Every home in Houston is in a flood zone. The question is which one, what it means, and what the seller, the map and the insurer will each tell you if you ask. In Hurricane Harvey, 154,170 homes flooded in Harris County and 68 percent of them were outside the 100-year floodplain, which is why a zone letter is the beginning of the answer and not the end of it. This guide explains how to read a FEMA zone for a specific address, what the Addicks and Barker reservoir flood pools are and why they reach into subdivisions that look nothing like a floodplain, what Texas law requires a seller to disclose, when flood insurance is required and why you should quote it anyway, and how to buy well in a market that has learned all of this the hard way.

It is written by Energy Realty, an independent brokerage whose Energy Corridor office sits between the two reservoirs and Buffalo Bayou, and whose Katy office sits in the reservoirs’ upstream watershed. We do not tell clients that a neighborhood “doesn’t flood.” We show them the map, the disclosure and the quote, and this is that conversation in writing. Every figure carries its source and date.

Step one: read the map, and understand what a zone is

The federal Flood Insurance Rate Map, or FIRM, divides land into zones by the statistical chance of flooding in a given year. FEMA defines the Special Flood Hazard Area as “the area that will be inundated by the flood event having a 1-percent chance of being equaled or exceeded in any given year,” which it also calls the base flood or 100-year flood. Those areas carry the labels A, AE, AO, AH, A99, AR, V and VE among others. FEMA defines the moderate flood hazard area, shaded Zone X, as “the areas between the limits of the base flood and the 0.2-percent-annual-chance (or 500-year) flood,” and the minimal flood hazard area, unshaded Zone X, as “the areas outside the SFHA and higher than the elevation of the 0.2-percent-annual-chance flood.”

Two tools give you the zone. FEMA’s Flood Map Service Center shows the effective FIRM for any address. The Harris County Flood Control District’s Flood Education Mapping Tool overlays the county’s own data and is the better starting point for a Harris County address; Fort Bend County publishes its own. Use both, because the answer is “which zone, on which map, as of which date,” and the date matters, as the section on the new maps explains.

Then understand what the zone is not. It is a probability band drawn from a model, not a record of what happened on that street. The Harris County Flood Control District’s own report on Harvey makes the point with its own numbers: of the 154,170 homes that flooded in the county, 48,850 were within the 100-year floodplain, 34,970 within the 500-year floodplain, and 70,370 outside both. “Of the 154,170 homes flooded, 105,340 or 68% were outside the 1% (100-yr) floodplain,” the district writes, and it attributes that to rainfall that exceeded the design levels of the floodplains and to “intense short duration rainfall rates” that overwhelmed local drainage. A zone tells you the regulatory and insurance consequences. It does not tell you whether the street drains.

One more piece of arithmetic that the label hides. The Harris County Flood Control District’s mapping tool states it directly: structures in the 1 percent floodplain “have a minimum of a 1 percent chance of flooding in any given year and a minimum of a 26 percent chance of flooding during a 30-year period of time.” A 100-year flood is not something that happens once a century. It is a one-in-four proposition over the life of a mortgage, and that is the minimum.

Sources: FEMA, flood zone definitions (fema.gov/glossary/flood-zones); FEMA Flood Map Service Center (msc.fema.gov); Harris County Flood Control District, Flood Education Mapping Tool; Harris County Flood Control District, Immediate Flood Report, Hurricane Harvey 2017 (final). Retrieved August 24, 2026.

Step two: the reservoirs, and the flood pool that reaches into the suburbs

West Houston has a flood feature that exists almost nowhere else in American residential real estate, and it is the reason this guide has a section that most flood guides do not. Two federally owned reservoirs, Addicks north of Interstate 10 and Barker south of it, sit at the western edge of the Energy Corridor. The Texas Water Development Board describes them as owned by the U.S. Government and operated by the U.S. Army Corps of Engineers, built to prevent downstream flooding of Buffalo Bayou in the City of Houston, and normally dry: they “fill with water when it rains to prevent or reduce downstream flooding.” Barker’s dam was built between February 1942 and February 1945; Addicks between May 1946 and December 1948. George Bush Park, 7,800 acres of ballfields and trails, sits inside Barker. On an ordinary day the reservoirs are parkland.

The numbers describe how much water they are designed to hold. Addicks covers 16,780 acres at its emergency spillway elevation of 108.9 feet above mean sea level, with a maximum storage capacity of 204,500 acre-feet. Barker covers about 17,225 acres at maximum pool with 207,000 acre-feet, its elevations published in NAVD88, and the two together hold about 410,000 acre-feet. Those acreages are larger than the land the government owns.

That is the fact that matters. When the Corps planned the dams it considered buying all the upstream land that would be inundated at maximum pool, and did not. According to the stipulated facts in the 2019 federal trial, the government acquired all land at and below an elevation of about 103 feet behind Addicks, roughly 12,460 acres, and at and below about 95 feet behind Barker. The maximum pools sit well above those lines. The Court of Federal Claims later found, in the words of the Federal Circuit’s 2025 summary, that “the Corps was aware or should have been aware since the initial construction of the dams and at every point onward, that the flood pools in the Addicks and Barker Reservoirs would at some point (and thereafter) exceed the government-owned land, inundating private properties.” Subdivisions were built on that private land over the following decades.

Hurricane Harvey was the point at which it happened. As the Court of Federal Claims later recorded from the parties’ stipulated facts, the reservoir water elevations far exceeded the extent of government-owned land in both Addicks and Barker, the first time that had happened since the dams were built. The pools peaked on August 30, 2017 at about 109.1 feet in Addicks and 101.6 feet in Barker, in the Corps’ project datum. Upstream, the reservoir water “could not be contained on government-owned land and flooded onto privately-owned land within the reservoirs.” Downstream, the Corps’ emergency releases and the releases that followed to empty the reservoirs drove Buffalo Bayou through the Memorial area to record levels at every bridge crossing.

The litigation is worth knowing because it shapes the disclosure conversation. On December 17, 2019, Senior Judge Charles Lettow of the U.S. Court of Federal Claims found the government liable for “taking permanent natural-disaster flowage easements across Plaintiffs’ properties” upstream of the dams. On December 22, 2025 the U.S. Court of Appeals for the Federal Circuit, in Ablan v. United States, affirmed the liability ruling and the class certification, affirmed some categories of damages and vacated others for reconsideration. As of that ruling the government could still seek rehearing or Supreme Court review, the decision applied directly to a set of test properties while opening the door to further claims, and the amount and timing of compensation for the class was still being worked out in the trial court. The separate downstream case, brought by owners along Buffalo Bayou who flooded from the releases, was dismissed in 2020, revived on appeal in 2022 and remains pending on the court’s downstream docket. For a buyer, the practical meaning is that “in the flood pool” is now a legal status with a court record attached, and a seller who owns an upstream property has a specific disclosure obligation about it.

Sources: Texas Water Development Board, Addicks Reservoir and Barker Reservoir pages; U.S. Court of Appeals for the Federal Circuit, Ablan v. United States, Nos. 2023-1363 et al., December 22, 2025; U.S. Court of Federal Claims, In re Upstream Addicks and Barker (Texas) Flood-Control Reservoirs, Sub-Master Docket 17-9001L, opinion of December 17, 2019, and the downstream docket 17-9002; Houston Public Media, December 23, 2025; Texas Property Code Section 5.008. Retrieved August 24, 2026.

Step three: read the seller’s disclosure, all of it

Texas responded to Harvey by rewriting the seller’s disclosure. Senate Bill 339, effective September 1, 2019, amended Property Code Section 5.008 to add flood questions to the seller’s disclosure notice. The Texas Real Estate Commission’s promulgated form carrying them is the Seller’s Disclosure Notice, Form 55-1, whose current version took effect May 28, 2026. A seller of a single-family home must complete it, and these are the flood items, in the statute’s own words:

• “Present flood insurance coverage”
• “Previous flooding due to a failure or breach of a reservoir or a controlled or emergency release of water from a reservoir”
• “Previous water penetration into a structure on the property due to a natural flood event”
• “Located wholly / partly in a 100-year floodplain (Special Flood Hazard Area-Zone A, V, A99, AE, AO, AH, VE, or AR)”
• “Located wholly / partly in a 500-year floodplain (Moderate Flood Hazard Area-Zone X (shaded))”
• “Located wholly / partly in a floodway”
• “Located wholly / partly in a flood pool”
• “Located wholly / partly in a reservoir”
• “Have you (Seller) ever filed a claim for flood damage to the property with any insurance provider, including the National Flood Insurance Program (NFIP)?”
• “Have you (Seller) ever received assistance from FEMA or the U.S. Small Business Administration (SBA) for flood damage to the property?”

Three reading rules. First, the form asks what the seller is aware of; a seller who bought after 2017 may honestly not know what the house did in Harvey, so a “no” is not the same as “it did not flood.” Cross-check the map, the elevation and, where you can, the neighbors. Second, the reservoir-release and flood-pool questions exist because of Addicks and Barker, and for any address west of the Energy Corridor they are the ones to read most carefully. Third, the insurance-claim and FEMA-assistance questions are the closest thing to a flood history the law provides; a “yes” is not disqualifying, it is a reason to ask for the remediation record.

Tenants are covered too. Since January 1, 2022, Property Code Section 92.0135 requires a landlord to give a tenant a separate written notice, at or before signing, stating whether the landlord is or is not aware that the dwelling is in a 100-year floodplain, and to state separately if the landlord knows the dwelling flooded at least once in the five years before the lease. The statute’s form language tells the tenant that if neither box is checked, “you should assume the dwelling is in a 100-year floodplain.” For a relocating household that leases first, that notice is the first flood document you will see in Texas.

Sources: Texas Legislature Online, SB 339, 86th Legislature, history and enrolled text; Texas Property Code Sections 5.008 and 92.0135 (HB 531, 87th Legislature); Texas Real Estate Commission, Seller’s Disclosure Notice, Form 55-1 (effective May 28, 2026). Retrieved August 24, 2026.

Step four: insurance, required or not

Standard homeowners insurance does not cover flood. Flood coverage is a separate policy, written either through the National Flood Insurance Program or by a private insurer. A federally regulated or insured lender must require it when the home is in a Special Flood Hazard Area, which is to say in the A and V zones, and that covers most mortgages. Outside those zones no one requires it, and FEMA’s own note on the seller’s disclosure form encourages coverage in all zones.

The Harris County numbers are the argument for buying it anyway. Of the 154,170 homes that flooded in Harvey, the district reports that 55,570, or 36 percent, had a flood policy in effect when the storm began on August 24, 2017, and 64 percent did not. Most of those uninsured homes were outside the 100-year floodplain, where no lender required a policy and where a homeowner had been told, accurately, that the statistical chance in any year was low. The county’s Harvey report is the single most useful document a west Houston buyer can read on this subject, and it is free.

The national picture agrees with the county’s. FEMA reports that over the ten years from 2014 to 2024, nearly one-third of NFIP flood insurance claims, 29 percent, came from areas outside current high-risk flood zones. And since April 1, 2023, when FEMA fully implemented its Risk Rating 2.0 pricing approach, an NFIP premium is set for the individual property using flood frequency, the types of flooding it faces, distance to water, elevation and the cost to rebuild. The zone still decides whether a lender requires a policy; it no longer decides the price.

Practical rules: quote the specific address before you make an offer, because the price reflects the property’s own elevation and history rather than the zone alone, and a high quote on an unshaded-X home is information. Ask whether an elevation certificate exists; it tells you how the home sits relative to the base flood elevation. Know the waiting period: FEMA says there is typically a 30-day wait before an NFIP policy takes effect, but a policy bought in connection with a loan on the property has no waiting period and takes effect at closing, so a lender-required policy is not the problem; a voluntary one bought late is. And ask whether the current owner’s policy can be assigned.

Sources: Harris County Flood Control District, Immediate Flood Report, Hurricane Harvey 2017 (final); 42 U.S.C. Section 4012a(b); FEMA and FloodSmart (floodsmart.gov), flood risk, Risk Rating 2.0 and insurance professionals FAQ pages; Texas Property Code Section 5.008 footnote on flood insurance. Retrieved August 24, 2026. Insurance terms are set by the insurer and the program; confirm current rules with a licensed flood insurance agent.

Step five: know which rules the house was built under

Harvey also changed how west Houston builds, and a 2019 house and a 2005 house on the same street can have very different exposure because of it.

Inside the City of Houston, the City amended its Chapter 19 floodplain ordinance in 2018. Before the change, the city regulated the 100-year floodplain and required construction one foot above the 100-year flood elevation. After it, the city regulates both the 100-year and the 500-year floodplains and requires new construction and substantial improvements to be built two feet above the 500-year flood elevation.

In unincorporated Harris County, which includes most of the Katy-area subdivisions on the Harris side, the county’s Regulations for Floodplain Management took effect January 1, 2018 and were amended July 9, 2019. For new construction and substantial improvements, “the top of the subfloor of the lowest habitable floor must be elevated to twenty-four (24) or more inches above the 0.2 percent or 500-year flood elevation or twelve (12) inches above the level of the crown of the nearest public street, whichever is higher,” with 36 inches in a floodway. Fort Bend County and the City of Katy have their own rules.

For a buyer the consequence is simple: ask when the house was built or substantially improved, and under which jurisdiction’s rules. A home built to the post-2018 standard sits higher than its older neighbors by design, and that is worth paying for on a street with a flood history.

Sources: City of Houston Public Works, Chapter 19 comparison table (March 2018) and implementation schedule (July 2018); Harris County Engineering Department, Regulations for Floodplain Management, effective July 9, 2019, Section 4.07. Retrieved August 24, 2026.

Step six: the new maps are coming, and they are not here yet

Harris County’s flood maps are being redrawn for the first time since 2007. The program, MAAPnext, was launched by the Harris County Flood Control District with FEMA in 2019 and is the most comprehensive update since 2007, built on NOAA’s 2018 Atlas 14 rainfall estimates and new high-resolution LiDAR terrain data. The district’s own statement is unambiguous: “MAAPnext flood maps are currently in draft form and are being shared for informational and educational purposes only. Draft maps are provided for awareness only and are not open for formal comments or appeals. These draft maps are not final, cannot be used for insurance or regulatory decisions.” The district says FEMA is expected to release preliminary maps after its federal review, followed by a formal public review and appeal period. No effective date is published; the district publishes no timeline.

What that means for a purchase today: the effective zone is still the current map, and that is what the lender and the insurer use. But a home’s zone under the draft maps may differ, and if the draft moves it into a higher-risk category, the buyer who owns it when the maps take effect may face an insurance requirement the current owner does not. Ask us to check the draft data for any address you are serious about. It is not a reason to walk away; it is a reason to price and insure with the future map in view.

Sources: Harris County Flood Control District, MAAPnext (maapnext.org), status, background and innovation pages. Retrieved August 24, 2026.

Where to ask what, in west Houston

• West of the Energy Corridor toward Katy, north of I-10 around Addicks and south of it around Barker: the reservoir flood pool question. Read the disclosure’s flood pool, reservoir and reservoir-release lines and check the parcel against the Corps’ maximum pool.
• The Memorial area and the Memorial Villages: Buffalo Bayou elevation. The county reports record flooding at every bridge crossing in Harvey, with levels west of the 610 Loop five to eight feet above the Tax Day 2016 record, influenced by the reservoir releases. Elevation above the bayou is the question.
• The City of Katy: upper Buffalo Bayou and Cane Island Branch, where the county records “record flooding” through the city to Barker Reservoir, and where the record Barker pool overtopped the bayou’s banks near Fry Road and east of State Highway 99. The county counted 630 homes flooded in the Harris County portion of the city.
• Everywhere: local drainage. Most of the county’s Harvey flooding was outside any mapped floodplain, and the street’s drainage, the lot’s grade and the nearest detention pond are the questions a map cannot answer. Ask the neighbors what the street did in August 2017.

How to buy well here

Buying in a flood-aware market is not about avoiding every zone. The Energy Corridor, Memorial and Katy would empty out if it were. It is about matching price and insurance to the parcel’s actual facts and knowing the difference between a house that flooded once in a 154,170-home storm and one that floods in an ordinary spring. In practice:

1. Pull the FEMA zone and the county’s map for the address before the first showing, not after the offer.
2. Read every flood line on the seller’s disclosure and, for anything west of the corridor, the flood pool and reservoir lines twice.
3. Quote flood insurance on the address regardless of zone. Treat a high quote as information.
4. Ask for the elevation certificate, the build date and jurisdiction, and, if the home flooded, the remediation record.
5. Check the draft MAAPnext data for the address, so the next map cycle does not surprise you.
6. Price the house on those facts. A well-remediated, well-insured home on a street with a known history can be the better buy; a never-flooded home on an unshaded-X lot with no drainage can be the worse one.

Our founder’s own view has not changed since she wrote in 2020 that the brokerage had survived the oil downturn and Harvey and intended to keep standing. The market did the same. It just reads the disclosure more carefully now.

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