StreamWatch Land Use Study 51 sites Selected to cover a range of - - PowerPoint PPT Presentation

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StreamWatch Land Use Study 51 sites Selected to cover a range of - - PowerPoint PPT Presentation

Nov 03, 2022 171 likes •414 views

StreamWatch Land Use Study 51 sites Selected to cover a range of land use/land cover conditions Streams of all sizes and types StreamWatch Land Use Study DATA Biological 2.5 years of bug sampling spring 2007 through

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StreamWatch Land Use Study

  • 51 sites
  • Selected to

cover a range of land use/land cover conditions

  • Streams of all

sizes and types

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SLIDE 2

DATA Biological

  • 2.5 years of bug sampling – spring 2007 through spring 2009
  • Average of 6 bug samples per site
  • Bacteria

Geomorphological

  • Channel dimensions, slope
  • Particle size (Wolman pebble count)

Local Habitat

  • EPA rapid visual
  • Streambed permeability

Watershed Land Use/Land Cover

  • LU/LC classes: impervious, forest, open land, etc.
  • Cattle population density
  • Human population density

StreamWatch Land Use Study

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StreamWatch Land Use Study

BUG DATA

  • Similar to Virginia DEQ’s

Virginia Stream Condition Index

  • Approved for use as

“Level III” data by DEQ

  • 200 organisms per
  • sample. Each organism

ID’d to family

  • For analyses, we looked

at average index scores, average # of families, and assessed health.

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StreamWatch Land Use Study

LAND USE/LAND COVER

  • Impervious
  • Forest (deciduous,

evergreen, plantation)

  • Forest harvest
  • Open land
  • Orchard, vineyard,

golf course, bare soil

  • Cattle population,

grazed pasture

  • Human population
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Watershed class Number of watersheds Approximate %

  • f Rivanna land

area Average population density (per square mile) Average percent forest cover Average percent impervious cover Wild 2 1% 1 97% 0.6% Rural 26 14% 28 80% 1.0% Exurban 113 60% 86 71% 2.0% Suburban 39 21% 367 65% 5.6% Urban 9 5% 2,393 49% 25.0% Land use/land cover conditions in 189 small Rivanna subwatersheds classified according to population density.

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Extirpation (local extinction) correlates with land use intensity

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Center for Watershed Protection’s conceptual model

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General relationship between health and IC

biological condition vs % impervious - 1st to 5th-order systems, not including sites near point sources (n=42) R2 = 0.82 10 20 30 40 50 60 70 80 90 0% 10% 20% 30% 40% 50% watershed % impervious average biological index score

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Comparison of SW results with conceptual model

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  • Impervious cover is not the only important

watershed-scale factor.

  • In rural, exurban, and suburban systems, forest

cover correlates with stream health as strongly as impervious cover.

  • IC and FC covary only moderately, therefore

both factors should be considered when assessing risk of degradation in non-urban streams.

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SLIDE 11

biological condition vs % impervious - 1st to 5th-order systems, not including sites near point sources (n=42) R2 = 0.82 10 20 30 40 50 60 70 80 90 0% 10% 20% 30% 40% 50% watershed % impervious average biological index score biological condition vs % impervious - 1st to 5th-order systems, not including sites near point sources (n=42) R2 = 0.82 10 20 30 40 50 60 70 80 90 0% 5% 10% 15% 20% watershed % impervious average biological index score

good fair poor

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Urban (9) Suburban/mixed (11) Exurban/mixed (15) Rural or Wild (7)

Watershed type / number of cases

8.0 7.0 6.0 5.0 4.0 3.0 2.0

Assessed biological condition Virginia aquatic life standard

Very good or good Fair Poor

More than half of exurban streams did not meet the Virginia aquatic life standard.

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SLIDE 13

Rivanna basin – predominately exurban

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Cows

Cattle operations, quantified at the landscape scale, showed no distinctive significant relationship with stream biological condition. The analysis is confounded somewhat by cattle/deforestation

  • covariance. Nevertheless,

cattle effects at the landscape scale seem to be

  • f minor or negligible

importance relative to impervious cover and deforestation.

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Bank erosion and sediment

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Riparian buffer Conditions in the riparian buffer zone correlate moderately with biological condition, and appear to mitigate landscape- scale effects to some extent.

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Watershed stories

Albemarle County reference stream #2

  • 0.7 square miles
  • Class – reference
  • Impervious - 1.0%
  • Forest - 99%
  • People/sq mile - 0
  • Health - very good (76)
  • Sensitive bugs - 12
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Watershed stories

Buck Mountain Creek upper west of Rt 666

  • 20.9 square miles
  • Class - rural/exurban
  • Impervious - 1.2%
  • Forest - 82%
  • People/sq mile – 50
  • Health - very good (72)
  • Sensitive bugs - 9
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StreamWatch Land Use Study

Mechums River trib near Whipporwill Drive

  • 0.5 square miles
  • Class – suburban
  • Impervious - 5.8%
  • Forest - 89%
  • People/sq mile - 340
  • Health - good (66)
  • Sensitive bugs - 9
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Watershed stories

Town Creek @ Dunlora Drive

  • 0.4 square miles
  • Class – urban
  • Impervious - 15.4%
  • Forest - 48%
  • People/sq mile – 1,200
  • Health - fair (52)
  • Sensitive bugs - 6
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Watershed stories

Carroll Creek in Glenmore

  • 5.8 square miles
  • Class - suburban
  • Impervious - 4.2%
  • Forest - 66%
  • People/sq mile - 262
  • Health - poor (39)
  • Sensitive bugs - 3
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Watershed stories

Rivanna trib #2 in Woodbrook

  • 0.5 square miles
  • Class – urban
  • Impervious - 43%
  • Forest - 37%
  • People/sq mile– 1,800
  • Health - very poor (20)
  • Sensitive bugs - 0
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Urban Streams – 1 sensitive bug Suburban Streams – 5 sensitive bugs Exurban Streams – 7 sensitive bugs Rural Streams – 8 sensitive bugs Reference Streams – 11 sensitive bugs