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Infrastructure Resiliency Planning:
Keeping Downtown Economies Strong
Best Practices for Assessing Climate Risk
from Extreme Rainfall Events
Laurens van der Tak
1
Today’s discussion
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Why Consider Climate Risk for Downtown Facilities
Climate Risk – a Primer
Climate Scenarios and Uncertainty
Examples
Why consider climate change for infrastructure planning and
design?
 Road drainage, stormwater and wastewater facilities typically are designed
for selected peak design storms, estimated based on historical records
 Extreme events consistent with climate change could alter these design
criteria resulting in significant over- or under-design of facilities, creating
unnecessary capital expense, or non-compliance with permits, and
significant economic damage to communities
Businesses close as Duluth faces historic flooding
Minneapolis / St. Paul Business Journal
June 20, 2012
What are extreme rainfall events?
 Consensus definition: events that are
“rare”
 When they occur, can have catastrophic
effects on human activities,
infrastructure, and the environment
Orchard Road,
Singapore
Source: Paul Davies, UK Met Office, 2009
Extreme rainfall events are becoming more frequent

Louisville, KY 2009: 5” in 90
minutes (1000-yr return interval is
3.83”/hour)
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Washington, DC 2006: 11.3” in 6
days
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Chicago, IL 2008: 6.7”in 1 day
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Atlanta, GA 2009: 13” in 1day
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Nashville, TN 2010: 13.6” in 2days
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Duluth, MN, 2012: 10” in 1 day
Increases in Amounts of Very Heavy
Precipitation 1958 to 2007 (USGCRP 2009)
What do these changes mean for facility planners:
What future conditions will affect the function of our downtown infrastructure and
what questions should planners ask:
 Will changing storm frequencies change design storm criteria for transportation
and stormwater conveyance facilities?
– Could a "10-yr" storm be expected to become a "2-yr storm“?
– What liabilities could result from these changes?
 Will rising sea level impact facility
siting and sizing?
- Is your outfall going to be partially or fully
-
submerged more often?
Will your facility need to be flood-proofed or
moved?
Climate risk is just one among multiple risk factors to evaluate
likelihood and consequence of facility failure
High
Future Climate Risk
Probability
Existing Risk
Reduced Risk
Net Future Risk
Other
Future
Risk
Low
Low
Consequence
High
How do we ID and address these risks: Create future plausible
scenarios and consider uncertainty: which GCMs, GHGs, and
planning horizons???
Planning process should recognize that most underground infrastructure is
expected to have a service life of 100 years or more, so consider:
 Other plausible changes in the environment that could affect facility function
– population, land use, possible technology changes, possible changes in regulations,
 Projected climate change
– climate in long term (2100 or later), or, climate in near term (2030-2050), can the facility
capacity can be expanded in phases
 Creating portfolios of “no regrets” options that are customizable for range of
possible future scenarios:
– source control through green infrastructure, appropriate grey infrastructure, land use
planning, building codes that include flood proofing
Select a range of GHG emission scenarios to envelope or bookend
potential climate uncertainty, ID suitable GCMs/ensembles (IPCC)
“Scenario Family”
Description
A1 – Rapid Growth
A1FI - Fossil Intensive
A1T - Non-fossil
A1B – Balanced
Second Highest
Greenhouse Emissions
A2 – Heterogeneous
High Population Growth
Slow Economic and
Technology Change
Highest Greenhouse
Emissions
B1 – Convergent World
Same Population as A1,
more service and
information technology.
Lowest Greenhouse
Emissions
A1FI
A2
A1B
B2
A1T
B1
B2 – Intermediate
Population growth, local
solutions.
Second Lowest
Greenhouse Emission
Scenarios for GHG emissions from 2000 to 2100 in the
absence of additional climate policies. (IPCC 2000)
How do we defensibly and efficiently translate global climate
science to local impacts and wet weather planning action
Global Information
• Changing Climate science
• General Circulation Models
• Emission Scenarios
• lmpact assessment
• IPCC Assessment Reports
Local Concerns
• Defensible risk assessment
• Temp and precip change
• Catastrophic events
• Sea level change
• Adaptation effectiveness
• Cost and timing
Globalregional
scale
Climate science
and scientists
operate at
global scale
Large gap
Localnational
scale
Impacts, planning, and
action are local
A solution: a modeling environment to bridge the gap between
global climate science and local impacts and action: SimCLIM
Globalregional
scale
Globalregional
scale
Localnational
scale
Localnational
scale
 SimCLIM—an integrated modeling
system for assessing climate conditions
that influence risk and resilience for built
and natural infrastructure and operations
 Considers plausible, customized future
scenarios for water, sea level and coastal
issues, human health, ecosystems,
agriculture, transportation, energy, and
others
 Incorporates local data for consideration
of local impacts
Storm sewer infrastructure planning with climate change risk:
A Case Study—Alexandria Virginia
 Experiencing repeated and increasingly
frequent flooding events
 Review of stormwater design criteria
and projected impacts of climate
change
 Using SimCLIM projections and post
processing for 2050 and 2100 to assess
sea level rise; and rainfall intensity,
duration, and frequency
 Evaluating infrastructure adaptation
options to reduce impacts from sea level
rise and flooding from more intense and
frequent storms
Hurricane Isabel flooding, September 2003
Photo Credit: Mark Young/The Journal Newspapers
Projected Annual Precipitation (Reagan National Airport, DC)
Reagan National Airport Projected Annual Precipitation
Median from 5 GCMs, 3 SRES Emissions (B1, A1B, A1FI)
60.00
55.9”
+44%
Annual Precipitation (Inches)
55.00
Median 5 GCM B1 (Low) Emissions
Median 5 GCM A1B (Medium) Emissions
Median 5 GCM A1FI (High) Emissions
52.2”
+35%
50.00
47.3”
+22%
45.00
40.00
38.8”
35.00
1990
2000
Total Precipitation projected to increase by 22 to 44% 2010
2020
2030
2040
2050
Year
2060
2070
2080
2090
2100
Alexandria Virginia: Change in Rainfall Frequency
Daily Rainfall Extremes – Intensity and Frequency
A1FI (highest), 12 GCMs
The intensity of a 10 year
event will be 15% higher by
2050
Best practices for assessing climate risk from extreme rainfall
events for drainage infrastructure and downtown businesses
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Consider range of plausible futures and risks
Integrate climate risk with overall risk assessment
Recognize service life of infrastructure
Consider uncertainty by factoring in:
– An envelope of GHG emission scenarios (low, medium, or medium-high, high)
– A range of GCM models (downscaled to project scale)
 Use a science-based, updatable, efficient tool set to implement this
approach for defensible outcomes and implementable solutions
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Options for building resilience
 Planning
 Avoidance
 Green Infrastructure
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–
–
–
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Green Streets & Alleys
Green Parks
Green Parking Lots
Vegetated Roofs
Enhanced Tree Planting
Green Schools & Public Facilities
 Detention Systems
 Flood proofing
 Emergency preparedness
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Permeable pavement options fit into downtown streetscapes
Detention systems can be multifunctional in downtown urban areas
Storage Pond used to Attenuate Storm Run-off
in a New Development in Netherlands.
Dual-use Detention Storage Area in an Urban
Community in Malmo, Sweden
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Floodproofing can protect high value assets from infrequent
but potentially damaging floods
Retrofitted rising flood barriers along
Orchard Road, Singapore.
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Source: Climate Adaptation and Transportation, CCAP, May 2012
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Infrastructure Resiliency Planning:
Keeping Downtown Economies Strong
Best Practices for Assessing Climate Risk
from Extreme Rainfall Events
Laurens van der Tak
22