A Traditional vs. Ecosystem Services
Approach to Surface Water
Management
September 16, 2010
WBG052710054733PDX 349800.GS.01.02 60110 kk
PRESENTED BY
Carol Murdock, Clackamas County WES
Mark Anderson, CH2M HILL
Introduction / Context
• Ecosystem Services Approach to Facilities Planning – City
of Damascus, OR
• How are we defining Ecosystem Services?
• Could an ES services approach be cost effective in the
long-term?
• Business Case Evaluation – cost/benefit analysis
– Environmental benefit – regulatory compliance
– Community – livability, healthy environment
– Economic – lower long-term cost to ratepayers, economic
growth
• WES - Intent of BCE – inform policy decisions; develop
implementation mechanisms; provide information on
long-term cost savings
Clackamas County, Oregon – Rock Creek basin
Pilot Study Area
Rock Creek Basin
Graphics courtesy Wikimedia,
Clackamas County Service District #1
Rock Creek Watershed Action Plan,
Brown and Caldwell
Rock Creek basin has 4 major ecosystem types
Deciduous/Mixed Deciduous Forest
Evergreen Forest
Riparian Forest/Streams
Wetlands
Mapped Ecosystem Extent and Quality
Methods of managing urban ecosystems for
stormwater treatment are not new
•
•
•
•
Riparian Buffers
Conservation areas
Vegetated filter strips
Overland flow systems (NTS design)
The key for basin planning is balancing land
resources
• Ecosystems require land area but offer two benefits:
– “Passive” benefits when land zoned for development is
preserved.
– “Active” benefits when ecosystem land manages runoff from
development.
• When land area is treated as a “facility”, public support
and decision-making are essential
Active Benefits: RUSA meets TMDL limits for
Roseburg wastewater discharge
• Similar ecosystem mix to
Clackamas County
• Up to 70% slopes down to
gentle slopes with a creek in
incised valley bottom
• Minimal changes to existing
ecosystem were required to
provide adequate treatment
• DEQ-approved facility at
10% of the cost of built
infrastructure
.
We propose an integrated planning approach…
Prioritization of Stormwater
Control Strategies to Meet
Level of Service Goals
PRIORITY STRATEGY 1.
Use ecosystem services
of protected areas
PRIORITY STRATEGY 2.
PRIORITY STRATEGY 5.
Implement built
infrastructure
Reduce development
footprint
PRIORITY STRATEGY 4.
PRIORITY STRATEGY 3.
Maximize LID stormwater
controls
Uplift
…that meets Level of Service goals
Prioritization of Stormwater
Control Strategies to Meet
Level of Service Goals
PRIORITY STRATEGY 1.
Combined 5 Strategies
= Total Stormwater
Management Solution
Use ecosystem services
of protected areas
PRIORITY STRATEGY 2.
PRIORITY STRATEGY 5.
Reduce development
footprint
Implement built
infrastructure
LOS Met
PRIORITY STRATEGY 4.
PRIORITY STRATEGY 3.
Maximize LID stormwater
controls
Uplift
A business case identifies credible strategies that compare
to conventional runoff management
PRIORITY STRATEGY 1.
Use ecosystem
services of protected
areas
PRIORITY STRATEGY 2.
PRIORITY
STRATEGY 5.
Implement built
infrastructure
PRIORITY STRATEGY 4.
Maximize LID
stormwater controls
Reduce development
footprint
LOS Met
Strategy 5.
Business as Usual
LOS Met
PRIORITY STRATEGY 3.
Uplift
We use a mix of conventional models and new
resource balance concepts
• Simple Method (runoff and pollutant load)
• TR-55 (peak flows)
• Clackamas County Pollutant Loadings Model
• A new land balance tool to manage ecosystem and
development area flow and load trade-offs
• A new cost calculator that relates infrastructure, land,
restoration, and ecosystem value to find efficient
strategies
Pilot study area characteristics – 167 acres
2%
14%
Butte Residential
5%
Rural Residential
9%
Neighborhood Low
50%
Neighborhood Medium
15%
Village Employment
5%
Village
Village Core
28
17%
100
60%
39
23%
0
0%
Forest
Riparian
Wetlands
Non-Native/Non-built
Summary of preliminary results
Strategy 3.
Uplift, 1%
Strategy 4.
Maximize
LID
stormwater
controls;
17%
TSS (LOS = 90% volume to 70% removal)
Strategy 1.
Use
ecosystem
services of
protected
areas; 66%
Strategy 3.
Uplift and
use
ecosystem
services of
uplifted
areas; 9%
Strategy 2.
Reduce
developmen
t footprint;
16%
Strategy 2.
Reduce
development
footprint;
37%
Runoff (LOS = 2x existing)
Strategy 1.
Use
ecosystem
services of
protected
areas; 59%
Stormwater function by ecosystem type
Existing condition/LOS
Zoned development (1 acre)
Difference - amount that needs
to be managed by stormwater
system
100-year flood
volume (gallons)
Annual Runoff Volume
(gallons)
100-year Peak flow (cfs)
TSS load (lbs)
83,343
117,251
164,216
549,114
0.4
0.6
63
171
33,908
384,898
0.2
108
Acres required to manage difference shown above
Evergreen Forest A
N/A
Evergreen Forest B
N/A
Evergreen Forest C
N/A
2.5
2.7
2.9
3.5
3.6
4.0
0.9
0.9
0.9
Deciduous Forest A
Deciduous Forest B
Deciduous Forest C
N/A
N/A
N/A
2.5
2.7
2.9
3.5
3.6
4.0
0.9
0.9
0.9
Riparian corridor A
Riparian corridor B
Riparian corridor C
0.4
0.4
0.4
2.5
2.7
2.9
3.5
3.6
4.0
0.9
0.9
0.9
Wetlands A
Wetlands B
0.4
0.4
0.1
0.1
<0.4
<0.4
N/A
N/A
Non-native/non-built
N/A
4.1
5.0
0.9
Some early results
• About 3 acres of natural area will manage impacts from 1
acre of residential development, depending on zoning
• Uplift has little effect on treatment, but more important
for volume – heavily dependent on assumptions
• Ecosystem areas can be valued monetarily to help drive
market behavior.
• Assumptions about density and EDU buildout are highly
sensitive
General site design considerations
•
•
•
•
Pre- and post-developed time of concentration
Typical slope
Limits of treatment area (due to topography, etc.)
Expected treatment infiltration loss (derived from
ClackCo model)
• Expected pollutant capture rate
• Treatment area characteristics and effectiveness
Potential avenues for research and development
• Treatment effectiveness in varied natural conditions
• Infrastructure costs
• Uplift costs
Planned next steps
• Develop alternatives for BCE and policy selection
• Refine and implement planning framework for Damascus
• Engage with stakeholders to think about resource
economics in a new way
Acknowledgements
• City of Damascus, Oregon
• Oregon Department of Environmental Quality
WBG052710054733PDX 349800.GS.01.02 60110 kk
Questions or Comments?