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, what does the land around it do when it rains, and what soil and sunlight does it have.

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 address flooded? 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 →
Bar chart of FEMA flood insurance claims per 1,000 homes since 1978 in the 20 highest of the 50 largest U.S. cities, led by Houston, Tampa, Virginia Beach and Miami.

Data

Flood claims in the 50 largest cities All 50 ranked by FEMA flood insurance claims per 1,000 homes, with each city’s biggest flood year. Read the guide →
Map of the lower 48 states colored by average daily sunlight, from about 3 kWh per square meter in the cloudy Pacific Northwest to over 6 in the desert Southwest.

Sun & solar

How much sun does my property get? Average sunlight for any U.S. address, how a south or north slope changes it, and what the map can’t see. Read the guide →
Map of the lower 48 states colored by most likely soil type: Luvisols across the Midwest and South, Kastanozems and Chernozems on the Plains, Acrisols in the Southeast, Calcisols in the desert Southwest.

Soil

What soil type is my property? Sand or clay, what that means for drainage, and how to look up the soil under any U.S. address. Read the guide →
Diagram: how often a hazard happens, what is in its way, and how much damage past events did give the expected yearly loss; a community risk factor adjusts it; the result is ranked against every U.S. census tract into five ratings from Very Low to Very High.

Natural hazards

What a FEMA risk rating means How the National Risk Index rates an area, why the same place gets different answers, and the limits of any single risk score. 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.