How we show flood risk

We show FEMA’s official flood zones on the map. If your address sits in one, you can see it. The important part is what that does and does not mean, because it is the most misread number in a home search.

“Not in a flood zone” does not mean it will not flood

This is the one to take away. A FEMA flood zone marks where flooding is expected from a river, a lake, or the sea. It is drawn from the behaviour of a body of water.

It does not map the water that lands on your roof. Heavy rain that overwhelms storm drains floods streets and basements far outside any mapped zone. A large share of flood insurance claims come from properties that were never in one.

So read the layer as “this area floods from the river,” not as “this area is the only part that floods.”

What the zone letters mean

You will see a few codes. In plain terms:

• Zones A and AE — high risk. Flooding is expected here in a serious storm. If you have a federally-backed mortgage, insurance is normally required.
• Zone VE — high risk, coastal, with wave action on top of the water level. Treated more seriously than AE for good reason.
• Zone X — outside the high-risk area. Often described as “minimal risk,” which oversells it. It means lower risk, not no risk.

You can see these for any address on the flood map.

These maps age

FEMA redraws flood maps area by area, and some have not been revised in a long time. Meanwhile the ground changes. New roads and rooftops mean rain runs off instead of soaking in, so water arrives faster and in greater volume than it did when the map was drawn.

The practical effect is that an old map tends to understate risk in places that have been built up since. It rarely overstates it.

Why we show it anyway

Because it is the map your lender and your insurer will use. Whatever its flaws, it decides whether you are required to carry flood insurance and it affects what that costs. That makes it a real constraint on a budget, not just a risk estimate.

It is also the only flood layer with consistent national coverage. A patchwork of better local studies would not let you compare two metros.

What to do with it

Treat the zone as a starting question rather than an answer. If a place you like sits in or near a mapped zone, it is worth asking the seller or a local agent what has actually happened there. Ask about the last big storm. Ask whether the basement has ever taken water.

Local memory is often better than the map, and it is free to ask.

Where the data comes from

FEMA’s National Flood Hazard Layer, the same source used for official flood determinations. We show it as published. Where FEMA has not mapped an area at all, we leave it blank rather than guessing, because an unmapped area is genuinely unknown rather than safe.

Every page showing flood data carries the date we last checked it.

You can look up any address on the map. It is free, and it costs nothing to check before you fall in love with a house.