What is FloodSight?

FloodSight is a free, no-login web application that aggregates official U.S. government flood and weather data into a single, easy-to-use map interface. It was built to solve a simple problem: most people do not know their flood risk, and finding that information typically requires navigating multiple government portals with steep learning curves.

With FloodSight, you simply open the app, search for any U.S. address, and tap the map. In seconds you can see the official FEMA flood zone classification, the ground elevation at that point, any active National Weather Service flood alerts, and real-time river gauge readings from nearby USGS monitoring stations. FloodSight works on any modern smartphone or desktop browser, and can be installed as a Progressive Web App (PWA) on iOS and Android for offline access.

Who Is FloodSight For?

• Homebuyers and renters — Before signing a lease or making an offer, check whether the property sits inside a FEMA Special Flood Hazard Area (SFHA). Properties in high-risk zones often require mandatory flood insurance, which can add hundreds or thousands of dollars to annual costs.
• Current homeowners — Even if you have lived in a home for years, FEMA flood maps are periodically updated. A remapping study could change your zone designation and affect your insurance requirements or premium.
• Emergency preparedness planners — During active storm events, FloodSight's combination of live radar, NWS alerts, and real-time gauge readings gives a comprehensive picture of developing flood conditions.
• Outdoor enthusiasts — Hikers, campers, and paddlers can check stream gauge levels before heading into river corridors or flood-prone terrain.
• Local journalists and community advocates — FloodSight makes it easy to quickly assess flood risk for any location when reporting on storm impacts or advocating for infrastructure improvements.

Key Features

Understanding FEMA Flood Zones

FEMA's National Flood Insurance Program (NFIP) uses a series of zone designations to communicate flood risk. These zones appear on Flood Insurance Rate Maps (FIRMs) and determine insurance requirements for federally backed mortgages.

Zone	Risk Level	Description
A / AE	High Risk	1% annual chance flood (100-year flood). Mandatory flood insurance for federally backed mortgages. Zone AE includes Base Flood Elevations; Zone A does not.
AH / AO	High Risk	Shallow flooding zones — AH for ponding, AO for sheet flow. Depths typically 1–3 feet.
V / VE	Coastal High Hazard	Subject to storm surge AND wave action. Highest risk coastal areas. VE includes BFEs; V does not.
X (Shaded)	Moderate Risk	0.2% annual chance flood (500-year flood). Flood insurance is not mandatory but is often recommended.
X (Unshaded)	Minimal Risk	Outside the 0.2% annual chance floodplain. Lowest regulated flood risk.

Important: Being outside a high-risk flood zone does not mean a property is immune to flooding. FEMA estimates that approximately 25% of flood insurance claims come from properties outside high-risk zones. Flooding can occur from heavy rain, drainage problems, and rapid snowmelt — not just rivers and coastlines.

Understanding River Gauge Stages

USGS river gauges measure stream height (stage) continuously. The National Weather Service assigns action levels to each gauge based on local conditions:

• Normal: Water level is within the expected range. No threat to structures or roads.
• Action Stage: Water is approaching the top of the banks. Residents and emergency managers should begin monitoring closely.
• Minor Flood Stage: Water begins to overflow riverbanks. Low-lying roads, parks, and fields may be affected.
• Moderate Flood Stage: Significant flooding. Some residential or commercial structures may be impacted; road closures are likely.
• Major Flood Stage: Severe, life-threatening flooding. Extensive property damage and evacuations are expected.

Data Sources & Transparency

FloodSight does not collect, store, or sell any user data. All flood hazard data is retrieved directly from official U.S. government APIs in real time:

Source	Data Provided
FEMA / NFHL	Official flood zone boundaries and Base Flood Elevations
USGS Water Services	Real-time river gauge readings and stream network geometry
NOAA / NWS	Active flood alerts, watches, and advisories
NOAA / NEXRAD	Live precipitation radar imagery
NOAA Tides & Currents	Tide station predictions for coastal locations
USFWS	National Wetlands Inventory layer
USGS 3D Elevation	Ground elevation at any queried point
ArcGIS / Nominatim	Address geocoding and search

Privacy & Advertising

FloodSight is free to use and supported by Google AdSense advertising. We display contextually relevant ads to help cover server and API costs. Your location data is processed locally on your device and is never transmitted to FloodSight's servers. For full details on how your data is handled, see our Privacy Policy.