Ellicott City experienced its second historic flood in two years on Sunday, May 27, as over 7 inches of rain fell on the city. The flooding caused major power outages and damaged businesses and homes in the historic downtown area.
Ellicott City is located in Howard County and includes a historic downtown near the Patapsco River. Main Street, where much of the flooding occured, is located in a valley surrounded by streams and tributaries running into the Patapsco River.
Reported rain totals for the storm from around the area
Source: National Weather Service
Historic levels on the Patapsco River
A gauge on the Patapsco recorded water surface levels reaching close to those of the Ellicott City flood just two years earlier. The Patapsco river levels peaked in 2016 at 27.14 feet and Sunday's flood reached 27.03 feet.
WATER LEVELS IN THE PATAPSCO RIVER
Much of the damage was a result of flooding from the nearby Patapsco River, the flow of which is regulated by Liberty Reservoir (approximately 18 miles upstream). Water levels on the Patapsco River on May 27 reached over 27 feet high (compared to previous water levels around 11 feet), according to a nearby gage maintained by the USGS.
WATER DISCHARGE FROM THE PATAPSCO RIVER
The same water gauge measured over 25,000 cubic feet of water-per-second being discharged from the Patapsco River on May 27 during the storm, as compared to around 200-300 cubic feet of water-per-second being discharged on May 26.