Potomac River at Point of Rocks, Frederick County MD (PORM2)
Gage Location: Frederick County, Maryland	Site Location: Frederick County, Maryland
Latitude: 39.274	Longitude: -77.543	Elevation: 200.63 ft. MSL	Drainage Area: 9651 Sq. Mi.
Minor Stage: 16 ft.	Moderate Stage: 20 ft.	Major Stage: 25 ft.
First Flood: 1889-06-02	Last Flood: 2012-10-31 Crest: 18.19 ft.	Datum change: 1929-10-28	Number of Floods: 114

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MINOR FLOODS Date of Flood Crest(ft) 1898-08-12 18 1899-03-06 18.1 1903-03-01 16.6 1907-03-15 17.6 1911-09-01 16.1 1916-03-29 18.3 1917-03-13 18.1 1918-04-16 18.6 1920-03-06 16.4 1929-10-23 17.4 1933-04-21 19.3 1934-12-02 19.78 1936-02-28 18.13 1939-02-05 19.39 1948-04-15 16.04 1950-12-09 18.42 1951-06-15 17.52 1952-03-13 17.12 1952-11-23 19.68 1954-03-03 18.65 1960-04-01 17.35 1960-04-06 18.25 1961-02-21 17.9 1961-02-27 16.6 1962-03-23 19.45 1963-03-07 17.6 1964-03-06 16 1965-03-06 17.35 1970-04-03 16.64 1972-10-08 18.28 1973-04-29 16.58 1976-01-02 18.71 1978-03-28 18.43 1978-05-17 17.67 1979-01-25 17.29 1979-09-07 16.19 1982-06-15 16.66 1983-04-26 19.21 1984-04-06 19.49 1986-03-16 19.35 1988-05-20 17.01 1992-04-23 16.25 1993-03-25 18.12 1993-04-03 18.19 1993-11-29 19.25 1994-02-25 16.03 1994-03-11 17.78 1994-03-30 19 1996-01-28 16.53 1996-03-21 16.6 1997-11-09 17.37 1998-02-06 17.99 1998-02-19 18.23 2003-01-03 16.25 2003-02-24 16.5 2003-03-22 16.85 2003-12-12 19.58 2004-09-30 17.25 2005-03-30 19.37 2007-04-17 17 2008-05-13 16.99 2009-05-06 17.5 2011-03-12 19.92 2012-10-31 18.19

MODERATE FLOODS Date of Flood Crest(ft) 1901-04-22 22 1908-01-13 21.6 1910-06-18 23.5 1913-03-28 20 1915-06-04 20 1928-05-02 21.3 1929-04-18 24.94 1932-05-14 23.34 1937-10-30 24.93 1942-05-24 21.13 1942-12-31 20.47 1945-09-20 21.98 1949-06-20 21.2 1950-12-05 20.75 1952-04-29 20.67 1954-10-17 21.02 1960-05-10 20.28 1963-03-21 20.47 1967-03-08 22.53 1973-12-28 21.27 1975-09-26 24.35 1978-01-28 21.22 1978-03-16 22.01 1984-03-30 20.8 1987-04-18 23.49 1993-03-06 24.94 1993-04-18 20.17 1998-01-10 20.07 1998-03-22 20.24 2003-09-21 23.12 2010-01-26 21.42 2011-04-18 22.52 2011-05-19 22.15

MAJOR FLOODS Date of Flood Crest(ft) 1889-06-02 40.2 1896-10-01 27.2 1902-03-02 29 1924-05-13 32.2 1936-03-19 41.03 1937-04-27 33.86 1942-10-16 40.43 1955-08-20 29.08 1972-06-23 37.43 1975-03-21 26.15 1976-10-11 27.25 1979-02-27 25.94 1984-02-16 28.14 1985-11-07 36.28 1996-01-21 36.34 1996-09-08 36.26 2010-03-15 25.52

MISSING Date of Flood Crest(ft)

Categorical Floods by Month Month Minor After Datum Minor Total Moderate After Datum Moderate Total Major After Datum Major Total Missing After Datum Missing Total January 4 4 3 4 1 1 0 0 February 8 8 0 0 2 2 0 0 March 15 21 6 7 3 4 0 0 April 11 12 4 6 1 1 0 0 May 4 4 4 5 0 1 0 0 June 2 2 1 3 1 2 0 0 July 0 0 0 0 0 0 0 0 August 0 1 0 0 1 1 0 0 September 2 3 3 3 1 1 0 0 October 2 3 2 2 2 3 0 0 November 3 3 0 0 1 1 0 0 December 3 3 3 3 0 0 0 0

Categorical Floods by Season Season Minor Moderate Major Missing Fall 9 5 5 0 Winter 15 7 3 0 Spring 37 18 6 0 Summer 3 3 3 0

Codes and description

C1|Crest information looks unreliable and incomplete and not used in frequency calculations. Some of the floods are based on current flood stage and nearby gage information.
C2|Crest information looks reliable despite potential problems. This data was used in frequency calculations.
C3|Crest height estimated by the USGS.
C4|Crest height is from the National Weather Service.
C5|Crest height affected by backwater.
C6|Crest occurred at a previous flood stage that is lower than the current flood stage. The crests below the new flood stage are not used in flood frequency calculations.
C7|Crest from USGS yearly peak and/or date is different than the crest we provide. In many cases MARFC uses crest based on backwater or ice effects.
C8|Crest month or day of occurrence has been estimated by The Middle Atlantic River Forecast Center usually based on nearby gage information.
C9|Crest date (day) in the month is unknown.
F1|Flow is an estimate.
F2|Flow affected by regulation or diversion and in some cases to an unknown degree.
F3|Flow effected by snow-melt, ice jam or debris jam break up.
F4|Flow affected by dam failure.
F5|Flow - All or part of the record affected by urbanization, mining, agricultural changes, channelization or other factors.
G1|Gage height at a different site and/or datum.
G2|Gage is not an official USGS gage with crests provided by the NWS. Crest information looks unreliable and incomplete and not used in flood frequency calculations.
G3|Gage datum changed during this year.
none,No code; Good Data

Updated: 08:09 AM Feb 08, 2013