Climate change. What impact will it have on infrastructure? And how can we plan for the next 50 to 100 years, today? OHM Advisor’s [http://www.ohm-advisors.com] Charles Humpriss, PE, gave a presentation at the Michigan Water Environment Association’s Watershed Seminar, Tangible Approaches to Quantify Climate Change for Infrastructure Planning and Design. In it, he talked about a recent update to the EPA’s National Stormwater calculator, a free online modeling tool that estimates the annual amount of rainwater and frequency of runoff from a specific site based on local soil conditions, land cover, and historic rainfall records. The new update adds a Climate Adjustment tool that lets engineers and planners evaluate the impacts of future climate change projections on water infrastructure performance. Some of the scenarios include more frequent high intensity storms and changes in evaporation rates of seasonal precipitation. Scenarios: • Hot/Dry • Median Change • Warm/Wet The Climate Adjustment Tool also includes the ability to apply scenario projections to the near term (2020-2049) and far term (2045-2074.) showing how the different far term scenario projections affect monthly rainfall levels and extreme storm events. Sanitary sewer analysis Hydraulic engineers from OHM Advisors used the Climate Adjustment Tool to help the City of Ann Arbor evaluate future capacity needs for its sanitary sewer system. As part of a sanitary sewer wet weather evaluation study, the project team evaluated several scenarios and ran models for each, to determine the impact on the sanitary infrastructure. In using the tool to evaluate Ann Arbor’s sanitary sewer system, the team observed that the Warm/Wet scenario results in higher average rainfall, while the Hot/Dry scenario produces slightly larger extreme storms. The hydraulics engineers performed a Frequency Analysis using Hydrologic Model Output and 60 years of historic rain data to analyze the frequency of storms with the potential to overwhelm the City’s wastewater treatment plant. Ultimately, the project team, which included a advisory committee of involved citizens, elected to use a 10% increase in future peak flow rates, to account for climate change. A Technical Oversight and Advisory Group, which included nationally recognized authority on climate change impacts on landscape ecology, Dan Brown, of the University of Michigan, reviewed the project team’s recommendations: “…TOAG Members indicated that the recommendation to increase the 25 year Design Event flow rate by 10% is reasonable since this is a mid-range value which falls near the center of the climate change forecast models showing “best case” and “worst case” future conditions…”

1. OHM-ADVISORS.COM
Tangible Approaches to Quantify
Climate Change for Infrastructure
Planning and Design
Charles Humphriss
OHM Advisors
MWEA Watershed Seminar
December 3, 2014
ARCHITECTS. ENGINEERS. PLANNERS.

2. OHM-ADVISORS.COM ARCHITECTS. ENGINEERS. PLANNERS.
EPA Stormwater Calculator
http://www2.epa.gov/water-research/national-stormwater-calculator
Estimates annual
amount of
rainwater &
frequency of
runoff from a
specific site based
on local soil
conditions, land
cover, and historic
rainfall records.

3. OHM-ADVISORS.COM ARCHITECTS. ENGINEERS. PLANNERS.
EPA Stormwater Calculator:
Climate Change Options
http://www2.epa.gov/water-research/national-stormwater-calculator
• Scenarios:
 Hot/Dry
 Median Change
 Warm/Wet
• Time Period:
 Near Term
(2020-2049)
 Far Term
(2045-2074)

4. OHM-ADVISORS.COM ARCHITECTS. ENGINEERS. PLANNERS.
EPA Stormwater Calculator:
Ann Arbor Example
http://www2.epa.gov/water-research/national-stormwater-calculator
Applying
Rainfall
generated
to a
Sanitary
Sewer
Analysis

5. OHM-ADVISORS.COM ARCHITECTS. ENGINEERS. PLANNERS.
EPA Stormwater Calculator:
Ann Arbor Example
http://www2.epa.gov/water-research/national-stormwater-calculator
Far Term
(2045-2074)
Warm/Wet
Scenario

6. OHM-ADVISORS.COM ARCHITECTS. ENGINEERS. PLANNERS.
EPA Stormwater Calculator:
Ann Arbor Example

7. OHM-ADVISORS.COM ARCHITECTS. ENGINEERS. PLANNERS.
EPA Stormwater Calculator:
Ann Arbor Example
Perform
Frequency
Analysis
using
Hydrologic
Model
Output and
60 years of
historic rain
data

8. OHM-ADVISORS.COM ARCHITECTS. ENGINEERS. PLANNERS.
EPA Stormwater Calculator:
Ann Arbor Example
Perform
Frequency
Analysis
using
Hydrologic
Model
Output and
60 years of
hourly
historic rain
data

9. OHM-ADVISORS.COM ARCHITECTS. ENGINEERS. PLANNERS.
EPA Stormwater Calculator:
Ann Arbor Example
Perform a
second
Frequency
Analysis using
Hydrologic
Model Output
and 60 years
of hourly rain
data scaled
monthly using
output from
EPA’s SW
Calculator
10%
increase for
25-yr storm

10. OHM-ADVISORS.COM ARCHITECTS. ENGINEERS. PLANNERS.
EPA Stormwater Calculator:
Ann Arbor Example
• Consider a 10% increase in peak flows to account for
climate change.
• Technical Oversight and Advisory Group (TOAG) quote:
…TOAG Members indicated that the
recommendation to increase the 25 year Design
Event flow rate by 10% is reasonable since this is
a mid-range value which falls near the center of
the climate change forecast models showing
“best case” and “worst case” future conditions…