May 27, 2024

Today’s MI Environment story by Christe Alwin, a supervisor of EGLE’s Water Resource Division’s Stormwater Permits Unit, is from the State of the Great Lakes report.

During a single August 2023 storm, more than five inches of rain pounded Southeast Michigan, flooding roads, closing routes to Detroit Metropolitan Airport, and prompting a declared state of emergency. Such events are no longer so rare in Michigan.

Nearly five inches of rain washed out this road in Southeast Michigan’s Washtenaw County in an August 2023 storm. Courtesy of Washtenaw County Road Commission.

Nearly five inches of rain washed out this road in Southeast Michigan’s Washtenaw County in an August 2023 storm. Courtesy of Washtenaw County Road Commission.

 

As noted in the state’s MI Healthy Climate Plan, Michigan in a time of climate change is experiencing historic levels of rain and intense storms that will lead to continued property loss and infrastructure failures. According to Great Lakes Integrated Sciences and Assessments, annual precipitation in the Great Lakes region has increased by 17% since 1951. Climate models project the region will experience a greater increase in total precipitation than most other regions in North America.

The Michigan Department of Environment, Great Lakes, and Energy’s (EGLE) Water Resources Division (WRD) is wading in with a new Climate Change Implementation Plan (CCIP) to meet the challenges that intense weather events pose to our water infrastructure. The WRD announced the plan in fall 2023.

Infrastructure designed and installed in the 20th century is often undersized and/or lacks regular maintenance to adequately handle the realities of the 21st-century climate. The precipitation estimates used to design much of the current stormwater and wastewater infrastructure are based on pre-1992 rainfall data.

In addition to being undersized when it was designed, aging infrastructure often is decades past its intended lifespan. Updating planning efforts to reflect changing climate conditions reduces the risk of negative impacts and protects water resources.

The WRD’s wet-weather regulatory programs currently are required to use information from the National Oceanic and Atmospheric Administration Atlas 14 data server, published in 2013, as the precipitation data source to determine the required volume of rainfall that must be managed, but this decade-old data does not account for Michigan’s rapidly changing climate.

The CCIP, which accounts for some uncertainty when evaluating climate change impacts, recognizes that Michigan already experiences costly impacts from climate-induced weather events, including harm to water quality and infrastructure. The incremental approach of the WRD intends to address the need for additional resiliency planning to prepare infrastructure to handle 21st-century climate change and protect Michigan’s water resources.

As supervisor of WRD’s Stormwater Permits Unit, Christe Alwin oversees permitting for the construction, industrial, and municipal stormwater programs. She says living in urban areas in Lower Michigan and rural areas in the Upper Peninsula has offered a unique opportunity to understand Michigan’s hydrology and the importance of stormwater permitting and management.

Change Factors

The WRD Climate Change Implementation Plan describes requirements and recommendations to increase infrastructure resiliency and minimize the effects of climate-induced weather on Michigan’s water resources, including:

  • Use of the most up-to-date precipitation estimates available to determine the required volume of rainfall that must be managed, known as the “design storm.”
  • Implementation of a 10% “resiliency factor” as part of wet-weather regulatory programs. This will require stormwater and wastewater infrastructure in the Combined Sewer Overflow, Sanitary Sewer Overflow, and Municipal Separate Storm Sewer System (MS4) programs to be designed to manage 10% more volume than the design storm.
  • Recommendations for water quality programs to increase awareness of climate change strategies and evaluate best practices. • Best management practice recommendations for WRD’s Resources Program, which includes dam safety and inland lakes, streams, and wetlands protection.
  • Support for periodic updates of precipitation estimates to account for trends over time and develop adjustment factors using future climate model projections.

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