PROJECT ALERT NOTICE (MD) USGS Response to May 27, 2018 Flooding in Central Maryland Continues

Date: Wed, 30 May 2018 06:49:51 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 lost his life 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 several USGS gages in the area. The deployment includes two crews, totaling eight staff. One of those crews will access the Ellicott City area today to identify high-water marks along the three major tributaries draining through the historic district that sustained heavy flood damage. A third crew, comprised of two staff, will be effecting repairs to a USGS sediment-monitoring site on the mainstem Patapsco River.