New Hampshire inland flooding risk
Hillsborough County has the highest inland flooding risk in New Hampshire, scoring 92.6 out of 100 — rated "Relatively Moderate" by FEMA's National Risk Index. Recorded inland flooding events across New Hampshire have increased 84% over the past five years compared to the prior five-year period.
| # | County | NRI score | Rating |
NOAA events 2016–2026 |
|---|---|---|---|---|
| 1 | Hillsborough County | 92.6 | Relatively Moderate | 52 |
| 2 | Grafton County | 90.1 | Relatively Moderate | 106 |
| 3 | Rockingham County | 89.1 | Relatively Moderate | 9 |
| 4 | Merrimack County | 85.8 | Relatively Moderate | 40 |
| 5 | Carroll County | 82 | Relatively Moderate | 46 |
| 6 | Coos County | 77.6 | Relatively Moderate | 55 |
| 7 | Strafford County | 76 | Relatively Moderate | 6 |
| 8 | Cheshire County | 74.8 | Relatively Moderate | 47 |
| 9 | Belknap County | 70.3 | Relatively Low | 13 |
| 10 | Sullivan County | 60.6 | Relatively Low | 28 |
Source: FEMA National Risk Index v1.20.0, December 2025. Scores are 0–100 percentile rankings among all US counties. See the methodology page for definitions. Download the full CSV for all counties.
Inland Flooding risk nationally:
Other hazard risks in New Hampshire:
Frequently asked questions
What is the highest inland flooding risk county in New Hampshire?
Hillsborough County, NH has the highest inland flooding risk in New Hampshire, with a FEMA National Risk Index score of 92.6 out of 100 (rated "Relatively Moderate").
What causes inland flooding risk in New Hampshire?
Inland flooding covers riverine and surface (pluvial) flooding — the most common and costly natural disaster type in the US. High scores appear across river floodplains in the Midwest, South, and Mid-Atlantic, where legacy development in flood-prone areas and aging stormwater infrastructure concentrate risk.