Pilarcitos Creek at Half Moon Bay

Highest listed crest 13.08 ftFlood stage 9.1 ft2 crests since 1982

The Pilarcitos Creek at Half Moon Bay crested above flood stage 2 times among the 2 crests the National Weather Service lists from 1982 to 1998. The highest, 13.08 ft on January 4, 1982, was minor flooding, 3.98 feet above flood stage.

The gauge

Highest listed crest: 13.08 ft; January 4, 1982; 4,750 cubic feet per second
Flood stage: 9.1 ft; Major flooding from 24.0 ft
Crests at major: 0; 2 above flood stage
Most recent flood crest: February 3, 1998; 12.27 ft, minor flooding
Location: San Mateo County; Near Half Moon Bay (0.3 mi), Hillsborough (7.5 mi), Belmont (8.3 mi)
Identifiers: NWS HMNC1; USGS 11162630; out of service

Flood stages

The thresholds the National Weather Service uses for this gauge today, and how many listed crests reached each.

Flood categories, Pilarcitos Creek at Half Moon Bay

Action stage	7.5	0	—	The level at which the NWS or its partners begin to take action
Flood stage (minor)	9.1	2	Feb 3, 1998	Minimal or no property damage, but possibly some public threat
Moderate flood stage	17.0	0	—	Some inundation of structures and roads near the stream
Major flood stage	24.0	0	—	Extensive inundation of structures and roads

Every listed crest

2 crests from 1982 to 1998. Filled: at or above flood stage. Hover a crest for its date and stage.

Crests at or above flood stage, by decade

These are the crests the local National Weather Service office lists for the gauge: the highest on record and recent crests. Lesser floods between them may be missing, so counts by decade are a floor.
Categories use today's flood stages. Levees, dams and channel changes since a crest can make old and new stages not directly comparable.

Highest crests

Highest listed crests, Pilarcitos Creek at Half Moon Bay

1	Jan 4, 1982	13.08	+3.98	Minor	4,750
2	Feb 3, 1998	12.27	+3.17	Minor	1,950

San Mateo County: every hazard · River floods across the country · California

NOAA National Water Prediction Service, gauge HMNC1, retrieved October 30, 2026. Stages in feet on the gauge's own datum, not elevation. Crests are as the National Weather Service lists them; preliminary values may be revised.