Guides

Check a property before you buy

Plain-English guides to the questions buyers ask most: has this house flooded, what does its flood zone really mean, and what does the land around it do when it rains.

Bar chart of FEMA flood insurance claims per year in Horry County, South Carolina, with spikes labeled Hurricane Hugo, Floyd, the October 2015 floods, Matthew, Florence and Ian.

Flood history

Has this house flooded before? What anyone can look up, what only the seller can get, and what the land itself tells you about past flooding. Read the guide →
Cross-section: FEMA flood zones follow the river, while a house in Zone X sits in a low spot where local runoff collects.

Flood zones

Is my house in a flood zone? How to look up a FEMA flood zone, what each zone means, and why Zone X can still flood. Read the guide →
Cross-section of a hillside: a ridge lot sheds water, a mid-slope lot has uphill water passing through, a low lot collects it.

Before you buy

Terrain checklist before buying land Ten checks for drainage, low spots, grading, slope, soils and wetlands, with free tools for each. Read the guide →
The same invented landscape drawn as a 3D block and as a contour map from above, with a hilltop, a valley, a ridge and a low spot marked A to D.

Map basics

How to read a drainage map Contour lines, high and low ground, and how to read Terreflow’s Surface Drainage view, including what it can’t tell you. Read the guide →

Looking at a specific area?

Look up the FEMA flood zone for any address for free, browse county flood & drainage maps, or analyze a U.S. address to see its terrain drainage next to the official FEMA flood zone.