CNT Study on Urban Flooding: Sound Familiar?

A neighbor, Joel Feinstein, forwarded me a case study from the Center for Neighborhood Technology. While reading the report, I spent the entire time thinking, Yes! That’s so true! That’s our problem! But I also found a few surprises.

I invite you to take a look and see if the report reflects your experience.

Today’s Urban Flooding Is Not Your Grandpa’s Flood

The CNT study does a great job of combining information from both public and private sources, collected during a five-year study period (2007 to 2011).

One big conclusion is that the areas hardest hit by flood damage are generally not in traditional river or lake floodplains, as identified by the Federal Emergency Management Agency (FEMA), where coverage from the subsidized National Flood Insurance Program (NFIP) is a requirement for obtaining a mortgage. p 7 Outside these areas, anyone can buy flood insurance, but many who could benefit, do not.

Another point is that Mother Nature is an equal opportunity property wrecker, but flood damage does affect lower-income areas of Cook County at slightly higher rates.

It would be nice to blame the whole problem on the amount of impervious surface area, but–surprise!–paved surface doesn’t correlate exactly with flood damage, since so many other factors are involved.p 7 For example, inadequate drainage systems and aging infrastructure are huge issues.p 2

Finally, in the Midwest, “very heavy precipitation events increased by 31 percent between 1958 and 2007.”p 10 The CNT survey found that, of those who had flood damage, 70 percent had three or more events, and 20 percent had 10 or more events, during the five-year study period.p 6

We have a problem, and without action, it’s just going to get worse.

How Is Wilmette Doing?

cnt feature picI found a few interesting facts for Wilmette.

The data apply to the entire 60091 zip code, and compare Wilmette to other Cook County zip code areas, for the five-year study period (2007-2011).

For Wilmette:

  • Impervious surface area is in the 29 percent to 34 percent range, not the highest in the county.p 11
  • Almost none of Wilmette is in a traditional floodplain, but we were among the top zip codes in terms of claims submitted to NFIP.p 17
  • We were among the top zip codes for private insurance claims.p 16
  • For claims submitted to any public or private source, we were in the next to the top range (470 to 1,860 claims).p 20 This is significant, since many of us don’t even try to submit claims, and there are only a total of 9,742 households in Wilmette.
  • We were among the top zip codes for payouts.p 22

Damaged Health, Finances, and Property

In general, flooding has an impact beyond the initially reported data for an event:

  • Wet basements decrease property values by an estimated 10-25 percent.p 1
  • Almost 40 percent of small businesses fail to reopen after a flooding disaster.p 1
  • Many property owners don’t have insurance, don’t make claims, or receive inadequate payouts, making damage hard to manage, and true costs hard to gauge.p 4

The next two tables summarize the average impact on Cook County residents:

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Average property damage is $7,769. Total five-year payout for the county was $773 million. Source: CNT, The Prevalence and Cost of Urban Flooding p 8, 10.

Most Residents Take Action, But Only A Few Resolve Problems

I’ve found that many Wilmette friends and neighbors have tried to flood proof their property in one way or another, but many are confused about what works best, and only one sounded confident her problems were solved (and she’s not in the most flood prone area).

The next tables confirm Wilmette’s experience.

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Most homeowners try to fix their problems, but only 6 percent report resolution. Source: CNT, The Prevalence and Cost of Urban Flooding p 9.

Recommendations to Make Progress

The CNT study argues that better research and data are required to figure out the best solutions. And individuals cannot solve flooding alone.p 10

Solutions for individual homeowner must be combined with solutions for communities. Flood proofing, upgrading drainage systems, practicing green building practices, and creating green infrastructure are all required to prevent flood damage.

Here’s a recommendation that seems important as a way forward:

Government should strengthen programs that encourage or require developers and property owners to reduce impervious surface area, and retain and manage stormwater run-off on the property. The use of impervious surface fee-based budgeting (known as ‘Rain Funds’),8 the adoption of ordinances that require new development or redevelopment to have on-site retention measures, and the use of State Revolving Funds for green infrastructure are good examples.

Source: CNT, The Prevalence and Cost of Urban Flooding p 10.


If you’re short on time, but curious how we compare with our neighbors, check out this copy of the report that I’ve marked up to highlight Wilmette data.

For more information on what individual homeowners and concerned citizens can do, visit Center for Neighborhood Technology and RainReady, the site CNT supports to focus on flooding issues.

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