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Basement Risk Index™ · Community Report

Basement Flood Risk in Holly Township, Michigan

Holly Township’s Basement Risk Index is 23/100 (MODERATE). 24% of homes here were built before 1960 (U.S. Census ACS 2020-2024, updated Jul 2026), the biggest driver of basement-flooding risk in this region.

23BRI / 100
MODERATE RISK
Ranked #76 of 116 metro Detroit communities

Data confidence: C, modeled from housing-age measures; no local flood records integrated yet. How the score is built →

Holly Township, Michigan carries a Basement Risk Index of 23 out of 100, ranking #76 of 116 metro Detroit communities, well below the metro median of 37. Holly Township is one of the metro's newer communities, its housing peaking in the two-thousands, well into the era of modern basement waterproofing, the main reason its Index sits toward the lower end of the range. Among Holly Township and its five nearest neighbors it carries the second-highest modeled risk; its housing is mostly owner-occupied and middle-income for the region.

Water in your basement in Holly Township right now?

  1. Don’t enter standing water if the power is on. Cut it at the breaker only from a dry spot, or call an electrician.
  2. Photograph and video everything before you move or clean up anything, insurance and city claims both turn on this.
  3. Michigan law gives you about 45 days from discovery to file a written damage claim with your sewer authority. Start today.
  4. Once it is safe, call a licensed waterproofing contractor. Do not wait for it to dry on its own.

Holly Township basement risk at a glance

Basement Risk Index23 / 100 (MODERATE)
Metro rank#76 of 116
Homes built before 196024%
Peak building era2000s (20% of homes)
Median year built1985
Median home value$240,800
Median household income$75,276
Owner-occupied80%
Neighborhoods analyzed2

Holly Township's score is modeled from U.S. Census housing data; no municipal flood records are integrated yet. The Basement Risk Index is built from U.S. Census housing data and documented flood records. See our full methodology.

When Holly Township was built

Holly Township's housing is spread across several decades, peaking in the two-thousands at about 20% of today's homes; some of the stock, 24%, predates 1960. These are mid-range homes for the metro, and basements built before the 1960s typically lack the sump pumps, perimeter drain tile, and backwater valves that became standard later, leaving many on their original clay drain tiles.

2020 or later
3%
2010s
9%
2000s
20%
1990s
13%
1980s
10%
1970s
13%
1960s
9%
1950s
7%
1940s
3%
Before 1940
14%

How basement risk varies inside Holly Township

We score 2 individual neighborhoods inside Holly Township, and the pattern is skewed to the lower bands: 0 fall in the high or very high band, 0 are elevated, and 2 are moderate or lower. The number that matters is the one for your own block, not the city average.

0Very High
0High
0Elevated
1Moderate
1Lower

What this means for Holly Township homeowners

Holly Township scores in the moderate band, but moderate is not zero on clay soil. Prevention is cheap relative to a flooded basement, and a free check tells you what you are working with. Among its immediate neighbors, Holly Township scores higher than Rose Township, so the block next door is a better guide than any metro-wide average.

Why Holly Township homes face basement risk

Basement risk in Holly Township comes down to two things: how old its houses are and the clay beneath them. With some of its homes, 24%, built before 1960 and the biggest share going up in the two-thousands, many sit on original clay drain tile, and southeast Michigan's dense clay holds water against those foundations rather than letting it drain.

How Holly Township compares

Holly Township's Index of 23 ranks #76 of 116 communities region-wide and sits below the metro Detroit median of 37. It runs higher than its nearby neighbor Groveland Township.

Does insurance cover it?

Often not. Standard Michigan homeowners policies commonly exclude sewer backup and groundwater unless you carry a specific endorsement. Before the next storm, it is worth reading our guide on whether insurance covers sewer backup in Michigan and checking your declarations page.

What to do about it

  1. Lower risk is not zero risk on the region's clay soil, a free prevention check takes about 30 minutes.
  2. Watch for symptoms after storms; what you see at your own home matters more than any average.
  3. Maintain gutters and grading, the two cheapest protections any Michigan home has.

Hiring in Holly Township?

We keep public-record profiles of metro Detroit basement waterproofing contractors, drawn from their own listings and Michigan licensing records. No ratings and no pay-to-play, just the record. Browse the contractor records →

See Holly Township on the full metro Detroit Basement Risk Index map →

Concerned about this score?

We connect Holly Township homeowners with one licensed, insured basement waterproofing contractor for a free, no-obligation assessment. Your information goes to one local pro, never to lead lists.

Request your free assessment →

See Holly Township on the interactive metro map →
Read the published methodology →
Browse all 116 communities ranked →

Nearby communities

Rose Township · 22Groveland Township · 16Springfield Township · 11Highland Township · 23White Lake Township · 21

Homeowner guides

Does insurance cover sewer backup?What to do when your basement floodsWhat waterproofing costs in metro DetroitHow to choose a waterproofing contractorSump pump costs in MichiganBackwater valves: cost and who needs oneThe 2021 metro Detroit floodsWhat keeps a Michigan basement dry

Frequently asked questions

Where does Holly Township rank for basement-flood risk among nearby communities like Rose Township and Groveland Township?

Holly Township scores 23 out of 100, ranking #76 of 116 metro Detroit communities (MODERATE risk). Among its five nearest neighbors it carries the second-highest risk: Rose Township scores 22 and Groveland Township scores 16.

Are Holly Township's homes older than those in nearby Rose Township and Groveland Township?

24% of Holly Township homes were built before 1960 (median year built 1985, with the largest share in the two-thousands). In Rose Township, 19% predate 1960 (median year built 1982). Older housing means more basements plumbed before sump pumps, weeping tile, and backwater valves were standard.

What is the biggest basement-flood driver in Holly Township versus Groveland Township?

Housing age and clay soil. 24% of Holly Township homes predate 1960, and southeast Michigan's dense clay holds water against older foundations rather than draining it. Holly Township scores 23 and Groveland Township 16, so the same prevention steps apply, sized to each home.