Over the weekend of June 25 and 26, 2021, most of metro Detroit took 3 to 6 inches of rain in a matter of hours, and a band along the I-94 corridor took far more: the National Weather Service logged about 8 inches in Grosse Pointe Park (NWS Detroit). I-94 and I-696 filled and cars were abandoned in the water, but the lasting damage was underground. The regional sewer system was overwhelmed, and the weekend became federal disaster declaration DR-4607-MI, covering Wayne, Oakland, Macomb, and Washtenaw counties.
What the records show
The claim count is the part that lasted. The Great Lakes Water Authority received roughly 24,000 damage claims from the two June 2021 storms, and in 2022 it denied all of them, citing an engineering review that found no negligence on its part (Crain's Detroit Business). That is why the 2021 flood still shapes how we read basement risk here. The water came and went in a weekend, but the record of which streets took it, and how little the legal system gave back, is permanent. Those reports are part of the more than 13,900 water-in-basement records behind the Basement Risk Index.
Why it was so bad
The rain was not the whole story. Four things about the ground and the pipes under metro Detroit decided whose basement filled:
- Aging combined sewers. Much of metro Detroit's older core uses combined systems that carry both stormwater and sewage in the same pipes. When rain overwhelms them, the mix backs up into the lowest point it can reach, which is a basement floor drain.
- Pump station strain. Reports after the storm pointed to pump stations that could not keep pace with the volume, compounding the backups.
- Clay soil. The dense clay that blankets the region drains slowly, so saturated ground pushes water against foundations rather than letting it percolate away.
- Old housing stock. Across the hardest-hit communities, a large share of homes predate the 1960s, built before sump pumps and backwater valves were standard.
Which areas were hit hardest
The damage concentrated in the older, lower-lying parts of the metro: Detroit's east side, Dearborn and Dearborn Heights, the Grosse Pointes, and Downriver communities. These are, not coincidentally, many of the same communities that rank highest on the Basement Risk Index today. The 2021 event is part of why housing age and sewer era are such strong predictors of basement risk.
What every homeowner can take from it
The pipes and the clay did not change after 2021. Neither did the houses. A home that took water that weekend will take water in the next storm of that size unless its owner made one of these three changes:
- A backwater valve to stop sewer backup, especially in pre-1970s homes on combined sewers.
- A working sump pump with a battery backup, because the power often fails in the same storms that cause flooding.
- Improved exterior drainage and grading to move surface water away from the foundation.
If the next one hits your basement, the clock starts immediately
The 2021 claims left a hard procedural lesson: the deadline is short, and it does not wait for cleanup. Under Michigan law (MCL 691.1419), a claim against a public sewer agency generally requires written notice within 45 days of discovering the damage, and, as 2021 showed, filing on time is no guarantee of payment. If it happens to you, our first-hour guide covers the safety and documentation steps that protect a claim, and our DWSD and GLWA claim walkthrough covers exactly what that written notice must say and where it goes.
Sources reviewed
Primary sources checked September 2026:
- National Weather Service, Detroit/Pontiac, June 2021 flooding summary, the rainfall totals across metro Detroit.
- FEMA, Michigan Severe Storms and Flooding (DR-4607-MI), the federal disaster declaration and the counties it covered.
- Crain's Detroit Business, the roughly 24,000 GLWA damage claims and their denial.
- Michigan Legislature, MCL 691.1419, the 45-day written-notice deadline for a municipal sewer claim.