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St. Marys River at Great Mills

Highest listed crest 13.34 ftFlood stage 7.0 ft74 crests since 1947

The St. Marys River at Great Mills crested at major flood stage 14 times among the 74 crests the National Weather Service lists from 1947 to 2024. The highest, 13.34 ft on August 20, 1969, was major flooding, 6.34 feet above flood stage.

The gauge

Highest listed crest
13.34 ft
August 20, 1969; 7,950 cubic feet per second
Flood stage
7.0 ft
Major flooding from 10.0 ft
Crests at major
14
3rd of 108 gauges in Maryland
Most recent flood crest
January 10, 2024
7.72 ft, minor flooding
Location
St. Mary's County
Maryland

Flood stages

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

Flood categories, St. Marys River at Great Mills
Action stage5.027Dec 16, 2022The level at which the NWS or its partners begin to take action
Flood stage (minor)7.018Jan 10, 2024Minimal or no property damage, but possibly some public threat
Moderate flood stage8.015Dec 18, 2023Some inundation of structures and roads near the stream
Major flood stage10.014Aug 4, 2020Extensive inundation of structures and roads

Every listed crest

74 crests from 1947 to 2024. Filled: at or above flood stage. Hover a crest for its date and stage.

Listed crests at the St. Marys River at Great Mills, 1947 to 2024 468101214ft Flood stage 7.0 ftMajor 10.0 ft Apr 16, 1947: 5.73 ft, action stage; 420 cubic feet per secondAug 4, 1948: 9.32 ft, moderate flooding; 1,560 cubic feet per secondJul 16, 1949: 9.91 ft, moderate flooding; 2,020 cubic feet per secondOct 31, 1949: 7.67 ft, minor flooding; 659 cubic feet per secondAug 8, 1951: 6.63 ft, action stage; 520 cubic feet per secondJan 29, 1952: 7.44 ft, minor flooding; 620 cubic feet per secondAug 14, 1953: 7.68 ft, minor flooding; 656 cubic feet per secondAug 13, 1955: 11.77 ft, major flooding; 4,350 cubic feet per secondNov 2, 1956: 10.66 ft, major flooding; 2,780 cubic feet per secondAug 25, 1958: 10.87 ft, major flooding; 3,030 cubic feet per secondJul 15, 1959: 7.09 ft, minor flooding; 580 cubic feet per secondJul 30, 1960: 12.08 ft, major flooding; 4,900 cubic feet per secondJan 1, 1961: 7.66 ft, minor flooding; 712 cubic feet per secondJan 7, 1962: 7.96 ft, minor flooding; 798 cubic feet per secondJun 3, 1963: 9.15 ft, moderate flooding; 1,440 cubic feet per secondFeb 16, 1964: 6.18 ft, action stage; 473 cubic feet per secondSep 21, 1966: 5.64 ft, action stage; 413 cubic feet per secondOct 19, 1966: 8.15 ft, moderate flooding; 870 cubic feet per secondJan 14, 1968: 6.78 ft, action stage; 696 cubic feet per secondAug 20, 1969: 13.34 ft, major flooding; 7,950 cubic feet per secondDec 26, 1969: 5.26 ft, action stage; 457 cubic feet per secondMay 30, 1971: 8.79 ft, moderate flooding; 1,280 cubic feet per secondJun 22, 1972: 9.75 ft, moderate flooding; 1,890 cubic feet per secondFeb 2, 1973: 7.35 ft, minor flooding; 828 cubic feet per secondMar 31, 1974: 5.98 ft, action stage; 559 cubic feet per secondMar 19, 1975: 7.02 ft, minor flooding; 804 cubic feet per secondJan 28, 1976: 6.32 ft, action stage; 676 cubic feet per secondJan 18, 1978: 7.62 ft, minor flooding; 934 cubic feet per secondFeb 25, 1979: 10.97 ft, major flooding; 3,160 cubic feet per secondJun 5, 1982: 5.15 ft, action stage; 491 cubic feet per secondApr 16, 1983: 8.63 ft, moderate flooding; 1,230 cubic feet per secondMay 30, 1984: 9.66 ft, moderate flooding; 1,820 cubic feet per secondSep 27, 1985: 10.93 ft, major flooding; 3,110 cubic feet per secondNov 30, 1985: 5.85 ft, action stage; 597 cubic feet per secondDec 25, 1986: 7.36 ft, minor flooding; 877 cubic feet per secondFeb 12, 1988: 5.86 ft, action stage; 598 cubic feet per secondJul 16, 1989: 7.76 ft, minor flooding; 968 cubic feet per secondMay 29, 1990: 10.28 ft, major flooding; 2,360 cubic feet per secondJan 12, 1991: 6.15 ft, action stage; 664 cubic feet per secondSep 6, 1992: 9.95 ft, moderate flooding; 2,050 cubic feet per secondMar 13, 1993: 8.25 ft, moderate flooding; 1,100 cubic feet per secondMar 3, 1994: 11.21 ft, major flooding; 3,470 cubic feet per secondJul 13, 1996: 8.61 ft, moderate flooding; 1,230 cubic feet per secondOct 19, 1996: 6.96 ft, action stage; 803 cubic feet per secondFeb 5, 1998: 11.27 ft, major flooding; 3,560 cubic feet per secondSep 16, 1999: 12.82 ft, major flooding; 6,560 cubic feet per secondJul 26, 2000: 8.64 ft, moderate flooding; 1,240 cubic feet per secondAug 13, 2001: 5.78 ft, action stage; 607 cubic feet per secondMay 26, 2003: 6.96 ft, action stage; 803 cubic feet per secondJul 27, 2004: 9.37 ft, moderate flooding; 1,610 cubic feet per secondApr 2, 2005: 6.31 ft, action stage; 689 cubic feet per secondMar 17, 2007: 7.98 ft, minor flooding; 1,020 cubic feet per secondJun 5, 2008: 9.51 ft, moderate flooding; 1,710 cubic feet per secondSep 30, 2010: 10.78 ft, major flooding; 2,920 cubic feet per secondAug 28, 2011: 12.98 ft, major flooding; 6,960 cubic feet per secondSep 2, 2012: 5.65 ft, action stage; 587 cubic feet per secondApr 20, 2015: 6.84 ft, action stage; 781 cubic feet per secondJun 28, 2015: 7.05 ft, minor flooding; 820 cubic feet per secondFeb 25, 2016: 6.97 ft, action stage; 805 cubic feet per secondJul 6, 2017: 6.77 ft, action stage; 769 cubic feet per secondMay 20, 2018: 7.90 ft, minor flooding; 999 cubic feet per secondJul 22, 2018: 6.19 ft, action stage; 670 cubic feet per secondNov 25, 2018: 6.00 ft, action stage; 640 cubic feet per secondJul 8, 2019: 7.45 ft, minor flooding; 905 cubic feet per secondAug 4, 2020: 11.57 ft, major flooding; 3,900 cubic feet per secondMar 24, 2021: 6.76 ft, action stage; 767 cubic feet per secondJun 10, 2021: 6.75 ft, action stage; 765 cubic feet per secondJul 9, 2021: 6.01 ft, action stage; 641 cubic feet per secondMay 24, 2022: 6.06 ft, action stage; 650 cubic feet per secondJul 26, 2022: 7.03 ft, minor flooding; 816 cubic feet per secondDec 16, 2022: 6.04 ft, action stage; 646 cubic feet per secondMay 1, 2023: 7.38 ft, minor flooding; 890 cubic feet per secondDec 18, 2023: 9.16 ft, moderate flooding; 1,476 cubic feet per secondJan 10, 2024: 7.72 ft, minor flooding; 961 cubic feet per second Highest, 13.34 ft, Aug 20, 1969 19501960197019801990200020102020

Crests at or above flood stage, by decade

Crests at or above flood stage per decade, St. Marys River at Great Mills 1940s: 3 1950s: 6 1960s: 6 1970s: 6 1980s: 5 1990s: 7 7 2000s: 4 2010s: 5 2020s: 5 1940s1950s1960s1970s1980s1990s2000s2010s2020s
  1. 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.
  2. 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

The 50 highest of 74 listed crests.

Highest listed crests, St. Marys River at Great Mills
1Aug 20, 196913.34+6.34Major7,950
2Aug 28, 201112.98+5.98Major6,960
3Sep 16, 199912.82+5.82Major6,560
4Jul 30, 196012.08+5.08Major4,900
5Aug 13, 195511.77+4.77Major4,350
6Aug 4, 202011.57+4.57Major3,900
7Feb 5, 199811.27+4.27Major3,560
8Mar 3, 199411.21+4.21Major3,470
9Feb 25, 197910.97+3.97Major3,160
10Sep 27, 198510.93+3.93Major3,110
11Aug 25, 195810.87+3.87Major3,030
12Sep 30, 201010.78+3.78Major2,920
13Nov 2, 195610.66+3.66Major2,780
14May 29, 199010.28+3.28Major2,360
15Sep 6, 19929.95+2.95Moderate2,050
16Jul 16, 19499.91+2.91Moderate2,020
17Jun 22, 19729.75+2.75Moderate1,890
18May 30, 19849.66+2.66Moderate1,820
19Jun 5, 20089.51+2.51Moderate1,710
20Jul 27, 20049.37+2.37Moderate1,610
21Aug 4, 19489.32+2.32Moderate1,560
22Dec 18, 20239.16+2.16Moderate1,476
23Jun 3, 19639.15+2.15Moderate1,440
24May 30, 19718.79+1.79Moderate1,280
25Jul 26, 20008.64+1.64Moderate1,240
26Apr 16, 19838.63+1.63Moderate1,230
27Jul 13, 19968.61+1.61Moderate1,230
28Mar 13, 19938.25+1.25Moderate1,100
29Oct 19, 19668.15+1.15Moderate870
30Mar 17, 20077.98+0.98Minor1,020
31Jan 7, 19627.96+0.96Minor798
32May 20, 20187.90+0.90Minor999
33Jul 16, 19897.76+0.76Minor968
34Jan 10, 20247.72+0.72Minor961
35Aug 14, 19537.68+0.68Minor656
36Oct 31, 19497.67+0.67Minor659
37Jan 1, 19617.66+0.66Minor712
38Jan 18, 19787.62+0.62Minor934
39Jul 8, 20197.45+0.45Minor905
40Jan 29, 19527.44+0.44Minor620
41May 1, 20237.38+0.38Minor890
42Dec 25, 19867.36+0.36Minor877
43Feb 2, 19737.35+0.35Minor828
44Jul 15, 19597.09+0.09Minor580
45Jun 28, 20157.05+0.05Minor820
46Jul 26, 20227.03+0.03Minor816
47Mar 19, 19757.02+0.02Minor804
48Feb 25, 20166.97−0.03Action805
49Oct 19, 19966.96−0.04Action803
50May 26, 20036.96−0.04Action803

Other gauges in St. Mary's County

Flood gauges in St. Mary's County
Clements7.07.63 ft, Aug 28, 20110
Straits Point (IN MLLW)3.54.90 ft, Oct 29, 20210

St. Mary's County: every hazard · River floods across the country · Maryland

NOAA National Water Prediction Service, gauge GMRM2, 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.