Flood 2014

THE GREAT FLOOD OF 2014 Residents of Metropolitan Detroit won’t forget August 11, 2014 for a long time. Over four and a half inches of rain fell that day, the second highest 24 hour rainfall ever recorded in southeast Michigan.

The rain overwhelmed the area’s storm water infrastructure, resulting in serious flooding in Detroit and dozens of suburban communities. President Obama designated metro Detroit a major federal disaster area. Flood damages are estimated at close to one billion dollars. (http:// www.crainsdetroit.com/article/20140824/NEWS/308249964/how-southeast-michigan-couldstem-the-tide-when-the-next-storm-hits) Some areas were particularly hard hit. Many communities just north of Detroit in Southeast Oakland County and Southwest Macomb County, had rain in amounts ranging from just under 5 inches to over 6 inches in just six hours. Hundreds of streets and Type to enter text basements were flooded.

The 14 communities in Southeast Oakland County are older suburbs served by combined sewer systems that collect sanitary and surface run off. In dry weather the combined sewage flows south into the Detroit Water and Sewer Department (DWSD) system for eventual treatment and discharge into the Detroit River.

Ty In wet weather its more complicated. When DWSD system capacity is exceeded flows are diverted into the George W. Kuhn Retention Treatment Basin (GWK). (https://www.oakgov.com/ water/Documents/gwk_brochure_jacy_garrison_20091223.pdf) The GWK is a massive, 60 foot diameter, 2.2 mile long underground tunnel extending northeasterly from the City of Royal Oak in Oakland County to the City of Warren in neighboring Macomb County. Flows diverted to the GWK obtain primary treatment and are discharged back to DWSD unless the capacity of the GWK is exceeded. When that happens the facility discharges the excess flow to the Red Run Drain, which flows into the Clinton River and then into Lake St. Clair, about 10 miles away.

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The GWK has a storage capacity of 124 million gallons. It is designed to handle a 10 year 1 hour storm. The National Weather Service calculated that the storm that hit the 14 communities in the GWK drainage district was a 332 year 1 hour storm, a deluge that completely overwhelmed the facility. In the two days after the storm the GWK discharged over 2 billion

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gallons of partially treated sewage into the Red Run, well over twice what it would typically discharge in a year.

Storms like the August 11 deluge are likely to become more common. According to the National Oceanographic and Atmospheric Agency (NOAA) the climate in the Great Lakes region is warming. Average precipitation is increasing. Southeast Michigan has seen close to a 12% increase in total annual precipitation from the 1961-1990 average to the 1981-2010 average.

Most climate models project that observed increases in total annual precipitation for the Midwest will continue.

Severe storms are becoming more frequent in the region, and the amount of precipitation during those storms is increasing. In Southeast Michigan, the annual number of extreme 7-day precipitation events has increased since the 1930s, and heavy rains are twice as frequent now than a century ago. The Midwest saw a 37% increase in the amount of rain falling in the

heaviest 1% of precipitation events from 1958 to 2007. (http://glisa.umich.edu/media/files/ projects/DCAC/DCAC_Climate_Impacts.pdf) These are worrisome developments for the GWK drainage district. While 60-70 per cent of the area sewer system was built before 1970 (http://www.freep.com/story/news/local/michigan/ 2014/10/26/august-storm-dumped-billions-gallons-sewage/17907335/) the GWK is relatively new, having been completed in 2006 at a cost of 132 million dollars.

Further expansions would probably require widening the existing easement, which extends through thoroughly built-out areas and would likely be prohibitively expensive.

Alternatives must be considered. There are a few opportunities for natural storm water retention in the district. For example, the City of Royal Oak closed a municipal golf course and plans to convert the open space to a combination of athletic fields and natural area.

Real opportunities lie downstream of the GWK district. Large areas of the City of Detroit are depopulated and empty. Detroit is considering utilizing some of these areas for “blue infrastructure” such as ponds and wetlands. (http://detroitfuturecity.com/wp-content/uploads/ 2014/12/DFC_CitySystems_2nd.pdf.) Communities connected to the DWSD could collaborate on a plan to develop green infrastructure in proportion to their contributions to stormwater flows.

The streets, yards, and basements in the 14 communities are likely to become permanent parts of the stormwater infrastructure unless creative solutions are found. These communities must begin preparing for a wetter future now.