Houston's Draft Flood Maps Catch 42% of Harvey's Worst-Hit Homes Outside the Floodplain

Houston's Draft Flood Maps Catch 42% of Harvey's Worst-Hit Homes Outside the Floodplain

Houston's new flood maps are supposed to fix a problem Harvey made famous: homes that flooded far from any mapped floodplain. We checked how well they do. Of the 3,799 Harris County homes with major damage or worse in FEMA's Harvey model that sit outside today's 100-year floodplain, the MAAPnext draft maps put 1,613—42%—in a high-risk zone.

For damaged homes overall, the draft catches far fewer. 64% of the 52,848 single-family homes FEMA modeled as damaged sit outside today's high-risk zone, and the draft maps move 8,952 of them, or 26%, into one. That leaves 25,104 Harvey-damaged homes outside the high-risk zone on both maps.

Key Findings

• 42% of the worst-hit homes outside today's floodplain are high-risk on the draft, against 26% of all damaged homes outside it.
• 25,104 Harvey-damaged homes stay outside the high-risk zone on the draft maps.
• 2,700 damaged homes in today's high-risk zone fall outside it on the draft.
• The catch rate swings by ZIP code, from nearly all of Kingwood's worst-hit homes to almost none in parts of Spring.

Where Harvey's Damaged Homes Land on Both Maps

Shaded Zone X, FEMA's 500-year floodplain, is where the draft does most of its work: it moves 43% of the damaged homes there into the high-risk zone. In unshaded Zone X—the "minimal hazard" area that held about as much Harvey damage as the floodplain itself—it moves 12%.

Major Damage Is Where the Draft Catches the Most

FEMA's model rates damage by how deep the water got at each home, and the draft's high-risk zones are drawn where deep water is likely. So the catch rate climbs from 22% for "affected" homes to 51% for major damage. Shallow flooding is often rain that couldn't drain fast enough, which the draft maps separately as "community flooding" rather than as a high-risk zone.

Destroyed homes break the pattern, at 18%. Of Harris County's 973 destroyed homes outside today's floodplain, 729 are in just two ZIP codes. Those are the Energy Corridor's 77079 and Spring's 77373, where the draft catches few of them.

ZIP Codes With the Most Damaged Homes Outside the Floodplain

For every ZIP code, download the full table (CSV).

Where the draft catches up. In Kingwood's 77345, the draft maps put 337 of the 357 worst-hit homes outside today's floodplain into a high-risk zone. More on the area in our Kingwood flood risk guide.

Where it doesn't. In the Energy Corridor's 77079, the draft catches 260 of 1,259. Much of the Harvey flooding there came from the Addicks and Barker reservoirs, which held water behind the dams and released it down Buffalo Bayou. We covered the reservoirs in the Addicks and Barker case.

In Spring's 77373, the draft catches 1 of 300.

The Draft Moves Some Damaged Homes Out, Too

The new maps aren't only bigger. Of the 18,616 Harvey-damaged homes in today's 100-year floodplain, 2,700—15%—sit outside the high-risk zones on the draft. The draft is built on newer ground elevation data and counts flood-control projects finished since the old maps, so some homes move out, and the lines can still shift before the maps are final. A home that flooded in Harvey is worth insuring whatever either map says.

What It Means for Houston Homeowners

1. Check both maps. A FloodMaps report shows your FEMA zone today and your draft MAAPnext zone free. Two minutes, no signup for the free check.
2. Don't read "outside the high-risk zone" as "safe." Most Harvey-damaged homes were outside today's floodplain, and most of those stay outside it on the draft.
3. Price a policy before the maps change. The draft maps are currently expected to take effect around 2028. Our MAAPnext update tracks the timeline.

See y'all on the high ground.

Methodology

• Damage. We started with FEMA's modeled building damage for Hurricane Harvey in Harris County, as merged with Harris Central Appraisal District (HCAD) accounts by an open public project. FEMA's model estimates how deep the water got at each building and assigns a damage level: affected, minor, major, or destroyed.
• Homes. We kept single-family homes that FloodMaps has scored, matched on the HCAD account. Where FEMA modeled more than one building on an account, the home counts once, at its worst damage level. That leaves 52,848 homes.
• Today's zone. Each home's zone on the current effective FEMA flood map, read on October 13, 2026. The high-risk zone, or 100-year floodplain, is FEMA's Special Flood Hazard Area (zones A, AE, AO, and VE, including floodways). Shaded Zone X is the 500-year floodplain, and every other Zone X home counts as unshaded.
• The draft. "High-risk on the draft" means the home sits in a high-risk or floodway zone on the Harris County Flood Control District's MAAPnext draft maps, read at the house.
• Counting. We counted homes by HCAD site ZIP code, damage level, today's zone, and draft zone, and every figure above is a sum of those counts. The ZIP table and the CSV use the same counts.

What the data can't tell you:

• FEMA's model undercounts. It places water in about a third as many single-family homes as the Harris County Flood Control District counted flooded, so read every count as a floor.
• Today's map isn't the 2017 map. Harris County's maps were last comprehensively redrawn in 2007 and have been amended since, so a few homes may have changed zones after Harvey.
• MAAPnext is a draft. It's in public review, not a regulatory map, and its zones can change before FEMA adopts them.
• Community flooding isn't separated. The draft maps street ponding as "community flooding," which isn't a high-risk zone, and our copy of the draft doesn't break it out. Some homes counted as staying outside may carry that flag.

Press Note

FloodMaps matched FEMA's modeled Harvey damage for 52,848 Harris County single-family homes against today's FEMA flood map and Harris County's MAAPnext draft maps. Three numbers:

• 64% of Harvey-damaged homes sit outside today's 100-year floodplain.
• 42% of the worst-hit homes outside it are high-risk on the draft maps, against 26% of all damaged homes outside it.
• 25,104 Harvey-damaged homes stay outside the high-risk zone on both maps.

"Harvey showed that the flood map and the flood aren't the same thing," said Ian Smith, founder of FloodMaps. "Most of the homes it damaged were outside the high-risk zone. The new maps fix part of that, not all of it. Anyone in Houston can now check both maps for their own address in two minutes and decide about flood insurance with the full picture."

Data: ZIP code table (CSV). Media questions: contact FloodMaps.

Quick Answers

Did Harvey flood homes outside Houston's floodplain? Yes. 64% of the 52,848 Harris County single-family homes in FEMA's modeled Harvey damage sit outside today's 100-year floodplain.

Do Houston's new flood maps cover the homes Harvey flooded? Partly. The MAAPnext draft maps put 26% of the damaged homes outside today's floodplain in a high-risk zone, and 42% of those with major damage or worse.

Can a home leave the high-risk zone on the new maps? Yes. 2,700 Harvey-damaged homes in today's 100-year floodplain sit outside the high-risk zones on the draft maps.

Are the MAAPnext maps final? No. They're a draft in public review, currently expected to take effect around 2028.

Sources: FEMA modeled Harvey damage merged with HCAD; FEMA National Flood Hazard Layer; Harris County Flood Control District MAAPnext; FloodMaps analysis of HCAD single-family homes.