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Think you’re not in a flood zone? Maybe think again

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A comprehensive new assessment of flood risk, released this week by the nonprofit First Street Foundation, exposes blind spots in FEMA’s maps to show just how vulnerable the nation’s properties are. Built by researchers from private companies and universities, the model calculates the cumulative risk for every property in the contiguous United States from rainfall, storm surge, tidal and river flooding. FEMA says 8.7 million properties are in areas susceptible to a “hundred-year flood” — a flooding event with a 1% chance of occurring in a given year. The new data says there are 14.6 million properties at risk. […]

In Cook County, where Chicago and its suburbs are located, the new model found more than 150,000 properties are at high risk — about six times as many as FEMA’s estimate. […]

Illinois has warmed about 1.2 degrees and experienced 10% to 15% more precipitation over the last century, according to the Illinois State Climatologist’s office. But the rainfall is not uniform — it’s increasingly coming down in bunches. In the Great Lakes region, the most powerful storms have increased 35% between 1951 and 2017.

Last year, state scientists updated the standard for new construction requiring state permits, including the design of storm sewers, retention ponds and road drainage, to accommodate increasing precipitation trends.

Because state and local officials use FEMA maps to help guide and justify their planning decisions, they tend to focus almost exclusively on the areas the agency has deemed high risk.

For example, the Metropolitan Water Reclamation District of Greater Chicago has spent around $22.2 million helping municipalities acquire 90 flood-prone properties, raze the structures on those properties and keep those areas as open space. The agency has designated additional high-risk zones beyond the FEMA maps, but so far, the properties purchased throughout Cook County have been located in FEMA’s high-risk zones. […]

In Illinois alone, there has been more than $2.3 billion in documented property damage from flooding in urban areas between 2007 and 2014, according to a study led by the Department of Natural Resources. Over 90% of those insurance and disaster assistance claims were for properties outside of the FEMA floodplain — where residents weren’t required to buy flood insurance and may not have been alerted to the risk when they bought their homes.

If anything, the First Street model still underestimates risk in some properties, because its analysis is based on ground-level flooding, as are the FEMA maps. Andrew Smith, chief operations officer at Fathom, said basements can flood more frequently than the model suggests. […]

Between 2007 and 2016, there were nearly 230,000 flood-related claims in Chicago resulting in $433 million in payouts, according to a 2018 report from the Center for Neighborhood Technology. Of those, 87% of paid flood claims were located in communities of color.

Click here to visit the website and tell us what you found.

posted by Rich Miller
Wednesday, Jul 1, 20 @ 1:01 pm

Comments

An old house we lived in is a 1/10 for flood threat.

11 or so years ago we had 6.4 inches of rain in about an hour and 15 minutes - it turned our street into a white water rapid and inundated every home down the block from us. That rain also killed woman walking through a flooded underpass in Springfield.

Not sure how they judge flood risk - but intense storms with four and five inches of rain in an hour are becoming way more common and it would seem there is very little you could do about that.

Comment by Cool Papa Bell Wednesday, Jul 1, 20 @ 1:30 pm
I have a 1/10 flood risk, but I think several of my neighbors would be quite surprised.

Comment by Candy Dogood Wednesday, Jul 1, 20 @ 1:31 pm
===11 or so years ago we had 6.4 inches of rain in about an hour and 15 minutes===

This was when I started paying attention to how old Springfield’s rain water run off system was and realized how many areas of the city rely on ditches.

Comment by Candy Dogood Wednesday, Jul 1, 20 @ 1:35 pm
Still not . Warmer and wetter also means the prairie state can never be the prairies state again.

Comment by Not a Billionaire Wednesday, Jul 1, 20 @ 1:45 pm
I’m one in ten, too. Similar to another risk level I had calculated off the FEMA website. Said risk was low for the next 30 years. I’ve never had any flooding problems and I’ve lived at the same location for more than 25 years.

Comment by Rachel Wednesday, Jul 1, 20 @ 1:59 pm
Western Union county and Alexander county have been flood zones forever. The last couple decades have only made it more evident.
One can drive down the “snake road” in Pine Hills and look on the bluff faces where the Mississippi used to run. It’s roughly two miles from where the banks are now.
Unfortunately there are a number of residents in those areas who refuse to accept it.
Many were offered buyouts by FEMA in the early 90’s but declined, and were told that this opportunity wouldn’t come again.
Most can’t get any flood coverage now. How some get loans is beyond me.

Comment by efudd Wednesday, Jul 1, 20 @ 2:06 pm
Illinois: The Swamp-ish State

Comment by New name legislation Wednesday, Jul 1, 20 @ 2:11 pm
I have very little risk, but I’m on a tiny bit of higher ground, probably as close to a ridge as you can find on the north side of Chicago.

Comment by Cheryl44 Wednesday, Jul 1, 20 @ 2:27 pm
Politics is a hobby for me, flood risk assessment is part of my vocation (something I have been working on for 35 years).

This is a really great advance for several reasons: 1) It projects the risk in areas not covered by FEMA flood hazard maps (including small streams and “pluvial” flooding). 2) The methodology attempts to address a consistent problem with forecasting: the heavy reliance on statistical analyses of the historical record of flooding. With climate and land use changing, this has been a big challenge.

My initial observations (based on places with which I am the most familiar): It does a nice job on low areas and small streams not covered by the FEMA maps; although, it misses some of the frequently-flooded low areas (very shallow “kettle hole” depressions) in northern Illinois’ glaciated area. It also underestimates the frequency/depth of flooding experienced along the upper Illinois River in the most recent 10-20 years. My final critique is that the coastal flooding model methodology does not appear to include lakefront flood hazards, only marine coasts.

I’ll be playing with this all summer…

Comment by Pot calling kettle Wednesday, Jul 1, 20 @ 2:33 pm
I have lived through many many 100 year floods even a 500 year flood. I backed up to a park and saw Chuck Percy in a row boot from my back yard. Finally my office was taken on flood projects. All this was in Addison. The flood maps were generally wrong and flood zones changed without notice so people that lived there never knew their house was in flood zone.Most of it was caused by building in flood areas. I would flood three days after a rain as all the water worked its way down from Woodfield along Salt Creek. Fortunately if was finally fixed. But in a bad storm in still wake up nights wondering what is going to flood.

Comment by DuPage Saint Wednesday, Jul 1, 20 @ 2:33 pm
Welcome to my world. I spent most of my career in DuPage County. Back in the 90’s we all realized that the 70’s era flood insurance rate maps (FIRMs) we were using were woefully out of date. The County entered into an agreement with FEMA and updated the modeling and issued new maps in the mid 2000’s. Fortunately, the agreement allows DuPage to also update the maps. Cook hasn’t gotten there yet. MWRD had been exclusively focused on the TARP (rightfully so) that they never were able to think about watershed planning until the last decade. The first plans bear 2010 dates. As noted by Ms. Song, these plans must have the dynamic ability to adjust as does DuPage to make any substantive progress. A cursory reading leads me to believe that they are but, they started behind the 8-ball so they have a lot of catching up to do.

Comment by Proud Sucker Wednesday, Jul 1, 20 @ 2:41 pm
Another very nice aspect is the language used to characterize the flood hazard. The traditional 100- and 500-year desigantions were misleading to most people; this model bases risk on a percent chance of being flooded to a given depth over a period of time. The end result is much more meaningful and useful to the average person.

Comment by Pot calling kettle Wednesday, Jul 1, 20 @ 2:52 pm
Excellent resource and spot on for our area. Maybe someone should let IL Agriculture, EPA, IDOT, and Public Health in on this. We that live here already knew this, but they refused to listen.

Comment by It's not me Wednesday, Jul 1, 20 @ 2:54 pm
This is flood zone data for the 62561 area:
Approx. 207 properties have a 0.2% chance
tooltip of some amount of water reaching their building in 2020. Tap/hover for more information.

I thought it would be higher since I only live 1/2 mile from the Sangamon River.

Comment by Mama Wednesday, Jul 1, 20 @ 3:26 pm
I’m listed as a 1/10.

But a couple years back, we were the only home on the block that didn’t have water in the basement, so I’m still glad we got a new generator.

– MrJM

Comment by @misterjayem Wednesday, Jul 1, 20 @ 3:35 pm
I question the results of the flood factor study.

Using the National Weather Service “Advanced Hydrologic Prediction Service”, the inundation mapping tool shows that the Illinois River level would have to be more than 7 feet above the record flood elevation before my house gets close to being flooded.

The flood factor study is claiming my house has a 9% chance at least once in the next 30 years. With the flood depth to be up to 2.9 feet.

If the flood factor study is correct, my town will be under water long before my house is flooded.

Comment by Huh? Wednesday, Jul 1, 20 @ 3:41 pm
This is really concerning for an additional reason: the FEMA run National Flood Insurance Program is a big mess. Deep in the red with no relief in sight, Congress set a rate increase schedule that can amount to flood insurance costing more than a mortgage. This has rendered some properties worthless and has a greater impact on lower value properties. It’s a looming financial problem that needs to be addressed by Congress though I worry it won’t be until many more people have suffered. Also, FWIW, Senator Rezin has been a great state leader on this and one of the best state agencies in the state (IMHO) is the Illinois Office of Water Resources/Statewide Floodplain Program.

Comment by Gideon Wednesday, Jul 1, 20 @ 3:42 pm
I’m listed as 1/10 low risk…Luckily, I live on a high spot.

Comment by Dotnonymous Wednesday, Jul 1, 20 @ 3:48 pm
I’m listed as 1/10 But they recommend I have flood insurance? I live 2 miles from the Illinois River and 46′ above the river level. When the river goes up 46′, the river will be wider than the Mississippi.

Comment by Bruce (no not him) Wednesday, Jul 1, 20 @ 3:56 pm
Like another commenter, the properties I’m involved with are rated 1/10 minimal, but the site recommends flood insurance. That reads a bit like a CYA effort because frankly, if these properties ever flood, I’ll look to hitch a ride on an ark.

Comment by Flapdoodle Wednesday, Jul 1, 20 @ 4:22 pm
== I live 2 miles from the Illinois River and 46′ above the river level.==

Not all flooding is from a river leaving its banks; that is one of the weaknesses of the FEMA maps.

This site http://illinoisfloodmaps.org/twi.aspx shows areas at risk after heavy rainfall. It is much more sensitive to this type of flooding than the floodfactor site (perhaps a bit too sensitive in some places).

If someone is concerned about what any flood hazard map shows, it is a good idea to find someone familiar with flood hazard assessment (usually a geologist or an engineer) and ask for their advice. These maps are very useful, but because accuracy can vary quite a bit.

Two other useful sites for flood maps:
http://illinoisfloodmaps.org
https://msc.fema.gov

Comment by Pot calling kettle Wednesday, Jul 1, 20 @ 4:37 pm
Hhhmmm, tell my 1 in 10 chance basement its 3 in 5 year record is not acceptable. Thanks for the additional resources, PCK.

Comment by Need A Suggestion Wednesday, Jul 1, 20 @ 4:54 pm
Based on what I see for my area, west of Springfield airport, I wouldn’t trust this model. It seems to neglect we’re on high ground and our lake would overflow before the water could come anywhere near the houses.

Comment by FormerGOPer Wednesday, Jul 1, 20 @ 7:10 pm
City of Rock Falls, oh my

Comment by 100 miles west Wednesday, Jul 1, 20 @ 8:27 pm
I own a home in an area known to be flood-prone, but it has never sustained above-ground flood damage, even in the most severe floods years before I bought it. It was never in FEMA-designated floodplain for insurance purposes, only for local regulatory purposes. The unfinished basement has occasionally taken on water, but not since 2013.

Last year, my property was drawn out of all flood plains due to the completion of a long-term flood prevention project upstream. I bought flood insurance last November, and I will carry it for the rest of my time in this house.

The First Street site has me at 6/10.

Comment by Tim Wednesday, Jul 1, 20 @ 9:31 pm