Ranking · counties
The 25 US counties with the most flood-prone soil
In St. Bernard Parish, LA, 92% of the land is mapped as flooding frequently, the most of any county. 15 of the 25 counties on this list are Louisiana parishes.
- Top county
- 92%
- floods frequently · St. Bernard Parish, LA
- Top state
- 32%
- floods occasionally or often · Louisiana
- Louisiana parishes
- 15 of 25
- on the county list
Counties where soil floods most often
Share of land that floods frequently
| County | Floods frequently | Occasionally | Never or rarely |
|---|---|---|---|
| 1. St. Bernard Parish, LA | 92% | 0% | 8% |
| 2. Plaquemines Parish, LA | 82% | 0% | 18% |
| 3. Cameron Parish, LA | 80% | 1% | 14% |
| 4. Terrebonne Parish, LA | 80% | 7% | 10% |
| 5. St. Charles Parish, LA | 74% | 0% | 24% |
| 6. St. John the Baptist Parish, LA | 74% | 0% | 25% |
| 7. Lafourche Parish, LA | 72% | 3% | 25% |
| 8. Issaquena County, MS | 64% | 5% | 30% |
| 9. St. Martin Parish, LA | 62% | 3% | 34% |
| 10. St. Mary Parish, LA | 60% | 5% | 31% |
| 11. Assumption Parish, LA | 60% | <1% | 40% |
| 12. Jefferson Parish, LA | 58% | <1% | 42% |
| 13. St. James Parish, LA | 56% | 0% | 41% |
| 14. Iberia Parish, LA | 55% | 3% | 41% |
| 15. Iberville Parish, LA | 49% | 4% | 44% |
| 16. Glynn County, GA | 49% | 11% | 40% |
| 17. Bryan County, GA | 49% | <1% | 51% |
| 18. Lanier County, GA | 48% | 0% | 52% |
| 19. Camden County, GA | 48% | 9% | 44% |
| 20. Broward County, FL | 45% | 0% | 46% |
| 21. Sharkey County, MS | 44% | 10% | 46% |
| 22. McIntosh County, GA | 44% | 5% | 50% |
| 23. Lake County, TN | 44% | 19% | 35% |
| 24. Berrien County, GA | 43% | 0% | 57% |
| 25. Vermilion Parish, LA | 42% | 1% | 56% |
States with the most flood-prone soil
| State | Occasionally or frequently | Frequently |
|---|---|---|
| 1. Louisiana | 32% | 26% |
| 2. Mississippi | 27% | 12% |
| 3. Georgia | 17% | 13% |
| 4. Alabama | 17% | 12% |
| 5. Missouri | 16% | 6% |
| 6. New Jersey | 16% | 13% |
| 7. Florida | 15% | 13% |
| 8. Tennessee | 14% | 5% |
| 9. South Carolina | 13% | 11% |
| 10. Arkansas | 13% | 9% |
Soil flooding is not the same as a flood zone
Soil scientists class flooding by how often a soil is covered by flowing water from rivers or the sea: frequent means more than once in two years on average, occasional means once in 2 to 20 years, rare once in 20 to 100 years. They read it from the soil itself, from layers of river sediment and the landscape, not from a flood model.
That makes it a useful second opinion next to FEMA flood maps, but not a replacement: a levee, a dam or new development can change how often land floods. For a specific property, check the FEMA flood map and the lot's elevation.
Sources & data dates
- Source
- USDA NRCS Soil Survey Geographic Database (SSURGO), queried through Soil Data Access. Public domain.
- Data date
- SSURGO as published on November 3, 2026 (most recent survey area update October 26, 2026). NRCS refreshes SSURGO each October.
- Scope
- All mapped land in the 50 states and DC in the current soil survey.
- Method
- County rankings include counties with at least 100,000 acres of mapped land and soil ratings on at least 80% of it, so a small county with one unusual map unit cannot top the list. Counties without a full report on this site are named but not linked; the ZIP lookup covers them. Flooding is the most frequent monthly flooding class of each soil component, weighted by area. Ponding (standing water from rain) is not counted. Full methodology.