Photo: Thebluewriter · CC BY-SA 4.0On FEMA’s figures, Diamond Bar faces more hazard damage per building than 90% of U.S. towns, mostly from earthquakes
On FEMA’s National Risk Index, Diamond Bar gets a D for hazard risk: higher expected damage per building than 90% of U.S. towns, #344 of 847 in California. Most of that expected damage is earthquakes (51%), then river and rain flooding (45%). Flood insurance has paid 1 claim here since 1998.
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 Diamond Bar faces
Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.
Earthquakes
River and rain flooding
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 Diamond Bar’s grade
Earthquakes are 51% of the building damage FEMA expects in Diamond Bar, and Diamond Bar’s rate of earthquakes damage is in the top 7% of U.S. census tracts. Wildfire adds 4%, at a rate in the top 5% of U.S. census tracts.
D #344 of 847 in California; higher expected damage per building than 90% of U.S. towns (21,298).
Diamond Bar’s residents live in 13 census tracts; FEMA’s figures are combined by where they live.
The typical California town has higher expected damage than 92% of U.S. towns; within the state, Diamond Bar has less expected damage per building than 59% of California towns.
In dollars, FEMA expects about $43.5M a year in losses across Diamond Bar: $39.2M to buildings, the rest to people and crops.
Does Diamond Bar flood? Rarely: 1 flood claim since 1998
Every paid claim on a federal flood insurance policy in Diamond Bar, from FEMA’s records: 0.1 per 1,000 homes, fewer than 100% of the 13,809 U.S. towns with a flood insurance record.
- The Pineapple Express - Southern1 claim · $7K
Diamond Bar isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Los Angeles County.4 federal disasters brought FEMA money to Diamond Bar
Disasters that paid out in Diamond Bar itself (aid to households or repair grants to the City of Diamond Bar), newest first, with that year’s flood claims.
- 2025Wildfires and Straight-line Winds77 households applied for aid$20K aid approved
- 2017Severe Winter Storms, Flooding, and Mudslides$945K to the City of Diamond Bar for repairs
- 2010Severe Winter Storms, Flooding, and Debris and Mud Flows$13K to the City of Diamond Bar for repairs
- 2004Severe Storms, Flooding, Debris Flows, and Mudslides25 households applied for aid$56K aid approved$55K to the City of Diamond Bar for repairs
Los Angeles County has had 40 natural disasters declared by the President since 1953, most often severe storms, then floods. Not counted: the 2005 Hurricane Katrina evacuee emergency, which covered counties that took in evacuees.
Also 44 FEMA wildfire suppression grants (Fire Management Assistance, not a disaster declaration) for fires in Los Angeles County, 2002–2025.
Old photos of Diamond Bar after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the Diamond Bar archive →Diamond Bar and its neighbors
Diamond Bar has the lowest expected damage per building of the 4 graded towns here. Tap a town to see its hazards.
| Town | Hazard risk | Mostly (buildings) | Flood claims |
|---|---|---|---|
| Diamond Bar | Dmore damage than 90% | earthquakes | 1 |
| Rowland Heights | Dmore damage than 92% | river and rain flooding | 2 |
| Pomona | D−more damage than 97% | river and rain flooding | 5 |
| Chino Hills | D−more damage than 98% | river and rain flooding | 1 |
| Industry | — | 210 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 Diamond Bar faces
A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.
- Drop, cover and hold on.
- Strap tall furniture and the water heater to the wall.
- Know how to shut off the gas.
- 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.
- 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 Diamond Bar
Is Diamond Bar at risk for natural disasters?
On FEMA’s National Risk Index, Diamond Bar has higher expected damage per building than 90% of U.S. towns: D for hazard risk, #344 of 847 in California. Most of the expected damage is earthquakes (51%) and river and rain flooding (45%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does Diamond Bar flood?
Flood insurance has paid 1 claim in Diamond Bar since 1998, $7K in all, or 0.1 per 1,000 homes, fewer than 100% of U.S. towns with a flood insurance record. The most claims came from Pineapple Express - Southern (1).
Is Diamond Bar 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 Los Angeles County, 33% of homes in mapped flood zones carry federal flood insurance, and 0.5% of all homes do.
How much is flood insurance in Diamond Bar?
FEMA’s Community Rating System list shows no discount for Diamond Bar’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 Diamond Bar?
By FEMA money that reached Diamond Bar, Severe Winter Storms, Flooding, and Mudslides (2017): $945K to the City of Diamond Bar for repairs. By flood claims, Pineapple Express - Southern: 1 paid, $7K.
Is Diamond Bar at risk from earthquakes?
It is the largest share of the building damage FEMA expects here (51%), and Diamond Bar’s rate for it is in the top 7% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Diamond Bar.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Diamond Bar’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.