how to improve the functionality and resilience of ... · • constructed wetlands located in more...
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How to improve the functionality and resilience of constructed stormwater wetlands
Jason Martin, PhDEnvironmental Manager
Aqualis Stormwater Management
Suzanne Beyeler, PhDDirector of Environmental Studies
Manchester University
Background
What is “compensatory mitigation”?
• Clean Water Act regulates impacts to natural wetland habitat
• Mandates replacement of functionality
• Preference for mitigation located at impacted site; typically in development zone
Background
Background
Background
Background
What is “compensatory mitigation”?
• “Success” defined using measurable performance standards:– % survivorship of planted species
– % cover of native and/or invasive plants
– % cover obligate/facultative wetland plants
Background
What is “compensatory mitigation”?
• “Success” defined using measurable performance standards:– % survivorship of planted species
– % cover of native and/or invasive plants
– % cover obligate/facultative wetland plants
• Performance standards not tied to replacement of functionality
Background
What is “compensatory mitigation”?
• Structure is not a precursor to wetland functionality
• Functionality gives rise to and maintains structure
Background
Does wetland mitigation work?
• Only 30% of wetlands constructed in IL meet all compliance goals (Matthews
& Endress, 2008)
• Up to 87% of wetlands constructed in Indiana fail (IDEM, 2001)
• Planted vegetation doesn’t grow; dominant vegetation weedy exotic species (Matthews & Endress, 2008)
Background
Does wetland mitigation work?
Background
Context is the key to functionality
Background
Context is the key to functionality
Background
What is the role of landscape context for stormwater wetlands?
Hypothesis
Constructed wetlands in natural landscapes have greater ecological functionality than those in urbanized or agricultural landscapes.
• Reflected in chemistry, vegetation, and macroinvertebrates
Ecological functionality = regulatory compliance and long-term maintenance efficiencies
Methods
Study sites
Indiana Ohio
Michigan
Illinois
• 2017 & 2018
• 19 total sites
• All > 5 years old
• All “successful”
• Basin sizes: 0.1 – 2.5 ha (avg. = 1 ha)
Methods
Landscape-scale metrics
• 2-km buffers around each study wetland
2011 Land Cover & Canopy Closure• % Forest• % Agriculture• % Developed (excluding open space)
National Wetlands Inventory• Total area of wetlands• Distance to nearest wetland• Mean and median wetland area• Total # wetlands
ArcGIS 10.4.1
Methods
Study sites
• Selected across gradient of landscape contexts
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GB JE NL
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Study Sites
Developed Area
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GB JE MI
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Study Sites
Agricultural Area
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Study Sites
Natural Area
Methods
Other data
Soil chemistry• 2018 – 6 cores per wetland; homogenized • % Organic matter, pH, P, K, Mg, Ca, S, Zn, Mn, Fe, Cu, B, Cl
Water chemistry• 2017-2018 – Collected 9 times per wetland per year• pH, NO3, PO4, Cl
Vegetation• Meander survey & modified Braun-Blanquet method
Macroinvertebrates• 2-min sweep net collection in emergent & submerged
vegetation zones (standardized sample areas)• 6 zones per wetland• Individuals identified to taxonomic Family
Results
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Cl (
pp
m)
Species Richness
Chloridey=-18.48x+604.2R=0.31p=0.03
Wetland soil chemistry effects on wetland vegetation
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Zn (
pp
m)
Species Richness
Zincy=-0.41x+13.16R=0.44p=0.01
Results
Chemistry effects on macroinvertebrates
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Zn (
pp
m)
Family Richness
Zincy=-0.35x+13.61
R=0.22p=0.07
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Cl (
pp
m)
# Amphipoda / 25 m2 / 2 min
Chloride
y=-2.56x+332.8R=0.31p=0.04
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Cl (
pp
m)
# Ephemeroptera (Mayflies) / 25 m2 / 2 min
Chloride
y=-5.45x+354.2 R=0.20p=0.09
Results
t=3.56, p=0.01 t=2.03, p=0.04
Surface runoff effects on chemistry
Results
Landscape-scaleInfluence on wetland vegetation
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# Sp
ecie
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% Developed Area in 2km2
Obligate Wetland Vegetation
y=-0.14x+20.01R=0.29p=0.04
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# Sp
ecie
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% Developed Area in 2km2
Submerged Vegetationy=-0.05x+5.54R=0.31p=0.03
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0 5 10 15 20
# Sp
ecie
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% Forest Area in 2km2
Obligate Wetland Vegetation
Results
Landscape-scaleInfluence on wetland vegetation
y=0.74x+10.08R=0.21p=0.08
Conclusions & Next Steps
• Urban landscape stressors (e.g., parking lot runoff carrying zinc & chloride) negatively impact functionality of mitigated wetlands
Conclusions & Next Steps
• Urban landscape stressors (e.g., parking lot runoff carrying zinc & chloride) negatively impact functionality of mitigated wetlands
• Constructed wetlands located in more natural landscape contexts seem to support greater biodiversity
Conclusions & Next Steps
• Urban landscape stressors (e.g., parking lot runoff carrying zinc & chloride) negatively impact functionality of mitigated wetlands
• Constructed wetlands located in more natural landscape contexts seem to support greater biodiversity
• This suggests that landscape context is important when selecting locations of new mitigation sites
Conclusions & Next Steps
• Urban landscape stressors (e.g., parking lot runoff carrying zinc & chloride) negatively impact functionality of mitigated wetlands
• Constructed wetlands located in more natural landscape contexts seem to support greater biodiversity
• This suggests that landscape context is important when selecting locations of new mitigation sites
• Knowledge of landscape context can also help guide creation of management goals and prioritize management action
Conclusions & Next Steps
• Create predictive spatial model for:
– Selecting locations for wetland mitigation projects that have highest likelihood of achieving regulatory compliance
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Conclusions & Next Steps
• Create predictive spatial model for:
– Selecting locations for wetland mitigation projects that have highest likelihood of achieving regulatory compliance
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– Guiding and prioritizing management actions of existing constructed wetlands and allocation of related resources
Acknowledgements & Questions
Logistical support and site access provided by Walmart Inc., Michigan Department of Environmental Quality, Michigan Department of Transportation, Dundee Township (IL), and Openings Wetland Mitigation Bank.
Special thanks to Manchester University: Dr. Suzanne Beyeler, Nolan Sipe, Tristan Barley, Josh Melton, Corey Rowland, and Amy Weeks
Jason MartinAqualis Stormwater Management
Suzanne BeyelerManchester University