Many area rivers and large tributaries are approaching or have passed flood stage following today’s record-breaking rain, and are primed to crest in the next day or so.
While most area creeks and streams are now receding, the overflow from those smaller tributaries is just beginning to collect in area river basins.
Major flooding is forecast for the Potomac in Georgetown Saturday night, as the river exceeds flood stage by almost five feet, reaching 10.7 feet.
The National Weather Service provides the following flooding impacts associated with the different levels:
11 FT: THE RIVER REACHES A HEIGHT IN WHICH USUAL HIGH AND LOW TIDES ARE NO LONGER OBSERVED. FROM THIS POINT THE RIVER WILL RISE UNTIL CREST AND THEN FALL.
10.5 FT: FLOODWATERS REACH THE FOOT OF 17TH STREET AT INDEPENDENCE AVENUE.
10 FT: FLOODWATERS APPROACH K STREET IN GEORGETOWN NEAR WASHINGTON HARBOUR.
8 FT: BACKWATER FLOODING OF ROCK CREEK IN GEORGETOWN BEGINS AT THIS LEVEL.
7.5 FT: WASHINGTON HARBOUR WILL BEGIN TO FLOOD IF FLOODGATES ARE NOT IN PLACE.
Prior to cresting Saturday night, moderate flooding is possible during the day Saturday, especially around high tide.
Downstream in Alexandria, only minor flooding is predicted – with levels 1 to 1.5 feet above flood stage.
For reference, here are the next two high tides in Georgetown and Alexandria:
WASHINGTON CHANNEL [GEORGETOWN]…10:22 PM TONIGHT AND 10:26 AM SATURDAY…
ALEXANDRIA…10:40 PM AND 10:44 AM SATURDAY..
In the section of the Potomac meandering through Loudoun, Fairfax, and Montgomery County, the river is forecast to crest Saturday evening about 3.5 feet above flood stage at Little Falls – which is 10 feet. Warns the National Weather Service (NWS):
AT 14.0 FEET…SIGNIFICANT PORTIONS OF THE C & O CANAL TOWPATH ARE FLOODED. THE BLOCKHOUSE POINT PARK IS FLOODED. THE RAPIDLY RISING WATER WILL CAUSE PROBLEMS FOR INTERESTS NEAR THE RIVER. IF CAMPING OR RECREATING ALONG THE TOWPATH…MOVE TO HIGHERGROUND NOW!
Up river, at Point of Rocks, the Potomac is expected to crest mid-afternoon Saturday at 24.9 feet which is about 9 feet above flood stage.
Working further upstream, the Potomac’s forecast to reach peak levels late Saturday morning in Harper’s Ferry about five feet above flood stage (23.4 feet). Says the NWS:
AT 23.5 FEET…WATER APPROACHES JOHN BROWNS FORT IN HISTORIC HARPERS FERRY. WATER SURROUNDS THE BOOKSHOP AND A PLACE IN TIME MUSEUM. WATER SURROUNDS THE BLACKSMITHS SHOP. POTOMAC STREET BEGINS TO FLOOD AT THE INTERSECTION WITH SHENANDOAH STREET.
To the south, the Shenandoah River around Front Royal is predicted to crest tonight about five feet above flood stage.
Heading up towards Frederick, the Monocacy River is expected to crest tonight at 17.4 feet, just over 2 feet above flood stage.
In addition to all of the above locations, river flood warnings are in effect for sections of the Rappahanock and Rapidan rivers as well. Refer to the NWS for the full set of flood warnings.