Climate Change Preparedness of Great Lakes Communities: Regulatory Permits & Community Planning are Based on Outdated Precipitation Data

The below is taken from the Executive Summary of the report “Climate Change Preparedness of Great Lakes Communities”, an evaluation of whether regulatory permits and community planning efforts are current and aligned to manage climate change-driven increases in rainfall.

Changing rainfall amounts across five cities in the Great Lakes region were examined to understand whether the regulatory permits and community planning efforts are aligned with robust and current rainfall estimates. Rainfall amount is a key factor considered in stormwater and sewer infrastructure design and dictates the cost of infrastructure as well as its performance. Over the last few decades, agencies and jurisdictions responsible for infrastructure, including storm and combined sewer infrastructure (much of which was constructed decades ago) have anecdotally reported that event precipitation amounts (“Precipitation Frequency Estimates” or PFEs) have increased significantly.

Cities across the region have suffered accordingly. Detroit, for example, suffered massive flooding in 2014, 2016, 2019, and 2021, causing economic, environmental, psychological, public health, and financial hardship on residents and businesses. Further, these floods damaged public facilities, museums, and schools across the city. These trends are unfortunately not unique to Detroit, and rampant flooding is now a common occurrence across Great Lakes cities. Finally, forecasts of future event precipitation amounts are significantly more than what they are today, suggesting the impacts of storms and the resulting damages will continue to get worse.

This report’s focus is on Milwaukee (Wisconsin), Chicago (Illinois), Detroit (Michigan), South Bend (Indiana), and Buffalo (New York). For the purposes of analyses, the specific geography for each metro area was defined by the service area of their respective water/wastewater utility/agency.

Among our findings, all five wastewater facilities were issued their permits well before the National Oceanic & Atmospheric Administration (NOAA) and Illinois State Water Survey (ISWS) published their most recent precipitation estimates. In other words, wastewater systems were designed to meet past climate trends. While some agencies now require designs based on more recent precipitation estimates, system-wide investments and updates take time and many systems no longer have capacity to meet the needs of our current climate.

Our analyses also found that in most locations, there is little change in the 10-year PFE from historical (1961) to current (2019-2020 timeframe), except in the Chicago region that shows a dramatically large change from the 1961 data. In all cases, the 100-year PFE increased, with increases varying from 11% more rain in Milwaukee to 50% increase in Chicago (Tables 1 through 4).

So far as future projections, for the mid- (and late-) century estimates, both the 10-year and 100-year PFE are expected to increase over the current values. For 10-year events:

In Detroit: The rainfall amount is expected to increase by 67% by mid-century, and 138% by the end of the century. These are massive changes.
In Chicago: The rainfall amount is expected to increase by 15% by mid-century, and 20% by the end of the century.
In Buffalo: The rainfall amount is expected to increase by 10% by mid-century, and 21% by the end of the century.

Part of the challenge is that every city is using different sources for their climate change estimates. For example, Chicago’s estimates were based on the ISWS and, to some degree, ISWS already built climate change into their reporting and therefore show less future change.

For 100-year events:

In Detroit: The rainfall amount is expected to increase by 19% by mid-century, and over 97% by the end of the century. These are massive changes.
In Chicago: The rainfall amount is expected to increase by 15% by mid-century, and 20% by the end of the century.
In Buffalo: The rainfall amount is expected to increase by 22% by mid-century, and 30% by the end of the century.

Key recommendations from this report are below:

Combined Sewer Overflow (CSO) permits need to be updated
That “data stationarity” is not relevant anymore, needs to be communicated and accepted among decision makers
Legislative reforms are needed to incorporate future climate data
Legislative reforms are also needed for communities to work closely with the private sector insurance industry
Alternatives to grey infrastructure must continue to be leveraged at large-scale
Options to make existing/future water (green or grey) infrastructure more efficient
Water management strategies must continue to be implemented via public education
Emphasis on upgrading infrastructure must be continued
Funding for water infrastructure in general and green stormwater infrastructure in particular must be dramatically increased

Overall, the current and projected increases in PFEs for much of the Great Lakes region’s infrastructure are dramatic, and clearly demonstrate the need for investments in infrastructure that are made for mid-century and beyond.

Download the full report here.