Updated, Thursday 4:30 p.m.: The flooding threat is over for the Potomac River near Little Falls. National Weather Service estimates show the peak flood stage of 10.33 feet on Wednesday to have passed.
At 4:30 p.m. Thursday the river measured at 7.1 feet.
Updated, Tuesday 11 p.m.: Minor flooding is still expected of the Potomac River near Little Falls, though National Weather Service estimates have decreased the peak estimated flood stage to 11.4 feet on Thursday, down from Monday’s estimate of 15.3 feet.
At 11 p.m. Tuesday the river measured at 8.93 feet.
National Weather Service estimates continue to show flooding in areas south of Little Falls.
Updated, Tuesday 10 a.m.: Moderate flooding is still expected of the Potomac River near Little Falls, though National Weather Service estimates have decreased the peak estimated flood stage to 12.2 feet on Thursday, down from Monday’s estimate of 15. 3 feet.
At 9 a.m. Tuesday the river measured at 7.8 feet.
Original Story, Monday: The Potomac River is expected to flood by late Tuesday evening, contributing to what may be the worst deluge this region has seen in 40 years.
The National Weather Service (NWS) has issued a flood warning in effect Tuesday for the Potomac River near Little Falls and Point of Rocks. The flooding will affect Montgomery County, as well as Frederick and Loudoun counties in Virginia.
"Residents and businesses along the Potomac River from Hancock downstream to and including Washington DC should prepare for a flood not seen since the floods of 1996," an NWS release stated.
The river is expected to rise above the flood stage of 10 feet Tuesday evening, and continue to rise above 15 feet by Thursday morning, according to the NWS report.
At Little Falls, NWS considers a river stage above 14 feet as "major" flooding, according to its website.
In the C&O Canal National Historical Park, National Park Service officials have standard flood protection procedures underway, and were working to lower water levels in the canal and to secure the park's canal boat replica.
However, NPS teams were pulled from the park Monday due to high winds, said Park Service spokesman John Noel.
Crews will return when it’s safe to continue flood preparations, Noel said.
The park was closed to visitors Monday, and officials hadn't yet made a determination as to whether it would be open Tuesday.
“All floods have the potential to be damaging,” Noel said. “We have standard procedures we’re implementing so we can withstand any level of flood that may come.”
The flooding may pose a threat to historic lockhouses along the canal, some of which have been renovated by park advocacy group C&O Canal Trust as part of the group’s Canal Quarters program.
The renovated lockhouses at lower elevations – about half of the renovated structures, including Lockhouses 6, 22, 26, and 28 – are “under some amount of threat,” said Trust program manager Becky Curtis.
The Trust began work before the storm to protect the buildings and remove furniture from lower levels, but high winds Monday temporarily halted the preparation work.
Volunteers will return after winds die down to sandbag the houses, Curtis said.
“We’re hoping there’s a window between the storm surge now and the river crest,” Curtis said.
If the Potomac flood stage reaches 15 feet, most of the C&O Canal towpath below Edwards Ferry will be covered, access to Violette’s Lock in Potomac will be flooded and water will flow down the side walk near the Georgetown Visitors Center, according to the NWS report.
At 5 p.m. Monday, the river measured at 3.7 feet.
Smaller waterways around the county, including Seneca Creek have already flooded and are contributing to the larger flood of the river, according to the NWS.