Perkiomen Creek at Graterford, Montgomery County PA (GRAP1)
Gage Location: Montgomery County, Pennsylvania	Site Location: Montgomery County, Pennsylvania
Latitude: 40.229	Longitude: -75.452	Elevation: 112.66 ft. MSL	Drainage Area: 279 Sq. Mi.
Minor Stage: 11 ft.	Moderate Stage: 13 ft.	Major Stage: 16 ft.
First Flood: 1915-01-07	Last Flood: 2013-01-31 Crest: 12.49 ft.	Datum change: 1927-09-14	Number of Floods: 81

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MINOR FLOODS Date of Flood Crest(ft) 1918-02-20 12.7 1929-02-26 11.22 1929-10-02 11.62 1934-09-30 12.34 1935-09-04 11.55 1936-01-03 11.4 1940-03-15 12.71 1943-06-18 11.62 1943-11-09 11.43 1945-01-01 11.94 1946-07-23 12.18 1948-12-30 11.85 1952-04-28 11.21 1952-07-10 11.15 1952-12-11 12.49 1953-01-24 11.31 1955-10-15 12.72 1958-02-28 11.23 1965-02-08 11.11 1967-03-07 11.86 1968-05-31 11.75 1969-07-29 11.17 1970-04-02 12.2 1972-11-14 11.8 1975-07-14 12.39 1977-03-23 12.19 1982-01-04 11.1 1983-04-10 11.7 1989-09-20 11.08 2000-03-22 11.89 2002-05-14 12.52 2003-09-15 12.43 2003-10-27 12.08 2004-07-28 12.49 2004-09-29 12.53 2005-03-28 11.18 2007-04-15 12.43 2008-02-13 12.08 2008-12-12 12.91 2011-11-23 12.61 2013-01-31 12.49

MODERATE FLOODS Date of Flood Crest(ft) 1915-01-07 14.33 1915-01-13 13.98 1915-02-01 14.83 1928-07-14 13.36 1938-09-21 13.5 1940-05-20 13.28 1942-08-09 15.5 1950-11-25 14.6 1952-11-22 13.36 1955-08-13 14.26 1955-08-19 14.08 1960-09-12 14.55 1971-09-14 14.67 1973-12-21 13.04 1978-01-26 13.03 1979-01-25 14.79 1984-07-07 15.06 1985-09-27 13.19 1990-05-30 13 1993-12-05 14.65 1995-03-09 13.29 1996-10-19 15.67 2000-12-17 13.71 2003-06-21 13.78 2004-09-18 14.8 2005-04-03 14.17 2005-10-08 14.9 2006-06-28 13.66 2010-10-01 14.18 2011-09-07 13.93

MAJOR FLOODS Date of Flood Crest(ft) 1933-08-23 16.65 1935-07-09 18.26 1946-06-02 16.23 1972-06-22 17.08 1996-01-19 16.45 1999-09-16 16.59 2011-08-28 18.2

MISSING Date of Flood Crest(ft) 1915-08-04 -9999 1918-02-15 -9999 1919-07-21 -9999

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 5 5 2 4 1 1 0 0 February 4 5 0 1 0 0 0 1 March 5 5 1 1 0 0 0 0 April 4 4 1 1 0 0 0 0 May 2 2 2 2 0 0 0 0 June 1 1 2 2 2 2 0 0 July 5 5 2 2 1 1 0 1 August 0 0 3 3 2 2 0 1 September 5 5 6 6 1 1 0 0 October 3 3 3 3 0 0 0 0 November 3 3 2 2 0 0 0 0 December 3 3 3 3 0 0 0 0

Categorical Floods by Season Season Minor Moderate Major Missing Fall 11 11 1 0 Winter 13 8 1 1 Spring 11 4 0 0 Summer 6 7 5 2

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