PROJECT ALERT NOTICE (MD) Field Response to Heavy Rain and Flooding in Central Maryland

Date: Tue, 29 May 2018 10:09:24 EDT

Summary: Heavy rain in central Maryland on Sunday, May 27, 2018 caused severe localized flooding and minor damage to some streamflow gages.

On Sunday afternoon, May 27, 2018, at least 8 to 10 inches of precipitation fell over Ellicott City, Catonsville, and surrounding vicinities in central Maryland. The precipitation caused significant flooding and property damage in the affected area. Annual-exceedance probability for the precipitation is likely in range of 0.1 percent. Initial estimates of annual-exceedance probabilities for streamflows resulting from the precipitation range from 10 percent to 0.5 percent. One person is missing in Ellicott City, and extensive, severe property and public infrastructure damage has been sustained there. Property damage and inundation was also experienced in the vicinity of Catonsville. The runoff from the precipitation has occurred primarily in the Patapsco River and Patuxent River watersheds. One gage on the mainstem of the Patapsco River (7 years of data) experienced a peak of record. Two gages in the Dead Run sub-watershed of the Patapsco River basin were damaged and made inoperable.
USGS personnel are deployed to identify high-water marks today at a number of USGS gages in the area. The deployment includes 4 crews, totaling 10 staff. One of the four crews will also be collecting sediment samples on the mainstem Patapsco River.
USGS is awaiting permission to access the Ellicott City area to identify high-water marks along the three major tributaries draining through the historic district that sustained heavy flood damage.