Date post: | 01-Jan-2016 |
Category: |
Documents |
Upload: | buddy-moody |
View: | 298 times |
Download: | 24 times |
Ecological responses of streams to urbanization: A review of
results from the U.S. Geological Survey's urban streams studies
North Carolina Water Science Center
Thomas F. Cuffney
North Carolina Water Science Center
Raleigh, North Carolina
Boston
Birmingham
Salt Lake City
Raleigh
Atlanta
Seattle
Portland
Sacramento Denver
Dallas-Ft. Worth
Milwaukee-Green Bay
National Water-Quality Assessment (NAWQA) Program 11 Urban Stream Studies
Raleigh Urban Study AreaPiedmont
Objectives:1. Define biological, physical, and chemical
responses to urbanization across conterminous US.
2. Identify the primary environmental factors associated with these responses.
3. Compare how responses and driving factors change across the US.
-- What measures best depict urban effects (monitoring)?
– What factors can be changed to mitigate urban effects (planning and remediation)?
– Can urban effects be managed using national criteria or are regional or local criteria required (management and legislation)?
Representing urban intensity: urban intensity index (UII)
Index based on land-cover, population, infrastructure and
socioeconomic factors correlated with changes in population density
Urban variables positively correlated with population density
East Central West
Variable Atlanta Raleigh Dallas Milwaukee Denver Portland
Household density X X X X X X
Density of housing units X X X X X X
Road density X X X X X X
Urban lands in basin (%) X X X X X X
Impervious surface (% basin) X X X X X X
Popl'n in urban areas (%) X X X X X X
Urban lands in riparian (%) X X X X X X
Impervious surface (% riparian) X X X X X X
Housing - utility gas (%) X X X X X
Housing - renter occupied (%) X X
East Central West
Variable Atlanta Raleigh Dallas Milwaukee Denver Portland
Popl'n in rural area (%) X X X X X X
Heat with LP gas (%) X X X X X X
Heat with wood (%) X X X X X X
Forest (% basin) X X X
Shrubland (% basin) X X X X
Grassland (% basin) X X X X
Ag/pasture (% basin) X X X
Forest (% riparian) X X X
Shrubland (% riparian) X X X
Ag/pasture (% riparian) X X X
Urban variables negatively correlated with population density
Urban intensity index (UII)
Raleigh Example:
Census variables: 2000 population density Household density National Land-cover Data: % of basin in developed lands % of stream buffers in developed lands Infrastructure: road density
% Impervious and Urban Intensity index (UII) -- Atlanta
y = 0.0014x2 + 0.1865x + 0.0125
R2 = 0.93
0
5
10
15
20
25
30
35
40
45
0 20 40 60 80 100
Urban intensity (UII)
% im
per
vio
us
Urban intensity (UII) at 10% impervious surface
0
10
20
30
40
50
60
Atl
anta
Bir
min
gh
am
Bo
sto
n
Ral
eig
h
Dal
las
Den
ver
Milw
auke
e
Po
rtla
nd
Sal
t L
ake
Urb
an in
ten
sity
(U
II)
0.95
0.88
0.950.78
0.92
0.92 0.88 0.95
0.83
Biological responses to urbanization
Fish, Invertebrates, and Algae
Expected response
0
20
40
60
80
100
120
0 10 20 30 40 50 60 70 80 90 100
Urban intensity (UII, % impervious)
Res
po
nse
var
iab
le
Exhaustion
Resistance
Maximum rate of change
(≈ 10 % impervious surface)
Bio
log
ical
co
nd
itio
n
Good
Poor
Urban intensity (UII)
Atlanta urban model (Piedmont)
y = -0.0169x + 1.6651R2 = 0.81
0.0
0.5
1.0
1.5
2.0
2.5
0 20 40 60 80 100
Urban intensity index (UII)
Ord
inat
ion
sco
re (
axis
1)
Typical response (Inverts Atlanta)
10% impervious surface
40% of total change
Inve
rteb
rate
res
po
nse
Boston Fish: Exhaustion
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 10 20 30 40 50 60 70 80 90 100
Urban intensity (UII)
Axi
s 1
site
sco
reF
ish
res
po
nse
Urban intensity (UII)
Invertebrates responses to urbanization (Y = a + b*UII) across US
Region City b R2 PEast
Atlanta -0.017 0.70 < 0.001Birmingham -0.017 0.63 < 0.001Boston -0.017 0.82 < 0.001Raleigh -0.016 0.73 < 0.001
CentralDallas/Fort Worth -0.007 0.16 0.023
Milwaukee -0.009 0.20 0.007
WestDenver -0.007 0.22 0.008Salt Lake City -0.015 0.47 < 0.001
Portland -0.016 0.57 < 0.001
Invertebrates responses to urbanization (Y = a + b*UII) across US
Region City b R2 PEast
Atlanta -0.017 0.70 < 0.001Birmingham -0.017 0.63 < 0.001Boston -0.017 0.82 < 0.001Raleigh -0.016 0.73 < 0.001
CentralDallas/Fort Worth -0.007 0.16 0.023Denver -0.007 0.22 0.008
Milwaukee -0.009 0.20 0.007
WestSalt Lake City -0.015 0.47 < 0.001
Portland -0.016 0.57 < 0.001
0
20
40
60
80
100
Atla
nta
Bir
min
gh
am
Bo
sto
n
Ra
leig
h
Da
llas
De
nve
r
Milw
au
kee
Po
rtla
nd
Sa
lt L
ake
% B
asin
are
a
Land cover at “background” sites: UII < 20
Forest + shrublandsAgriculture + grasslands
EAST CENTRAL WEST
% B
asin
are
a
Agriculture
Irrigation?Grazing?
Summary of biological responses to urbanization (UII)
• Significant relation between urban intensity and biological degradation.
– Invertebrates are the strongest and most consistent indicators.
– Algae and fish responses are more variable.
– Relations were strongest when urbanization involved conversion of forest or shrub lands.
– Relations were weakest when urbanization involved conversion of agricultural or grass lands.
• Little evidence for resistance to urbanization (no initial threshold).
Changes in water chemistry associated with urbanization and
biological responses
Chemical trends with urbanization
• Conductivity
• Pesticides:– Number detected
– Total concentration
– Pesticide index
• Nutrients:Chemistry Invertebrates
Chemical trends with urbanization (continued)
• Polycyclic aromatic hydrocarbons (PAH):
– Number detected
– Total concentration
• Very few instances where human or aquatic life standards were exceeded.
• Relations with urbanization were also affected by presence of agriculture and grasslands (Central: Dallas, Denver, Milwaukee).
Chemistry Invertebrates
Hydrologic changes associated with urbanization and biological
responses
Relations with
Hydrologic change
Invertebrate condition
Increasing urbanization
Flow variability
Duration of high flows
Key Findings from Urban Studies
1. Degrades biological communities:a. Invertebrates are “best” biological indicator.
b. No level of urbanization without an effect.
2. Increases chemical contamination:a. Number and conc. of pesticides.
b. Number and conc. of PAH’s.
3. Modifies hydrologya. Increases flashiness.
b. Decreases duration of peak flows in many urban areas, but not all.
Key Findings (continued)4. Factors associated with urban degradation that may
be useful for mitigation:a. Decrease effects of road density in basin.
b. Decrease effects housing density in basin.
c. Restore forest and shrub lands (basins and buffers).
d. Restore connection between precipitation, ground water, and surface water (restore normal hydrology).
5. Responses vary geographically: a. East = West in biological (invertebrate) responses.
b. = Central (agriculture + grasslands).
c. Extent of “background” degradation affects how biology and chemistry respond to urbanization.
d. Regional approaches to management and legislation may be required.
/