Debris Flow in the United States

How dangerous are Debris Flow events in the U.S.?

The loss ranking is the stronger warning against reading frequency alone. Debris Flow is #29 of 54 by event count but rises to #12 for combined property and crop damage. Its losses make up 0.4% of the catalog total, while its fatalities rank #24 and represent 0.6% of recorded deaths. Fewer events can still produce an outsized financial record.

Annual totals swing noticeably from year to year. The peak year on record was 2021, logging 212 events and $164.4M in property damage in a single calendar year. The most recent year in the dataset is 2025 with 163 events recorded. Across the full 11-year window, annual event counts reflect seasonal climate cycles and, for some years, longer climate-driven shifts in frequency.

Per event, this hazard is far more dangerous than its frequency suggests. It ranks #29 by how often it is recorded among the 44 hazard types with at least 100 events, but #14 by fatalities per event, at 38.8 deaths per 1,000 recorded events. Recorded damage averages $600.1K per event. A reader scanning total counts would underestimate the risk of encountering one.

Geographic exposure skews toward a small cluster of frequently-hit states. The three states absorbing the largest share of events are California (621 events, 27 fatalities), Puerto Rico (297 events, 0 fatalities), Colorado (218 events, 0 fatalities), a mix of underlying hazard climatology and how many people live in the exposed corridor. At the other end, states such as Wisconsin, U.S. Virgin Islands, Guam report far fewer events, a meaningfully lower-frequency pattern there, though local vigilance still matters.

The NOAA file shows a substantial human toll without entering PlainHazard's highest band: 62 fatalities and 185 injuries across 1,600 events. The high band covers hazard types with 20-99 cumulative fatalities in this 2015-2025 record. It compares catalog totals only; exposure and consequences vary widely from one event and location to another.

NOAA entries are reports filed by local National Weather Service offices. Counts therefore reflect both observed weather and reporting practice; they do not measure unreported events, household exposure, or the probability of a future event at one address.