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Identifying Changes to Stream Condition caused by Urbanization. How understanding the responses can improve ecological risk characterization ---------------------------------------- James Coles – USGS Thomas Cuffney – USGS Cornell Rosiu – EPA.

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identifying changes to stream condition caused by urbanization

Identifying Changes to Stream Condition caused by Urbanization

How understanding the responses can improve ecological risk characterization

----------------------------------------

James Coles – USGS

Thomas Cuffney – USGS

Cornell Rosiu – EPA

slide2

National Water-Quality Assessment (NAWQA) Program Urban Stream Studies

Seattle

Portland

BOSTON

Milwaukee

Salt Lake City

Sacramento

Denver

Raleigh

Atlanta

Birmingham

Dallas

Boston = NECB

New England Coastal Basins

setting up the study design
Setting up the Study Design
  • Define homogeneous environmental setting.
    • minimize natural variability
  • Determine watershed indicators of urbanization.
    • related to human presence
  • Select sites to represent urban intensity gradient.
    • minimal to high levels of urbanization
  • Establish consistent sampling reaches
    • 150 meters, riffles, riparian cover, stable channel
slide5

Develop an Index to measure Urban Intensity

Low Urban (0)

High Urban (100)

and which also corresponds to stream condition

slide6

Original (a priori) Index of Urban Intensity (UII) used 24 landuse and demographic variables to characterize an urbanizing landscape.

Infrastructure (Dams, Roadways, TRI sites)

Land cover (Forest, Developed land)

Census statistics(Population, Socioeconomic factors)

slide7
Perhaps an Index of Urban Intensity (UII)could be derived that is as effective,but uses fewer than 24 variables

Revised UII

  • Road Density
    • Expansion of Infrastructure
  • Percentage of Buffer in Forest
    • Encroachment along riparian zone
  • Percentage of Developed land
    • Change from natural landscape
  • Population Density
    • Human presence on landscape
comparing the urban intensity indices uii
Comparing theUrban Intensity Indices (UII)

a prioi UII (24 variables)

revised UII (4 variables)

impervious surface area isa compared to revised and the a priori uii

NOAA ISA

revised - UII

a priori UII

Impervious Surface Area (ISA) compared to Revised and the a priori UII

r2=0.948

r2=0.982

impervious surface area compared to urban intensity revised uii

40

Y= 0.37X + 0.91

R2 = 0.982

30

Percentage ISA

20

10

0

0

20

40

60

80

100

Urban Intensity

Impervious Surface Areacompared to Urban Intensity (revised UII)
response of functional group and taxa tolerance
Response of Functional Group and Taxa Tolerance

Threshold Response

Linear Response

response of water quality to urbanization

4

3

WQ Index (enrichment)

2

1

0

0

20

40

60

80

100

Urban Intensity

Response of Water Quality to Urbanization

Parameters in WQ index:

- TKN

- pH

- Conductance

- Alkalinity

slide15

Improving Ecological Risk AssessmentsThe value of knowing the urban intensity of a site where contamination occurs.(Is it urban intensity or the Superfund-site that is affecting stream condition?)

slide16

Eastland Woolen Mill SiteA Superfund Site in Corinna, ME.

3

Reference

(Lake)

25

Correspondence Analysis, interpretation of the biplot :

The two sets of reference sites are distinct from the group that has the contaminated sites.

27

26

2

CA - Axis 2

1

Reference

(River)

Contaminated

0

22

23

24

-1

-1

0

1

2

3

4

CA - Axis 1

urban intensity used to define the expected condition
Urban Intensity used to define the expected condition

Large dot represents the Nyanza

Superfund site. The Ecological

Condition metric indicates that

the cleanup was successful.

developing applications of the urban intensity index
Developing Applications of the Urban intensity Index

Addressing the details

  • Variables used in an urban index can be somewhat esoteric: Socioeconomic factors
  • The Urban Intensity Index is standardized over the range of study sites, scaled 0 -100.
  • Results from a single study of 30 sites may be tentative. Other data could be used to corroborate the Urban Intensity Index and the ecological responses.
set up the equation to include the landuse variables
Set up the equation to include the Landuse Variables

Urban Intensity = (ROAD*12.5)+(BUFF%*1.74)+(DEV%*1.53)+(POP *8.09))*0.25)

  • ROAD = road density [road length (km) / watershed area (km2)]
  • BUFF% = percentage stream buffer not in forest landcover [MRLC level 1]
  • DEV% = percentage watershed in developed landcover [MRLC level 1]
  • POP = population density, people per hectare [U.S. census data]
urban intensity index modeled vs scaled

120

100

Y = 0.97X + 13.6

80

Urban Intensitymodel

60

40

20

0

0

40

60

80

100

20

Urban intensity (scaled)

Urban Intensity Indexmodeled vs. scaled

Intercept

regressions between response variables and the urban intensity index
Regressions between response variables and the urban intensity index

Response Regression

Variable Coefficient (r2)

_________________________________________________________________________________________________________

EPT Richness (-) 0.743

% Richness non-Insects (+) 0.837

Taxa Tolerance Index (+) 0.824

WQ Index (+) 0.834

__________________________________________________________

expected stream condition based on urban intensity of watershed
Expected stream condition based on Urban Intensity of watershed

6

5

4

Taxa Tolerance

(Expected)

3

2

1

0

0

40

60

80

100

20

Urban intensity

expected stream condition based on urban intensity of watershed1
Expected stream condition based on Urban Intensity of watershed

6

Acme Chemical Site

  • Urban Intensity = 40

5

4

Taxa Tolerance

(Expected)

3

2

1

0

0

40

60

80

100

20

Urban intensity

expected stream condition based on urban intensity of watershed2
Expected stream condition based on Urban Intensity of watershed

6

Acme Chemical Site

  • Urban Intensity = 40
  • Stream Condition = 2.5

5

4

Taxa Tolerance

(Expected)

3

2

1

0

0

40

60

80

100

20

Urban intensity

expected stream condition based on urban intensity of watershed3
Expected stream condition based on Urban Intensity of watershed

6

Acme Chemical Site

  • Urban Intensity = 40
  • Stream Condition = 2.5

CONCLUSION

No unacceptable

ecological risk

5

4

Taxa Tolerance

(Expected)

3

2

1

0

0

40

60

80

100

20

Urban intensity

expected stream condition based on urban intensity of watershed4
Expected stream condition based on Urban Intensity of watershed

6

Acme Chemical Site

  • Urban Intensity = 40
  • Stream Condition = 4.5

CONCLUSION

Stream condition

may be affected by

site contamination.

5

4

Taxa Tolerance

(Expected)

3

2

1

0

0

40

60

80

100

20

Urban intensity

concluding points
Concluding Points
  • Study currently being funded by EPA Region I (New England) to use this approach, which is expected to improve Ecological Risk Characterizations.
  • Even a general awareness of the urban intensity of a basin is useful in making an interpretation of stream condition at a site.