FloodMaps

Our data · Source of truth

Every source behind your report

A FloodMaps report combines public flood maps, elevation surveys, storm records, county property records, and community reports for homes in the Houston area and Florida. This page lists every one of them: who publishes it, what we take from it, how accurate and current it is, and where it covers, so you can check any number in your report against the original.

It's the reference we keep up to date. If something here and something in a report disagree, this page describes how it's supposed to work, and we want to hear about it.

Last reviewed October 13, 2026

Where we cover

Address search covers the Houston metro area and all 67 Florida counties. In Houston, the full report, with county property records, Hurricane Harvey estimates for each home, and the county-wide ranking, is for Harris County. Street-flooding reports there come from City of Houston 311, so they only exist inside city limits.

Every Florida county gets flood zones, FEMA's draft maps where it has issued them, ground height, property records from the state tax roll, past storms since 2016, and a ranking against other Florida homes. Florida street-flooding reports come only from Miami-Dade County, Broward County, the City of Tampa, and Leon County. Ground height uses 0.5 m lidar across the Houston lidar area, the newest lidar survey that covers each Florida lot, and USGS 3DEP elsewhere.

  • City of Houston

    Everything, including 311 street-flooding reports.

    Flood zones
    Yes
    Ground height
    Yes
    Past storms
    Yes
    Property records
    Yes
    Street-flooding reports
    Yes
    Rating & ranking
    Yes

  • Rest of Harris County

    Everything except 311, which only the City of Houston publishes.

    Flood zones
    Yes
    Ground height
    Yes
    Past storms
    Yes
    Property records
    Yes
    Street-flooding reports
    No
    Rating & ranking
    Yes

  • Galveston, Fort Bend, Brazoria, and Montgomery counties

    Flood zones, ground at the house, Harvey water against the floor (except Montgomery County and two ZIPs where FEMA's Harvey map disagrees with flood-insurance claims and FEMA aid records), and the Houston-area ranking. County records come from each appraisal district where published: year built for Galveston and Fort Bend, part of Brazoria, none yet for Montgomery. Home-by-home 2017 damage records and 311 are Harris-only.

    Flood zones
    Yes
    Ground height
    Yes
    Past storms
    Partly
    Property records
    Partly
    Street-flooding reports
    No
    Rating & ranking
    Yes

  • Florida, all 67 counties

    FEMA flood zones and draft maps where FEMA has issued them, ground at the house, county property records from the state tax roll, flood claims and FEMA aid from 14 storms since 2016, and a rating ranked against other Florida homes. Home-by-home damage records exist only where FEMA or the county inspected after a storm. Street-flooding reports only in Miami-Dade County, Broward County, the City of Tampa, and Leon County.

    Flood zones
    Yes
    Ground height
    Yes
    Past storms
    Yes
    Property records
    Yes
    Street-flooding reports
    Partly
    Rating & ranking
    Yes

  • Miami-Dade County, Broward County, the City of Tampa, and Leon County

    Everything else in a Florida report, plus street-flooding reports made to the county or city. Miami-Dade's records run 2013 to 2023; the county stopped publishing them after that.

    Flood zones
    Yes
    Ground height
    Yes
    Past storms
    Yes
    Property records
    Yes
    Street-flooding reports
    Yes
    Rating & ranking
    Yes

  • Outside the Houston metro and Florida

    Not supported yet: address search is limited to the Houston metro area and Florida.

    Flood zones
    No
    Ground height
    No
    Past storms
    No
    Property records
    No
    Street-flooding reports
    No
    Rating & ranking
    No

Data sources

43 sources, grouped by what they tell you. Badges show how official each one is: Official is a government record, Draft is not yet in effect, Model is an agency's estimate, Measured is an instrument reading, Reported comes from residents, and Open data and Commercial are non-government providers.

Flood maps & zones

OfficialLive, cached

FEMA National Flood Hazard Layer (NFHL)

Federal Emergency Management Agency (FEMA)

What we use
Flood zone (FLD_ZONE, ZONE_SUBTY), high-risk flag (SFHA_TF), static base flood elevation, zone depth, and the nearest base flood elevation line.
Where you see it
Overview zone tiles · FEMA Zones tab · Floor vs. flood line · Risk score · Map layer · PDF report
Resolution
Regulatory polygons and flood-line polylines. Flood lines are searched within 500 m of the lot.
Accuracy
This is the official effective map. Zone lines follow FEMA's digitized boundaries, which can be off from the ground by tens of feet. A Letter of Map Change issued after the last refresh may not be reflected yet.
Data from
Current effective FIRM panels
Updates
Checked live; our Harris County copy is refreshed about monthly to pick up map changes.
Coverage
Nationwide (Harris County mirrored).
License
U.S. Government work, public domain
Check it yourself
FEMA Flood Map Service Center(opens in a new tab)
DraftLive, cached

MAAPnext draft flood hazard maps

Harris County Flood Control District (HCFCD)

What we use
Draft zone at the lot (floodway, Zone AE, 0.2% / Shaded X, community flooding, minimal X), draft flood line where published, and the draft map tiles for the side-by-side view.
Where you see it
Today vs. the 2026 draft · Flood zones around you · Overview draft tile · Risk score (draft maps factor)
Resolution
Thematic raster at about 1 m, sampled at the lot.
Accuracy
A draft in public review, not a regulatory map. Zones and flood lines can change before FEMA adopts them. Today's effective FEMA zone still sets insurance rules.
Data from
2026 draft release
Updates
Read live from HCFCD's map service; a stored copy is used if the service is down.
Coverage
Watersheds HCFCD has modeled in Harris County.
Check it yourself
MAAPnext(opens in a new tab)
DraftLive

FEMA preliminary and in-review flood maps

FEMA

What we use
Preliminary zone at the lot where FEMA has issued preliminary panels, and non-regulatory in-review data. Used before MAAPnext when both exist.
Where you see it
Today vs. the 2026 draft · Overview draft tile
Resolution
Regulatory-style polygons.
Accuracy
Not yet effective. Preliminary maps can change through appeals before adoption.
Data from
As issued by FEMA
Updates
Checked live.
Coverage
Areas with issued preliminary or in-review data (parts of north Harris and south Montgomery counties today).
License
U.S. Government work, public domain
Check it yourself
FEMA Flood Map Changes Viewer(opens in a new tab)
OfficialLive

Federal Register: FEMA flood hazard determinations

Office of the Federal Register (National Archives) for FEMA

What we use
FEMA's proposed and final flood hazard determinations for the counties we cover: the communities affected, the appeal period, and the date new maps take effect.
Where you see it
Flood News map change posts
Resolution
One notice per FEMA map project, listed by community.
Accuracy
The official notice of record. The maps it announces are in FEMA's Flood Map Service Center, and the dates can move if appeals are filed.
Data from
As published, weekdays
Updates
Checked every 6 hours.
Coverage
Nationwide; we follow the counties we cover.
License
U.S. Government work, public domain
Check it yourself
Federal Register: FEMA documents(opens in a new tab)
OfficialImported

Florida Coastal Construction Control Line

Florida Department of Environmental Protection

What we use
Distance from the home to the line that marks where the state's coastal construction rules start.
Where you see it
FEMA Zones tab · First-floor height
Resolution
The adopted line along each county's sandy beaches.
Accuracy
A permitting line, not a flood boundary. The state's own survey decides whether a lot sits seaward of it.
Data from
Lines adopted 1981 to 2010
Updates
Static; re-imported when the state re-adopts a county's line.
Coverage
Florida's sandy-beach coastal counties.
Check it yourself
Florida DEP coastal construction control line(opens in a new tab)

Elevation & terrain

MeasuredLive, cached

2024 Houston lidar elevation (USGS OPR TX_Houston_B24)

U.S. Geological Survey (USGS), 3D Elevation Program

What we use
Bare-earth ground elevation at the lot and around it: the ground at the house, lot high and low, slope, and the cross-section.
Where you see it
Elevation & Ground tab · Floor vs. flood line · Lot vs. block · Risk score (height factors) · 3D lot view
Resolution
0.5 m digital elevation model.
Accuracy
Typical vertical accuracy for USGS Quality Level 1 lidar is about 10 cm (RMSE). Under buildings, trees, and water the ground is interpolated. It measures the ground, not your floor height.
Data from
Collected 2024
Updates
Static; sampled on demand and stored per lot.
Coverage
The Houston lidar footprint (most of the Houston region).
License
U.S. Government work, public domain
Check it yourself
USGS National Map downloader(opens in a new tab)
MeasuredLive, cached

USGS 3DEP elevation (best available)

USGS, 3D Elevation Program

What we use
Ground elevation when the lot is outside the 2024 Houston lidar footprint.
Where you see it
Elevation & Ground tab · Floor vs. flood line
Resolution
Best available: 1 m lidar where flown, otherwise about 10 m.
Accuracy
Depends on the underlying survey; 10 m data smooths small features like curbs and swales.
Data from
Varies by area
Updates
Sampled on demand and stored.
Coverage
Continental U.S.
License
U.S. Government work, public domain
Check it yourself
USGS 3D Elevation Program(opens in a new tab)
MeasuredLive, cached

Florida lidar elevation (USGS original-resolution surveys)

USGS, 3D Elevation Program

What we use
Bare-earth ground elevation at the lot and around it, from the newest survey that covers it: the ground at the house, lot high and low, slope, and the cross-section.
Where you see it
Elevation & Ground tab · Floor vs. flood line · Lot vs. block · Risk score (height factors) · 3D lot view
Resolution
Each survey's own grid, usually 1 m or finer.
Accuracy
USGS Quality Level 2 or better: about 10 cm vertical accuracy (RMSE). Every survey is converted to feet above NAVD88, whatever projection and unit it shipped in. Under buildings, trees, and water the ground is interpolated. It measures the ground, not your floor height.
Data from
Varies by county; the newest survey covering the lot is used
Updates
Sampled on demand and stored per lot; a newer survey is used once USGS publishes it.
Coverage
Florida, wherever USGS has published an original-resolution survey.
License
U.S. Government work, public domain
Check it yourself
USGS National Map downloader(opens in a new tab)
MeasuredLive, cached

NOAA 2017 Hillsborough County lidar elevation

NOAA Office for Coastal Management (Digital Coast)

What we use
Ground elevation in Hillsborough County, where this is the newest lidar survey.
Where you see it
Elevation & Ground tab · Floor vs. flood line · 3D lot view
Resolution
2.5 ft (about 0.76 m) grid.
Accuracy
Quality Level 1 lidar: about 10 cm vertical accuracy (RMSE). It measures the ground, not your floor height.
Data from
Collected 2017
Updates
Static; sampled on demand and stored per lot.
Coverage
Hillsborough County.
License
U.S. Government work, public domain
Check it yourself
NOAA Data Access Viewer(opens in a new tab)

Flood history

ModelImported

FEMA Hurricane Harvey final depth grid

FEMA (Harvey_Depths_3m_v3, final November 15, 2017)

What we use
Harvey's water level around the house: ground plus grid depth on the land 8 to 35 m out, corrected to USGS high-water marks, compared with the floor.
Where you see it
Overview Flood history · Harvey at this home · Risk score (floor vs. flood levels, flooded here before) · Harvey map layer
Resolution
About 3 m cells.
Accuracy
Checked by us against paid NFIP claims: mean absolute error 0.91 ft across 439 block groups. Against USGS high-water marks: median absolute difference 0.80 ft, 61% within 1 ft. It is interpolated from surveyed marks, not measured at each house.
Data from
August 2017 (final November 2017)
Updates
Static.
Coverage
Harris County.
License
U.S. Government work, public domain
Check it yourself
TACC Harvey data archive(opens in a new tab)
ModelImported

FEMA Harvey modeled building damage (merged with HCAD)

FEMA (2017), merged with HCAD by an open public project

What we use
Damage level per building (affected, minor, major, destroyed), modeled water inside, and the building's HCAD year built and size. Matched to the home within 40 m.
Where you see it
Harvey within ¼ mile · Overview Flood history · ZIP flood map pages
Resolution
One point per modeled building.
Accuracy
Undercounts: it places water in about 52,860 single-family homes, 34% of the 154,170 Harris County Flood Control counted. Treat neighborhood counts as a floor ("at least").
Data from
September 2017
Updates
Static.
Coverage
Harris County.
Check it yourself
Harvey FEMA–HCAD merge (GitHub)(opens in a new tab)
MeasuredLive, cached

USGS stream gauges (water level)

USGS Water Data

What we use
Water level (gage height) at the nearest gauge through six named storms: Memorial Day 2015, Tax Day 2016, Harvey 2017, Imelda 2019, the 2024 derecho, and Beryl 2024. We show the rise above the pre-storm level.
Where you see it
The bayou in each storm · Where these records come from · Overview storm marks
Resolution
Readings every 15 minutes at the gauge.
Accuracy
Measured at the gauge, which can be miles from the home. Rise at the bayou is not water at the house.
Data from
2015 to 2024 storms
Updates
Storm readings refreshed monthly; gauge list refreshed as USGS adds sites.
Coverage
Gauges near Harris County (bundled list); live search elsewhere.
License
U.S. Government work, public domain
Check it yourself
USGS Water Data(opens in a new tab)
MeasuredImported

USGS Harvey high-water marks

USGS Short-Term Network

What we use
Surveyed Harvey water elevations, used to measure where FEMA's depth grid runs high or low and correct its water level near each house. Never shown on their own.
Where you see it
Harvey at this home · Risk score (Harvey water vs. floor)
Resolution
About 990 marks with a surveyed water elevation across Harris, Galveston, Fort Bend, Brazoria, and Montgomery counties.
Accuracy
Surveyed to within a few hundredths to tenths of a foot, but marks sit where water reached, not at a house.
Data from
2017
Updates
Static.
Coverage
Five Houston-area counties (Harvey event).
License
U.S. Government work, public domain
Check it yourself
USGS Flood Event Viewer(opens in a new tab)
OfficialLive

HCFCD channels, detention basins, and watersheds

Harris County Flood Control District (HCFCD)

What we use
Watershed name, nearest channel and its distance, and nearest detention basin.
Where you see it
Risk score (drainage) · Rating breakdown · Map layers
Resolution
Mapped channel and basin outlines.
Accuracy
Distances are straight-line to the mapped channel, not the drainage path.
Data from
Current HCFCD GIS
Updates
Checked live.
Coverage
Harris County.
Check it yourself
Harris County Flood Control District(opens in a new tab)
OfficialLive, cached

USGS National Hydrography Dataset (streams and canals)

USGS

What we use
Distance from the house to the nearest stream, bayou, ditch, or canal on USGS's national stream map.
Where you see it
Harvey at this home · Risk score (drainage)
Resolution
Mapped flowlines at about 1:24,000.
Accuracy
Distances are straight-line to the mapped line, not the drainage path. Small ditches and storm pipes aren't mapped.
Data from
Current national release
Updates
Read on demand and stored per place.
Coverage
Nationwide.
License
U.S. Government work, public domain
Check it yourself
USGS National Hydrography Dataset(opens in a new tab)
MeasuredImported

NOAA tide gauges (storm peaks)

NOAA Center for Operational Oceanographic Products and Services

What we use
The highest verified water level at the nearest tide gauge in each storm since 2016, in feet above the normal high tide (MHHW), and the level before the storm.
Where you see it
Water levels in past storms
Resolution
Six-minute readings at the gauge.
Accuracy
Measured at the gauge, which can be miles from the home. Surge changes a lot along a coast and up a bay.
Data from
2016 to 2024 storms
Updates
Static; extended when a new storm is added.
Coverage
23 NOAA water-level stations around Florida.
License
U.S. Government work, public domain
Check it yourself
NOAA Tides & Currents(opens in a new tab)
OfficialImported

FEMA historical damage assessments

FEMA

What we use
Damage level per building after Hermine (2016), Irma (2017), and Michael (2018), and water depth where FEMA recorded it, matched to the home within 40 m.
Where you see it
Storms at this home · Overview Flood history
Resolution
One point per assessed building.
Accuracy
Assessed from aerial imagery and field visits soon after each storm. Not every building was assessed, so a missing record doesn't mean the home was spared.
Data from
2016 to 2018 storms
Updates
Static.
Coverage
Florida areas FEMA assessed after those storms.
License
U.S. Government work, public domain
Check it yourself
FEMA Historical Geospatial Damage Assessment Database(opens in a new tab)
OfficialImported

County storm damage assessments (Hillsborough, Pinellas, and Lee)

Hillsborough County, Pinellas County, and Lee County

What we use
Damage level per building after Ian (2022, Lee County's islands) and Debby, Helene, and Milton (2024), with water depth where recorded, matched to the home within 40 m.
Where you see it
Storms at this home · Overview Flood history
Resolution
One point per inspected building.
Accuracy
County inspectors' field ratings in the days after each storm. Buildings they didn't reach have no record.
Data from
2022 and 2024 storms
Updates
Static.
Coverage
Hillsborough County (2024), Pinellas County (Helene), and Lee County's islands (Ian).
Check it yourself
Hillsborough County 2024 damage assessments(opens in a new tab)
OfficialImported

South Florida Water Management District canals and basins

South Florida Water Management District (SFWMD)

What we use
The nearest canal and its distance, and the drainage basin the home is in.
Where you see it
Drainage · Risk score (drainage)
Resolution
Mapped canal centerlines and basin outlines.
Accuracy
Distances are straight-line to the mapped canal, not the drainage path.
Data from
Current SFWMD GIS
Updates
Re-imported when the district updates its maps.
Coverage
The 16 counties of the South Florida Water Management District.
Check it yourself
SFWMD GIS open data(opens in a new tab)
OfficialImported

USGS Watershed Boundary Dataset (HUC-12)

USGS

What we use
The name of the small watershed the home drains to, where the water management district's basins don't apply.
Where you see it
Drainage
Resolution
12-digit hydrologic units (about 40 square miles each).
Accuracy
National watershed lines; local drainage can cross them through pipes and canals.
Data from
Current national release
Updates
Re-imported with USGS releases.
Coverage
Florida.
License
U.S. Government work, public domain
Check it yourself
USGS Watershed Boundary Dataset(opens in a new tab)

Rainfall

OfficialLive, cached

NOAA Atlas 14 precipitation frequency

NOAA National Weather Service, Hydrometeorological Design Studies Center

What we use
Rainfall depth for 1 hour to 3 days at 2- to 500-year return periods, at the home's coordinates.
Where you see it
Rainfall in big storms · Risk score (rainfall)
Resolution
Point estimate from NOAA's gridded statistics.
Accuracy
NOAA publishes 90% confidence bounds with each value (shown on NOAA's site). Based on the historical record through the study date.
Data from
Texas volume (Atlas 14 Volume 11, 2018)
Updates
Static climatology; read on demand.
Coverage
Atlas 14 project area (includes Texas).
License
U.S. Government work, public domain
Check it yourself
NOAA Precipitation Frequency Data Server(opens in a new tab)
OfficialLive

National Hurricane Center advisories

NOAA National Hurricane Center (NHC)

What we use
Active storms and, from each public advisory, the storm's position, strength, watches, and warnings, plus the forecast cone graphic.
Where you see it
Flood News storm trackers and recaps
Resolution
Storm-level forecasts, updated with each advisory.
Accuracy
The official forecast. The cone shows where the center will probably go, not how far flooding and rain will reach.
Data from
Current Atlantic hurricane season
Updates
Checked every 15 minutes while a storm is active.
Coverage
Atlantic basin; we follow storms that threaten Texas or Florida.
License
U.S. Government work, public domain
Check it yourself
National Hurricane Center(opens in a new tab)

Property & parcels

OfficialLive, cached

HCAD parcels (live)

Harris Central Appraisal District (HCAD)

What we use
Account number, site address, land use, lot size, lot outline, and land, building, and total appraised values. Owner names aren't used.
Where you see it
Property Info tab · Appraised value · The lot · Where these facts come from · Risk score (land use) · Map parcels
Resolution
Parcel polygon per account.
Accuracy
The county's record for tax purposes. Lot lines are GIS outlines, not a survey. Values are appraisal values, not market prices.
Data from
Current tax year
Updates
Read live and stored per address.
Coverage
Harris County.
Check it yourself
HCAD property search(opens in a new tab)
OfficialImported

HCAD public data export

Harris Central Appraisal District (HCAD)

What we use
Year built, living area, and appraisal values for every single-family home, used to rank homes county-wide and compare a home with its neighbors and ZIP. From the building records: foundation type, stories, exterior walls, any lower level or garage below the main floor, remodel year, condition, and build quality.
Where you see it
Compared with nearby homes · Age and size · House details · First-floor height · Risk ranking · Similar homes nearby
Resolution
One record per account; single-family (state class A1) homes only.
Accuracy
County records can be wrong or out of date, especially after remodels or rebuilds. You can correct year built, living area, foundation, stories, and walls in the report.
Data from
Latest tax-year export
Updates
Re-imported when HCAD publishes a new export.
Coverage
Harris County.
Check it yourself
HCAD public data(opens in a new tab)
OfficialLive, cached

Florida statewide parcels

Florida Department of Revenue, from the 67 county property appraisers (published by the Florida Geographic Information Office)

What we use
Parcel ID, owner, site address, land use, lot outline, lot size, year built, living area, and just value split into land and building.
Where you see it
Property Info tab · Appraised value · The lot · Where these facts come from · Map parcels
Resolution
Parcel polygon per account; condo units share their building's lot.
Accuracy
The county's record for tax purposes, sent to the state each July. Lot lines are GIS outlines, not a survey. Just value is the county's estimate of market value for taxes, not a sale price.
Data from
Latest roll sent to the state
Updates
Read live and stored per address.
Coverage
All 67 Florida counties.
Check it yourself
Florida Statewide Cadastral(opens in a new tab)
OfficialImported

Florida Department of Revenue tax roll (name-address-legal file)

Florida Department of Revenue

What we use
Year built, living area, lot size, buildings, units, and values for every parcel, used to compare a home with its neighbors and ZIP, count a condo building's units, and rank homes across Florida.
Where you see it
Compared with nearby homes · Age and size · House details · Risk ranking
Resolution
One record per parcel.
Accuracy
County records can be wrong or out of date, especially after remodels or rebuilds. Living area is the county's adjusted area, which can differ from heated square feet. You can correct year built and living area in the report.
Data from
2026 roll (final where the county has certified it, preliminary elsewhere)
Updates
Checked weekly for a new release and re-imported when the state publishes one.
Coverage
All 67 Florida counties.
Check it yourself
Florida Department of Revenue data portal(opens in a new tab)
OfficialImported

County elevation certificates (Pinellas, Charlotte, and Miami Beach)

Pinellas County, Charlotte County, and the City of Miami Beach

What we use
The surveyed lowest-floor height, ground beside the house, base flood elevation, and survey date on the certificate filed for the home, matched within 10 m or by house number.
Where you see it
First-floor height · Floor vs. flood line · Risk score (floor vs. flood levels)
Resolution
One certificate per surveyed building.
Accuracy
A licensed surveyor's measurement on the survey date; a home raised or rebuilt since will differ. Certificates in the older NGVD29 datum are converted to NAVD88 with NOAA's conversion grid.
Data from
Pinellas 1960 to 2024; Charlotte and Miami Beach as published
Updates
Re-imported when a county updates its layer.
Coverage
Pinellas County, Charlotte County, and the City of Miami Beach.
Check it yourself
About elevation certificates (FEMA)(opens in a new tab)

Insurance & claims

OfficialLive, cached

OpenFEMA NFIP policies (redacted)

FEMA, National Flood Insurance Program

What we use
Premiums, coverage, and rated zone on in-force single-family policies near the home, grouped by ZIP or census block group (at least 8 policies).
Where you see it
What neighbors pay for flood insurance · Flood insurance estimate tile · Today vs. the 2026 draft
Resolution
ZIP or census block group; addresses are redacted by FEMA.
Accuracy
What nearby policyholders pay, not a quote for this home. Risk Rating 2.0 prices each home individually.
Data from
Current policy extract
Updates
Read on demand, refreshed weekly.
Coverage
Nationwide.
License
U.S. Government work, public domain
Check it yourself
OpenFEMA NFIP policies dataset(opens in a new tab)
OfficialImported

OpenFEMA NFIP claims (redacted), Hurricane Harvey

FEMA, National Flood Insurance Program

What we use
Count of paid single-family Harvey flood claims per 2010 census block group, and claim water depths for our validation.
Where you see it
Harvey within ¼ mile · Overview Flood history · Where these records come from
Resolution
Census block group; addresses redacted.
Accuracy
Only insured homes appear; about a third of flooded homes in Harvey had flood insurance, so counts are a floor.
Data from
Harvey 2017 claims
Updates
FEMA refreshes the dataset every few months. We check daily, and the report shows the refresh our counts come from.
Coverage
Harris County.
License
U.S. Government work, public domain
Check it yourself
OpenFEMA NFIP claims dataset(opens in a new tab)
OfficialImported

OpenFEMA Individuals and Households Program registrations (Harvey, DR-4332)

FEMA

What we use
Number of aid requests per ZIP, split by owners and renters, and grant amounts by size. County totals on the Houston map and the Harris County page add up these ZIP counts, with each ZIP counted in the county that holds most of its single-family homes.
Where you see it
Harvey across ZIP · Where these records come from · ZIP flood map pages · Harris County flood map
Resolution
ZIP code.
Accuracy
FEMA's public extract carries no water-depth or damage values for Harvey, so we show what was paid, not how badly homes flooded.
Data from
Harvey 2017
Updates
Static.
Coverage
Every ZIP in the Harvey disaster declaration (787 ZIPs).
License
U.S. Government work, public domain
Check it yourself
OpenFEMA IHP dataset(opens in a new tab)
OfficialLive, cached

U.S. Census TIGER block groups (2010)

U.S. Census Bureau

What we use
Block group boundaries to group claims and policies near a home.
Where you see it
Harvey within ¼ mile · What neighbors pay for flood insurance · Harvey claims map layer
Resolution
Block group polygons.
Accuracy
Administrative boundaries; matched to the vintage FEMA used in its records.
Data from
2010
Updates
Static.
Coverage
Nationwide.
License
U.S. Government work, public domain
Check it yourself
Census TIGERweb(opens in a new tab)
OfficialImported

FEMA Community Status Book (NFIP and Community Rating System)

FEMA

What we use
The community's first flood map date (which makes a home pre- or post-FIRM), its current map date, its Community Rating System class, and the insurance discount that class gives.
Where you see it
First-floor height · Flood insurance estimate tile · Property Info tab
Resolution
One record per NFIP community (a city, town, or the unincorporated county).
Accuracy
FEMA's official list. Community Rating System classes change each April and October.
Data from
Current book
Updates
Refreshed monthly.
Coverage
Every NFIP community in Florida and Texas.
License
U.S. Government work, public domain
Check it yourself
FEMA Community Status Book(opens in a new tab)

Community reports

ReportedLive

City of Houston 311 service requests

City of Houston

What we use
Flooding, drainage, stagnant water, and sewer requests within 1,000 ft: type, date, status, and location.
Where you see it
Street flooding reports · Overview 311 card · Where these records come from · Risk score (311 reports)
Resolution
One point per request (block-level address).
Accuracy
Reports from residents, not measurements. Busy streets and engaged neighborhoods report more. The city's current records start July 2021.
Data from
July 2021 to today
Updates
Read live.
Coverage
City of Houston only. Other cities (Bellaire, Pasadena) and unincorporated Harris County keep separate records, so this factor is left out there.
Check it yourself
Houston 311(opens in a new tab)
ReportedLive, cached

City of Tampa street flooding reports

City of Tampa

What we use
Street flooding reports and stormwater advisories near the home: type, date, status, and location.
Where you see it
Street flooding reports · Risk score (street flooding reports)
Resolution
One point per report.
Accuracy
Reports from residents and city crews, not measurements. Busy streets report more.
Data from
October 2024 to today
Updates
Read live; the stormwater advisory history is saved.
Coverage
City of Tampa only.
Check it yourself
City of Tampa Stormwater(opens in a new tab)
ReportedLive, cached

Leon County Public Works flooding and drainage requests

Leon County

What we use
Flooding and drainage service requests near the home: type, date, status, and location.
Where you see it
Street flooding reports · Risk score (street flooding reports)
Resolution
One point per request.
Accuracy
Requests from residents, not measurements. The county's records start August 2016.
Data from
August 2016 to today
Updates
Read live.
Coverage
Leon County (Tallahassee area).
Check it yourself
Leon County Public Works service requests(opens in a new tab)
ReportedImported

Broward County "Document the Floods" reports

Broward County

What we use
Flooding reports residents filed near the home: date, water depth where given, and location.
Where you see it
Street flooding reports · Risk score (street flooding reports)
Resolution
One point per report.
Accuracy
Voluntary reports from residents; most neighborhoods have few or none.
Data from
October 2016 to today
Updates
New reports are added weekly.
Coverage
Broward County.
Check it yourself
Broward County Document the Floods(opens in a new tab)
ReportedImported

Miami-Dade County 311 flooding requests (2013 to 2023)

Miami-Dade County

What we use
Flooding and drainage 311 requests near the home from 2013 through 2023: type, date, and location.
Where you see it
Street flooding reports · Risk score (street flooding reports)
Resolution
One point per request.
Accuracy
Requests from residents, not measurements. The county stopped publishing these records after 2023, so recent flooding isn't included.
Data from
2013 to 2023
Updates
Static.
Coverage
Miami-Dade County.
Check it yourself
Miami-Dade County open data(opens in a new tab)

Ground movement

MeasuredImported

Harris-Galveston Subsidence District GPS rates

Harris-Galveston Subsidence District (HGSD)

What we use
Yearly ground movement at the nearest GPS station, used only when it's within 6 miles.
Where you see it
Is the ground sinking? · Where these heights come from · Risk score (ground sinking)
Resolution
One rate per station.
Accuracy
A station's trend, not a measurement at the house. Rates can differ a few miles apart.
Data from
HGSD 2021 to 2025 rates
Updates
Refreshed when HGSD publishes its annual report.
Coverage
Harris, Galveston, and Fort Bend area stations.
Check it yourself
Harris-Galveston Subsidence District(opens in a new tab)
ReportedImported

Florida Geological Survey subsidence incident reports

Florida Geological Survey, Department of Environmental Protection

What we use
Reported sinkholes and ground subsidence within a mile of the home, with the date and whether the survey confirmed a true sinkhole, plus the county's total.
Where you see it
Sinkholes nearby · Where these records come from
Resolution
One point per reported incident.
Accuracy
Reports from the public and agencies, not all field-checked, and some locations are approximate, so only well-located reports are shown nearby. A report is not a sinkhole risk rating.
Data from
1909 to today
Updates
Refreshed weekly.
Coverage
Florida.
Check it yourself
Florida Geological Survey sinkholes(opens in a new tab)

Buildings & streets

Open dataImported

Overture Maps buildings and roads

Overture Maps Foundation

What we use
Building outlines on the lot (house and outbuildings), building heights where known, and road names and classes.
Where you see it
The lot · 3D lot view · Floor vs. flood line · Where these facts come from
Resolution
Building footprint polygons.
Accuracy
Open data built from OpenStreetMap and other sources; outlines can be missing, merged, or a few feet off.
Data from
Recent Overture release
Updates
Re-imported with Overture releases (about quarterly).
Coverage
Harris County area.
License
ODbL and CDLA (per Overture theme)
Check it yourself
Overture Maps Foundation(opens in a new tab)
Open dataLive, cached

OpenStreetMap

OpenStreetMap contributors

What we use
Nearby named streets for context, and the base data inside our maps.
Where you see it
Maps · Street names in the 3D view
Resolution
Street centerlines.
Accuracy
Community-edited; generally current in Houston.
Data from
Current
Updates
Read on demand.
Coverage
Worldwide.
License
ODbL
Check it yourself
OpenStreetMap copyright(opens in a new tab)

AI

CommercialLive

Google Gemini

Google

What we use
Writes the plain-language summary and answers your questions using only the numbers already in the report. It adds no new data.
Where you see it
AI summary · Ask FloodMaps AI
Resolution
Not applicable.
Accuracy
Language models can misread or misstate numbers. Every figure it cites is in the report, so check it there.
Data from
Current model
Updates
Summaries are kept for a while so the same report reads the same.
Coverage
All reports.
Check it yourself
Google AI(opens in a new tab)

How we build a report

What we calculate from the sources above, what goes into each number, and where it stops being reliable.

What the risk score weighs

  • 50%Floor vs. flood levelsHow high the living floor sits against FEMA's flood line and Harvey's water level
  • 20%Flooded here beforeHarvey's water against this house's floor; share of nearby homes it got into
  • 20%Flood zoneFEMA zone today; the 2026 draft maps
  • 10%Local areaDistance to a bayou or channel; 311 reports; 100-year rainfall

Shares when every factor has data; they re-balance when one is missing.

Risk score and rating

Uses
FEMA zones and draft maps, lidar ground at the house, county building records, FEMA's Harvey depth grid corrected to USGS high-water marks, NOAA rainfall, flood-control channels, and 311 reports.
How
Every home is scored 0–100 on four drivers: how high its living floor sits against FEMA's flood line and Harvey's water level (50%), whether Harvey's water got above this floor and into nearby homes (20%), the flood zone today and on the draft maps (20%), and the local area: channels, 311 reports, and rain (10%). Ground and Harvey water are measured at the house itself, not the middle of the lot. Harvey only counts against a house that was standing in 2017. A driver without data hands its weight to the others, and at least three are needed (two where there's no reliable Harvey map). The weighted total is ranked against every scored single-family home in Harris, Galveston, Fort Bend, Brazoria, and Montgomery counties, and the score you see is that rank: 92 means riskier than 92% of them. The rank sets the rating: 95 and up is Severe, 85–94 High, 65–84 Moderate, 40–64 Low, and under 40 Minimal. Two floors apply: homes in FEMA's high-risk zone are never rated below Moderate (or Low when the floor is 1 ft or more above the flood line), and homes where Harvey's water rose a foot or more above the living floor are never rated below High. Owners who bought the report can refine their own home's facts, which re-scores it for them only.
Limits
A comparison between homes, not a probability of flooding. The floor is an estimate unless the owner gives it. Missing data changes which drivers count but never counts as safe. Homes outside the five counties are placed among their homes but aren't part of the ranking.

First-floor height

Uses
Ground under the house's outline from lidar, plus your elevation certificate, your measured floor height, your foundation type, the county's building record (foundation, lower-level garage or living area), building rules for the year built, or the year built alone.
How
We use the best input available, in this order: an elevation certificate number you enter, a floor height you enter, a foundation type you pick, the county's recorded foundation, or a foundation typical for the year built. Unless you gave the floor itself, building rules set a minimum: homes built since 2018 in a 100- or 500-year zone sit at least 2 ft above the flood line, and homes built in a high-risk zone after FEMA's first maps sit about at it. A garage or lower level below the living floor is tracked as its own, lower floor.
Limits
Unless you enter a certificate number, it is an estimate and can be off by a foot or more. County records can be wrong. Only a licensed surveyor's elevation certificate is authoritative.

Chance of a flood while you own it

Uses
FEMA's yearly chance for the zone (1% for A and V zones, 0.2% for Shaded X, lower for Zone X) and the years left on your mortgage.
How
The yearly chance is compounded over the years you'll own the home: 1 − (1 − yearly chance)^years.
Limits
Uses the zone's chance, not this home's. A low floor or past flooding can make the real chance higher.

Harvey water at the home

Uses
FEMA's final Harvey depth grid, lidar ground, and USGS surveyed high-water marks.
How
Harvey's water level is the ground plus the grid's depth on a ring of land 8 to 35 m around the house, taking the middle value, then pulled toward the water levels USGS surveyed at nearby high-water marks: bay marks near sea level within about 2 km, reservoir marks that far only for homes in the same pool, bayou marks within a few hundred meters. That level is compared with the house's floor, within half a foot either way counting as "about at the floor". A house built after 2017 has no Harvey record; the page shows what that water would do to today's floor.
Limits
An estimate of 2017, not a measurement inside the house, and not a prediction. Away from marks the grid's level stands as is. Floors are estimated (a slab floor at about 14 in above the ground) unless the owner gives theirs.

Comparisons with nearby homes

Uses
HCAD records and the county ranking for single-family homes within ¼ mile and across the ZIP.
How
Percent of homes below this one on each measure; the tick is the typical (median) home. ZIP figures use exact percentiles over every home in the ZIP.
Limits
Only homes on the county record; condos and new builds may be missing.

AI summary and questions

Uses
The structured numbers already in your report.
How
A language model writes a plain-language summary and answers questions from those numbers only.
Limits
It can be wrong. It is not legal, insurance, lending, or real estate advice.

Known limits

What any report can and can't tell you, whatever the address.

  • A snapshot in time

    A report reflects each source as of the moment it was generated. Maps, records, and readings change after that.

  • Estimates are labeled

    First-floor height, stories, and Harvey depth at a home are estimates unless you enter your own numbers. Badges in the report say which is which.

  • Models undercount

    FEMA's Harvey model and insurance claims each miss many flooded homes, so counts are floors, not totals.

  • Lines on maps

    Zone lines, lot lines, and building outlines are digitized and can be off by several feet to tens of feet.

  • Draft is not effective

    The 2026 draft maps can change before adoption. Insurance rules follow today's effective FEMA map.

  • Sources can be late or down

    When a source is unavailable we show that instead of guessing, and retry.

A report is informational. Nothing from FloodMaps replaces a licensed survey, an elevation certificate, a flood zone determination, an appraisal, an inspection, an insurance quote, or legal advice. See our Disclaimers and Terms of Service.

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