Potomac River at Point of Rocks, MD - 01638500

LOCATION.--On left bank at downstream side of bridge on U.S. Highway 15 at Point of Rocks, 0.3 mi downstream from Catoctin Creek (Virginia), 6 mi upstream from Monocacy River, and at mile 159.5. PERIOD OF RECORD.-- February 1895 to current year. GAGE.-- Water-stage recorder and crest-stage gage. Datum of gage is 199.91 ft above North American Vertical Datum of 1988. Prior to Oct. 28, 1929, nonrecording gage at same site. Prior to Sept. 2, 1902, at gage datum about 0.45 ft higher. REMARKS.--Low flow affected slightly from 1913 to July 1981 by Stony River Reservoir; since December 1950 by Savage River Reservoir (see station 01597500); and since July 1981 by Jennings Randolph Lake. Low flow affected extensively at times by run-of-the-river hydroelectric plants. EXTREMES OUTSIDE PERIOD OF RECORD.-- Flood of June 2, 1889, reached a stage of 40.2 ft, from floodmarks, discharge, about 460,000 ft³/s from rating curve extended above 300,000 ft³/s, on basis of adjustment of figure of peak flow at station near Washington for inflow and storage, and slope-area measurement of peak flow.