Quad Cities Flood History: What It Means for Your Basement
The Mississippi set a new record here in 2019. Our heaviest rains keep getting heavier. Here is what the river and rain records actually say, and what they mean for the basement under your house.
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The Quad Cities and water
How high our rivers have gone
Each bar shows how far the record crest went above flood stage at that gauge.
2019 was the big one. The Mississippi crested at 22.70 feet at Rock Island on May 2, 2019, just above the 1993 record of 22.63 feet. Two days earlier, on April 30, temporary flood barriers failed and water poured into downtown Davenport. The river stayed in flood for a record 51 days.
The Rock River has its own history. At Moline it set a record of 16.53 feet in April 2013, and at Joslin it reached 18.51 feet again in 2019.
Our heaviest rains are getting heavier
The Quad Cities averages a little over 38 inches of precipitation a year. But averages hide the storms that actually flood basements. Across the Midwest, the amount of rain falling in the heaviest 1% of storms rose 42% from 1958 to 2016, according to the Fourth National Climate Assessment.
Wet stretches add up too. In May 2019 the Quad Cities had 22 rainy days in a row, breaking a record from 1933, and logged close to nine inches of rain for the month.
That matters because a basement rarely leaks from one shower. It leaks when the ground is already soaked and another downpour has nowhere to go.
River floods and wet basements are not the same thing
Here is the honest part. If the river itself comes over the bank and into your yard, no waterproofing system will keep it out. That is overland flooding, and it is a job for levees, flood walls and flood insurance.
Most wet basements in the Quad Cities have nothing to do with the river reaching the house. They come from rain and groundwater. When the soil around your foundation fills with water, it pushes on the walls and floor. That is called hydrostatic pressure, and it forces water through cracks, the joint where the wall meets the floor, and old window wells.
Homes in low areas near the Mississippi, Rock and Wapsi can also see groundwater rise when the rivers run high for weeks, like in 2019. That is when a reliable sump pump earns its keep. If you live in one of the river towns we serve, see our pages for Davenport, Bettendorf, Moline, Rock Island, East Moline, LeClaire and DeWitt.
A basement flood checklist
Most of these cost little or nothing, and fall is a good time to do them before the spring rains.
- ✓Clean gutters and make sure downspouts carry water at least several feet from the house. Lawn and yard drainage
- ✓Check that the ground slopes away from your foundation on every side. Fix the drainage first
- ✓Pour a bucket of water in your sump pit and make sure the pump kicks on and the discharge line is clear. Sump pump maintenance
- ✓If the power goes out in a storm, your pump stops. A battery backup sump pump keeps it running.
- ✓Clear leaves and dirt out of window wells and make sure they drain. Window well drainage
- ✓Look for new cracks, damp spots or white powder on the walls. See the warning signs
- ✓If your basement is finished, know what you would lose. Protecting a finished basement
Worried about your basement this spring?
We look at where your water is actually coming from and fix only what your home needs. Behncke has worked on Quad Cities basements since 1948.
Sources: National Weather Service river gauge records; Davenport Public Library, Special Collections (2019 flood); Wikipedia, Mississippi River floods of 2019; NOAA 1991 to 2020 climate normals (Moline); Fourth National Climate Assessment, Vol. I (Easterling et al., 2017); WQAD (May 2019 rain record).