Blanco River at San Marcos

Highest listed crest 43.10 ftFlood stage 18.0 ft8 crests since 2015

The Blanco River at San Marcos crested at major flood stage 2 times among the 8 crests the National Weather Service lists from 2015 to 2021. The highest, 43.10 ft on May 24, 2015, was major flooding, 25.10 feet above flood stage. 1 other gauge on the Blanco River crested above flood stage within a week of it, 1 at its own highest listed crest.

The gauge

Highest listed crest: 43.10 ft; May 24, 2015; 136,888 cubic feet per second
Flood stage: 18.0 ft; Major flooding from 30.0 ft
Crests at major: 2; 218th of 370 gauges in Texas
Most recent flood crest: October 14, 2021; 24.71 ft, moderate flooding
Location: Hays County; Near San Marcos (1.6 mi), Kyle (8.1 mi), Lockhart (13.7 mi)
Identifiers: NWS BSMT2; USGS 08171350

Flood stages

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

Flood categories, Blanco River at San Marcos

Action stage	13.0	2	Apr 11, 2017	The level at which the NWS or its partners begin to take action
Flood stage (minor)	18.0	1	May 4, 2019	Minimal or no property damage, but possibly some public threat
Moderate flood stage	24.0	2	Oct 14, 2021	Some inundation of structures and roads near the stream
Major flood stage	30.0	2	Oct 30, 2015	Extensive inundation of structures and roads

Every listed crest

8 crests from 2015 to 2021. 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, Blanco River at San Marcos

1	May 24, 2015	43.10	+25.10	Major	136,888
2	Oct 30, 2015	42.56	+24.56	Major	132,205
3	Oct 14, 2021	24.71	+6.71	Moderate	29,235
4	May 9, 2019	24.14	+6.14	Moderate	26,991
5	May 4, 2019	20.53	+2.53	Minor	13,690
6	Sep 26, 2016	15.23	−2.77	Action	3,430
7	Apr 11, 2017	13.49	−4.51	Action	2,660
8	Aug 27, 2017	10.93	−7.07	Below flood stage	1,040

The worst floods along the Blanco River

For this gauge's highest crests, the other gauges on the Blanco River that crested above flood stage within a week.

May 24, 2015: 43.10 ft here, major flooding

WimberleyTX · May 24, 2015 · 44.90 ft · Major · its highest

October 30, 2015: 42.56 ft here, major flooding

WimberleyTX · Oct 30, 2015 · 26.54 ft · Major

May 9, 2019: 24.14 ft here, moderate flooding

Fischer Store Rd near FischerTX · May 8, 2019 · 20.38 ft · Minor · its highest
BlancoTX · May 8, 2019 · 18.36 ft · Minor · its highest
WimberleyTX · May 9, 2019 · 14.57 ft · Minor
Crabapple RoadTX · May 8, 2019 · 7.01 ft · Minor · its highest

Gauges on the Blanco River

Flood gauges sharing the river's name, linked within 80 miles of one another.

Flood gauges on the Blanco River

Blanco	TX	18.0	18.36 ft, May 8, 2019	0
Crabapple Road	TX	7.0	7.01 ft, May 8, 2019	0
Fischer Store Rd near Fischer	TX	17.0	20.38 ft, May 8, 2019	0
San Marcos this gauge	TX	18.0	43.10 ft, May 24, 2015	2
Wimberley	TX	13.0	44.90 ft, May 24, 2015	6

Other gauges in Hays County

Flood gauges in Hays County

Fischer Store Rd near Fischer	17.0	20.38 ft, May 8, 2019	0
Wimberley	13.0	44.90 ft, May 24, 2015	6
Buda	15.0	23.39 ft, Oct 30, 2015	0
Driftwood	5.5	26.39 ft, Oct 30, 2015	11

Hays County: every hazard · River floods across the country · Texas

NOAA National Water Prediction Service, gauge BSMT2, 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.