Short answer
In a 120-point sample of FEMA's National Flood Hazard Layer inside Anderson city limits, about 8% of land fell in a Special Flood Hazard Area, including about 6% in the regulatory floodway, and about 91% was mapped as minimal flood hazard. Flood zones matter for insurance and building rules. Most basement leaks in Anderson come from groundwater, inside and outside flood zones.
What the FEMA maps show inside the city
We checked FEMA’s National Flood Hazard Layer at 120 random points inside Anderson’s Census city boundary in October 2026.
| FEMA zone | Share of sampled points | What it means |
|---|---|---|
| Zone X, minimal flood hazard | about 91% | Outside the mapped 1%-annual-chance floodplain |
| Zone AE, Special Flood Hazard Area | about 8% | Inside the mapped 1%-annual-chance floodplain |
| of which: regulatory floodway | about 6% | The channel and nearby land kept clear to carry floodwater |
| Zone X, reduced risk due to levee | 1 point | Protected by a levee, with residual risk |
Source: FEMA National Flood Hazard Layer, sampled October 2026. Shares describe land area, not homes.
The mapped hazard areas follow the White River and its creeks. The soil survey agrees in broad terms: only a few percent of sampled city land has soils mapped as subject to flooding (USDA NRCS).
Look up your address
- Go to FEMA’s Flood Map Service Center (msc.fema.gov) and search your address.
- Note the zone and whether a floodway is nearby.
- If you’re close to a zone boundary, an elevation certificate tells you how your house sits relative to the base flood elevation.
Reading the zone labels
- Zone AE: inside the mapped 1%-annual-chance floodplain, with a base flood elevation shown on the map.
- Floodway: the part of zone AE that carries the main flow. Building there faces the strictest limits.
- Zone X (shaded): the 0.2%-annual-chance floodplain, or areas protected by a levee.
- Zone X (unshaded): minimal flood hazard.
“1%-annual-chance” means a flood that has a 1 in 100 chance of being reached or exceeded in any year. Over a 30-year mortgage, that adds up to a real chance. The maps are drawn from models and past floods, so a record flood can go beyond them. Our data and methods page explains how we sampled the maps.
What a flood zone means
- Insurance. Lenders typically require flood insurance for mortgaged homes in a Special Flood Hazard Area. Homeowners policies exclude flood damage.
- Building rules. New construction and substantial improvements in a flood zone face elevation and permitting requirements. Check with the city or county before major basement work in a mapped zone.
- Basements. In a flood zone, river water can reach the house over the ground during big floods. That’s a different problem from seepage, with different preparation. See White River flooding.
Flood zone or not, the usual Anderson problem is groundwater
With about 91% of sampled city land outside mapped flood zones, most wet basements here are dealing with water in the soil, not river water. On Anderson’s till soils, the soil survey estimates a seasonal water table near the surface across much of the city. That’s why the common fixes are drainage at the footing and a reliable sump pump. See the water table and soils.
If you’re in a mapped flood zone
- Price flood insurance even if your lender doesn’t require it.
- Keep the furnace, water heater and valuables off the basement floor, or move them up.
- Make sure downspouts and the sump discharge carry water away from the house.
- Know your evacuation route and how to shut off utilities.
- Install a backwater valve if your home is on a combined sewer. See combined sewers and backups.
If water is in your basement right now, start with the first-hour checklist.