Ellicott City Flooding

Ellicott City experienced historic flooding on Saturday, July 30 as 6.5 inches of rain was dumped on the area. The deluge sent a wave of floodwaters into the historic downtown area, where it caused massive damage to businesses and homes, swept cars downhill and killed at least two people. Click here to see an interactive timeline of the flooding.



Ellicott City is located in Howard County and includes a historic downtown near the Patapsco River. Main Street, where the worst of the flooding occurred, is located in a valley surrounded by streams and tributaries running into the Patapsco River.

Source: Google


Reported rain totals for the storm from around the area

Ellicott City

Source: National Weather Service


6.5 inches of total rainfall was reported in Ellicott City during the storm. The rain fell very heavily at times, including more than 4.5 inches of rain falling in an hour between 7:30 and 8:30 pm. Here are the heaviest rainfall totals within given increments of time.

Duration Amount Timeframe
1 minute .20 in 7:51-7:52 p.m.
5 minutes 0.80 in 7:50pm-7:55pm
10 minutes 1.44 in 7:50pm-8:00pm
15 minutes 2.04 in 7:46pm-8:01pm
20 minutes 2.48 in 7:44pm-8:04pm
30 minutes 3.16 in 7:36pm-8:06pm
60 minutes 4.56 in 7:30pm-8:30pm
90 minutes 5.52 in 7:00pm-8:30pm
2 hours 5.92 in 6:45pm-8:45pm

Source: National Weather Service

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 July 30 reached over 25 feet high (compared to normal water levels of 10-15 feet), according to a nearby gage maintained by the USGS.

Source: USGS

Water discharge from the Patapsco River

The same water gage measured over 30,000 cubic feet of water-per-second being discharged from the Patapsco River on July 30 during the storm, as compared to around 50 cubic feet of water-per-second being discharged on July 25-27.

Source: USGS

Historic levels on the Patapsco River

According to the same gage on the Patapsco, the river in that area reached new heights. The last major flood to hit Ellicott City was in 2011, and this one was about 3 feet higher, said Jason Elliott, a hydrologist with the National Weather Service's Baltimore/Washington forecast office. The Patapsco river levels peaked in 2011 at 25.17 feet and Saturday's flood reached 27.14 feet.

7/30/201627.14 ft. 9//7/201125.17 ft. 4/30/201423.83 ft. 1/31/201322.62 ft. 11/23/201118.5 ft.

By the numbers

4.5 inches of rain fell within one hour, from 7:30 p.m. to 8:30 p.m.

6.5 total inches of rain fell on Ellicott City during the storm

The Patapsco River rose 14 feet from about 7:20 p.m. to 9 p.m.

Two people died in the storm
Jessica Watsula of Lebanon, Pa
Joseph Anthony Blevins of Windsor Mill

4 to 5 buildings on Main Street were totally destroyed

20 to 30 buildings sustained significant damage

About 170 cars were being towed from the area to Centennial High School

This was the worst storm in Howard County since Tropical Storm Agnes in 1972

Source: Howard County / National Weather Service