / Bank Height
• Root Density
• Bank Angle
• Surface Protection
• Near Bank Stress

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B2. Health Condition of the Riparian
Vegetation

• Structural Complexity and Species Diversity
• Planted Trees/Shrubs/Livestakes
• Natural Tree and Shrub Regeneration
• Invasive Exotic Species
• Streambank Root Mass

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B3. Floodplain and Floodplain Soils

• Six floodplain characteristics (7 in urban
  streams)
• Floodplain connection
• Vegetated buffer width
• Floodplain habitat
• Floodplain encroachment
• Soil characteristics and rooting medium
• Percent exposed or bare ground
• Stormwater outfall quality (urban projects only)

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C. Aquatic Insect Community

• Aquatic insects collected upstream and within the
  project
• Abundant taxa in common
• EPT abundance
• Number of indicator taxa
• shredders and predators

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D. Instream Structure Evaluation

• Structure Condition
• Structure Function

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Cross Vane Functions

• Bank protection
• Flow Concentration (pool formation)
• Grade control
• Habitat enhancement

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Rootwads

• Bank Protection
• Habitat

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Results

• Most common project goals are reducing streambank
  erosion and establishing floodplain connection
• Most projects met the intended goals
• Some observed problems
• Poor riparian vegetation
• Aquatic insects are colonizing the new features
  however, complete recovery hasnt yet occurred
• Sedimentation from upstream sources
• Streambank erosion in critical areas
• Some structure failures due to poor construction

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Results Summed scored for all sites
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Riparian Vegetation

• Many projects have healthy growing riparian
  buffers
• Problems related to
• Poor soil conditions
• Mowing
• Invasive exotic plants

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Urban projects have lower riparian vegetation
quality than rural projects
Urban Projects
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Newer projects have slightly higher riparian
vegetation quality than older projects
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Aquatic Insects

• Most streams are developing an aquatic insect
  fauna
• Aquatic fauna potentially inhibited by
• Upstream water quality impacts (e.g. stormwater)
• Excessive sedimentation
• Poor riffle/pool bedform

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Urban projects have lower macroinvertebrate
quality than rural projects
Urban Projects
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Older projects have higher macroinvertebrate
quality than newer projects
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Stream Stability

• Many projects have stable dimension, pattern, and
  profile
• Problems related to
• Structure failure
• Excessive sedimentation
• Streambank erosion

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Channel stability is not related to watershed
land use (rural vs. urban)
Urban Projects
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Channel stability is not correlated with age of
project
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• Successful Structures
• Properly designed and constructed
• Small elevation drop
• Sealed to prevent piping
• Riffles constructed to maintain length

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• Structure Failures
• Rocks or logs not placed properly
• Piping under or through rocks or logs
• Excess scour

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Conclusions

• Most projects are meeting goals of stabilizing
  channels and creating accessible floodplains
• Poor riffle/pool bedform observed at many sites
  due to both design and implementation
  (potentially leading to poor aquatic insect
  populations)
• Ecological recovery (habitat and benthic
  macroinvertebrate communities) may require many
  years
• Recolonization of the riparian area is critical
  for ecological recovery
• Water quality improvement depends on watershed
  factors including stormwater, sedimentation and
  point sources
• Long-term intensive monitoring is necessary to
  evaluate ecological success

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Systematic Performance Index

• Rapid visual assessment of stream physical
  condition (form and function)
• Channel bedform
• Channel pattern
• Floodplain connection
• In-stream habitat features
• Sediment transport
• Streambank Condition
• Streambank vegetation

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Objectives

• Establish the range of morphologic structure and
  function for high quality reference streams
• Determine if stream restoration projects exhibit
  morphologic form and function that is comparable
  to reference streams.
• Determine if watershed, landscape or design
  parameters influence the morphologic form and
  function of streams.

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High-quality reference streams serve as design
templates
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Determine Restoration Potential
Reference Reaches
Restored Streams
Performance Index Range
Disturbed Channels
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NC EEP Reference Reach Study
Map courtesy of Brian Lowther
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• Channel Bedform
• Riffles
• Steps
• Pools

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Consider location and quality of bedform features
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Channel Pattern
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In-Stream Habitat
Bedrock, Boulders or Boulder Clusters
Large Woody Debris
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In-Stream Habitat
Stable Undercut Banks
Fine Roots
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In-Stream Habitat
Leaf Packs
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Sediment Transport
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Streambank Condition
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Streambank Vegetation
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Floodplain Connection
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Preliminary Results
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Is the Performance Index a consistent method for
evaluating the morphological condition of stream
restoration projects?
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What factors best predict the performance of a
stream restoration project?

• Watershed drainage area size, impervious,
  landuse/landcover
• Landscape valley type, valley slope, substrate
  composition
• Restoration design parameters Dimensionless
  Ratios, Sinuosity, Slope, Stream Type

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Watershed Assessment
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Detailed GIS Analysis of Land Use/Land Cover
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Future Work

• Visit 70 additional stream restoration projects
• Visit 16 disturbed/unstable streams
• Collect site and design data from EEP, CWMTF and
  project designers
• GIS analysis of all watersheds
• Statistical analyses to determine which variables
  best relate to the Performance Index scores