Debris Flow
NOAA Storm Events type · 2,545 records since 1996 · 40 states and territories
The National Weather Service defines debris flow as: "A slurry of loose soil, rock, organic matter, and water, similar to wet concrete, which is capable of holding particles larger than gravel in suspension." NOAA's Storm Events Database holds 2,545 debris flow records from 1996 through June 30, 2026, the most in California (767), with 153 deaths recorded.
How the National Weather Service files debris flow
A slurry of loose soil, rock, organic matter, and water, similar to wet concrete, which is capable of holding particles larger than gravel in suspension. They can mobilize from landslides on steep, nearly saturated slopes or be triggered by intense rain after wildfires.
National Weather Service Instruction 10-1605, Storm Data Preparation (July 26, 2021), Appendix A, entry 6
Source: National Weather Service Instruction 10-1605. Read the instruction (PDF).
Debris Flow, 1996 to 2026
Records per year (2026 to June 30, 2026).
- recorded, no damage figure
- under $10 million
- $10 million or more
- $100 million or more
- $1 billion or more, or 100 deaths
- $10 billion or more, or 1,000 deaths
- a year's colour: its recorded damage or deaths
- a year with a death
- Records
- 2,5451996 to June 30, 2026
- Deaths
- 153253 injuries
- Damage, 2025 dollars
- $1.7Bas filed (scale steps before 1993)
- Counties with a record
- 439of 3,266
Source: NOAA NCEI Storm Events Database, records through June 30, 2026. Search the record at NCEI.
Where do debris flow records happen?
States
Counties
Source: NOAA NCEI Storm Events Database (forecast-zone records count on every county the zone covers).
When do debris flow records happen?
The busiest month is August.
The values, month by month
Jan 276 · Feb 287 · Mar 175 · Apr 207 · May 218 · Jun 118 · Jul 291 · Aug 316 · Sep 174 · Oct 164 · Nov 139 · Dec 180 (records).
Source: NOAA NCEI Storm Events Database, records by the month they began.
The deadliest debris flow records
| Date | Record | Character | Killed | Injured | Damage |
|---|---|---|---|---|---|
| 2014-03-22 | Debris FlowOso, Snohomish County, WA On a warm and dry 22nd of March, 2014, a large landslide occurred four miles east of the town of Oso, Washington. The slide debris, traveling at over 60 miles per hour, crossed the entire river valley, covering an area of over a square mile with an approximate deposit thickness of 15 to 75 feet in some areas. The ... | 43 | 12 | $75M | |
| 2018-01-09 | Debris FlowSummerland, Santa Barbara County, CA Intense rainfall generated a large and deadly mud and debris flow in the community of Montecito, around the burn scar of the Thomas fire. Automated rain gauges in the area indicated very intense rainfall, reaching as high as 0.54 inches in 5 minutes. The intense rainfall resulted in a mud and debris estimated to be 15 ... | 21 | 168 | $725M | |
| 2003-12-25 | Debris FlowSan Bernardino County, CA · forecast zone San Bernardino County Mountains Steady light to moderate rain began falling over the burned areas of the San Bernardino Mountains on 0600 PST 12/24/03. Approximately 24 hours later, mud, rock, and debris flows were being reported along highways and roads leading into the mountain resort communities. By 0800 PST on Christmas Day, more than two inches ... | 14 | 10 | $8.0M | |
| 2024-09-27 | Debris FlowBlue Ridge, Buncombe County, NC A large debris flow developed along Old Fort Rd in the Fairview area, destroying multiple homes and killing 11 members of the same family. A second large debris flow later developed and killed two emergency workers responding to the first event. | 13 | 0 | $941K | |
| 2005-01-10 | Debris FlowSanta Barbara County, CA · forecast zone Santa Barbara County South Coast A powerful Pacific storm brought heavy rain, snow, flash flooding, high winds and landslides to Central and Southern California. During the 5 day event, rainfall totals ranged from 3 to 10 inches over coastal areas with up to 32 inches in the mountains. With such copious rainfall, flash flooding was a serious problem ... | 10 | 0 | – | |
| 2023-11-20 | Debris FlowWrangell, AK By the early evening as the front was moving eastward a landslide was reported near mile post 11 south of Wrangell along the Zimovia Highway, which blocked the road and cut power to residents on the other side of the slide. The landslide resulted in 6 people perishing and 3 homes being destroyed, one person survived ... | 6 | 1 | $1.5M | |
| 2004-09-16 | Debris FlowMacon County, NC · forecast zone Macon A landslide (debris flow) began at the top of Fishhawk Mountain and flowed through the Peeks Creek valley. The slide, consisting of water, boulders, trees, mud, and other debris, destroyed or severely damaged 20 to 30 homes and mobile homes. Four people and an unborn child were killed as their homes were overwhelmed ... | 4 | 9 | $2.5M | |
| 1997-01-19 | Debris FlowJefferson County and 2 more, WA · forecast zone Hood Canal/Kitsap Peninsula A mudslide kills a family of four while they were sleeping in their home. The house, on Bainbridge Island, slid down a hill into Puget Sound. 20 other homes in the vicinity were evacuated. Two days before the slide, the nearby city of Hoodsport received 2.91 inches of rain in 24 hours. | 4 | 0 | – |
Source: NOAA NCEI Storm Events Database, deaths direct and indirect as filed.
The most recent debris flow records
| Date | Record | Character | Killed | Injured | Damage |
|---|---|---|---|---|---|
| 2026-06-26 | Debris FlowJemez Spgs, Sandoval County, NM | 0 | 0 | $50K | |
| 2026-05-29 | Debris FlowEddy, Sanders County, MT | 0 | 0 | – | |
| 2026-05-16 | Debris FlowAguadilla Municipio, PR | 0 | 0 | $2K | |
| 2026-04-28 | Debris FlowComerio, Comerío Municipio, PR | 0 | 0 | $1K | |
| 2026-04-28 | Debris FlowBarceloneta Municipio, PR | 0 | 0 | $1K | |
| 2026-04-28 | Debris FlowComerio, Comerío Municipio, PR | 0 | 0 | $2K | |
| 2026-04-28 | Debris FlowVega Baja Municipio, PR | 0 | 0 | $2K | |
| 2026-04-27 | Debris FlowNaranjito Municipio, PR | 0 | 0 | $2K |
Source: NOAA NCEI Storm Events Database.