Local government and climate change: Planning for rainfall intensification in the Midwest

The Third National Climate Assessment predicts increased rainfall events and flooding in the Midwest. Communities that plan ahead and adapt to predicted conditions stand to ‘weather the storm’.

Maps show projected changes for the middle of the current century (2041-2070) relative to the end of the last century (1971-2000) across the Midwest under continued emissions. Source: NOAA NCDC / CICS-NC.

Maps show projected changes for the middle of the current century (2041-2070) relative to the end of the last century (1971-2000) across the Midwest under continued emissions. Source: NOAA NCDC / CICS-NC.

On May 6, 2014, the U.S. Global Change Research Program released The Third National Climate Assessment. The report, in its various chapters and versions, details a variety of current and predicted impacts in the United States resulting from a changing climate. Current and predicted impacts presented in the report vary by geographic region and sector (such as health, water and agriculture), and readers may wish to explore particular sections of the report in depth.

Of particular concern to Michigan residents may be the forecasts for increased incidence of large storm events. One of the key messages in the report for the Midwest reads:

Extreme rainfall events and flooding have increased during the last century, and these trends are expected to continue, causing erosion, declining water quality, and negative impacts on transportation, agriculture, human health, and infrastructure.

During the past century, overall annual precipitation has already increased throughout the region (up to 20 percent in some locations). Much of the increase to date has been the result of increased intensity of the heaviest rainfalls.

Unlike light and moderate rain events, intense rainfall ‘flashes’ off impervious surfaces in cities and suburbs, which overwhelms retention basins and storm sewers. Such events can exceed the capacity of combined municipal sewer systems and lead to overflows of sewage into waterways, compromising water quality as a result. In July 2012, the City of Marquette, on the southern shore of Lake Superior, experienced its first beach closures in city history due to high levels of E. coli.

Further, intense rain increases the likelihood of flooding events. While commonplace to plan around the once-in-100-year flood level, increased precipitation is prompting communities in the Midwest like Cedar Falls, Iowa to strictly regulate construction in the once-in-500-year flood level. Flashing stormwater and flooding both contribute to erosion of quality topsoil and threaten property and infrastructure in the path of rising water, sliding mud, or both.

Local governments do have options to mitigate the impacts of increased storm events resulting from climate change. By prohibiting development within wetlands, floodplains and other natural landscapes important for groundwater recharge, communities can maintain ‘green infrastructure’ and save on expansions of traditional gutter and sewer storm water systems. Combined with key land purchases and protections, green infrastructure amounts to a network of natural landscapes that allow for retention of storm water and infiltration into the ground. As a result, less storm water ends up in storm sewers and the potential for overflows is reduced.

Where new development is most appropriate, communities might consider adopting Low Impact Development (LID) regulations that limit the amount of impervious surfaces on development sites and require storm water to be managed on site. Natural buffers along shorelines and planting of trees and other vegetation help to minimize runoff from development sites and limit pollutants and sediment from reaching waterways.

Communities that plan ahead for the impacts from climate change will be more resilient in the future and less likely to be overwhelmed by the physical invasion of intense rainfall and the financial drain from cleaning-up the aftermath of intense storms. The City of Marquette, Michigan worked with Michigan State University Extension to develop a climate adaptation plan. If your community is interested in doing the same, contact an Extension educator on the MSU Climate Outreach Team.