Squire Cheyney Farm · Photo: Smallbones · CC0FEMA expects less hazard damage per building in Thornbury Township than in 84% of U.S. towns, mostly from river and rain flooding
On FEMA’s National Risk Index, Thornbury Township gets an A− for hazard risk: lower expected damage per building than 84% of U.S. towns, #340 of 1,037 in Pennsylvania. Most of that expected damage is river and rain flooding (84%). Flood insurance has paid 12 claims here since 1999.
Graded on FEMA’s expected yearly building damage per dollar of building value (NRI v1.20, December 2025), weighted by where residents live; flood claims are shown, not graded. How hazard risk is graded
What Thornbury Township faces
Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.
River and rain flooding
Hurricanes
Shares are of FEMA’s expected building damage, the measure the grade uses; ranks compare each hazard’s building-damage rate with all 85,154 U.S. census tracts. In FEMA’s terms, river and rain flooding is FEMA’s “Inland Flooding” (rivers and streams overflowing their banks, or rain overwhelming drainage). FEMA defines coastal flooding as high or rising tides and storm surge, so surge damage is counted there. Drought isn’t listed: FEMA counts its losses in crops only.
What’s behind Thornbury Township’s grade
River and rain flooding is 84% of the building damage FEMA expects in Thornbury Township, and Thornbury Township’s rate of river and rain flooding damage is lower than 61% of U.S. census tracts. Next is hurricanes at 6% (higher than 67% of U.S. census tracts).
A− #340 of 1,037 in Pennsylvania; lower expected damage per building than 84% of U.S. towns (21,298).
All of Thornbury Township’s residents live in one census tract; the figures are that tract’s.
The typical Pennsylvania town has lower expected damage than 71% of U.S. towns; within the state, Thornbury Township has less expected damage per building than 67% of Pennsylvania towns.
In dollars, FEMA expects about $1.1M a year in losses across Thornbury Township: $939K to buildings, the rest to people and crops.
Does Thornbury Township flood? Sometimes: 12 flood claims since 1999
Every paid claim on a federal flood insurance policy in Thornbury Township, from FEMA’s records: 10.3 per 1,000 homes, more than 74% of the 13,809 U.S. towns with a flood insurance record.
- Hurricane Floyd3 claims · $99K
- Hurricane Irene2 claims · $6K
Thornbury Township isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Chester County.The storms Thornbury Township remembers
None of the 21 disasters declared for Chester County shows FEMA aid or repair money reaching Thornbury Township itself in FEMA’s records, so these are its biggest flood-claim years.
- 19994 flood claims paidThe year of Hurricane Floyd Major Disaster Declarations, declared for Chester County
- 20114 flood claims paidThe year of Tropical Storm Lee, declared for Chester County
- 20043 flood claims paidThe year of Tropical Depression Ivan, declared for Chester County
Chester County has had 21 natural disasters declared by the President since 1953, most often severe storms, then hurricanes and tropical storms. Not counted: the 2005 Hurricane Katrina evacuee emergency, which covered counties that took in evacuees.
Old photos of Thornbury Township after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the Thornbury Township archive →Thornbury Township and its neighbors
Thornbury Township is 3rd of the 4 graded towns here, from least expected damage per building to most. Tap a town to see its hazards.
| Town | Hazard risk | Mostly (buildings) | Flood claims |
|---|---|---|---|
| Westtown Township | Aless damage than 94% | river and rain flooding | 5 |
| Thornbury Township | Aless damage than 93% | river and rain flooding | — |
| Thornbury Township | A−less damage than 84% | river and rain flooding | 12 |
| Birmingham Township | A−less damage than 77% | river and rain flooding | 10 |
| Dilworthtown | — | a Census area inside a town; graded with the town | |
| Cheyney University | — | 308 residents; we grade 1,000+ | |
Hazard risk = FEMA’s expected yearly building damage per dollar of building value, vs. the 21,298 U.S. towns we grade; the map is shaded by fifths of the same scale. Flood claims = paid federal flood insurance claims on record.
Get ready for what Thornbury Township faces
A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.
- Turn around at flooded roads: a foot of moving water can carry off a car.
- Flood insurance usually takes 30 days to start, so buy it before the forecast.
- Keep papers and medicines up high, in a grab-and-go bag.
- The season runs June through November and peaks from mid-August to mid-October.
- Bring in porch furniture and anything the wind can throw.
- Fill the gas tank and charge phones before the storm arrives.
- Look up the address on FEMA’s flood map.
- Ask the seller or landlord whether it has ever flooded, and what flood insurance costs there.
- Get a flood insurance quote early: policies usually start 30 days after you buy.
Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.
Questions about natural hazards in Thornbury Township
Is Thornbury Township at risk for natural disasters?
On FEMA’s National Risk Index, Thornbury Township has lower expected damage per building than 84% of U.S. towns: A− for hazard risk, #340 of 1,037 in Pennsylvania. Most of the expected damage is river and rain flooding (84%) and hurricanes (6%). The figures are for the one census tract the town shares with its neighbors. This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does Thornbury Township flood?
Flood insurance has paid 12 claims in Thornbury Township since 1999, $219K in all, or 10.3 per 1,000 homes, more than 74% of U.S. towns with a flood insurance record. 2 properties have flooded more than once. The most claims came from Hurricane Floyd (3).
Is Thornbury Township in a flood zone?
Flood zones are drawn street by street, so the answer depends on the address: look it up on FEMA’s flood map. In Chester County, 40% of homes in mapped flood zones carry federal flood insurance, and 0.6% of all homes do.
How much is flood insurance in Thornbury Township?
FEMA’s Community Rating System list shows no discount for Thornbury Township’s flood program. Premiums depend on the building; policies usually start 30 days after you buy, so get a quote early.
What was the biggest storm in Thornbury Township?
By flood claims, Hurricane Floyd: 3 paid, $99K.
Is Thornbury Township at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (84%), and Thornbury Township’s rate for it is lower than 61% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Thornbury Township.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Thornbury Township’s residents lived in the 2020 census; OpenFEMA: NFIP redacted claims, multiple-loss properties, community status book and residential penetration rates, housing assistance (owners and renters), public assistance funded projects, hazard mitigation properties and disaster declarations. Homes: Census ACS 2020–24. Preparedness tips: Ready.gov. FEMA’s model is an average of expected damage, not a forecast. How hazard risk is graded.