On July 30, 2016, and May 27, 2018, the downtown area of Ellicott City, Maryland (fig. 1), was severely flooded by intense, short-duration rainfall that resulted in loss of life; significant damage to buildings, roads, infrastructure; and hundreds of vehicles washed away. Precipitation from the 2016 event totaled 6.60 inches in 3 hours (National Oceanic and Atmospheric Administration, 2016). Precipitation from the 2018 storm totaled 6.56 inches in 3 hours (National Oceanic and Atmospheric Administration, 2018).
In the aftermath of both storms, personnel from the U.S. Geological Survey (USGS) performed indirect discharge measurements to determine peak flow on the three streams that drain through the downtown area of Ellicott City and empty into the Patapsco River. High-water marks were flagged on selected reaches of three streams, Hudson Branch (station 01589017), Tiber Branch (station 01589019), and New Cut Branch (station 01589021) (fig. 2). Peak flows were computed using flow-through-culvert techniques with road overflow for Hudson Branch and slope-area techniques for Tiber Branch and New Cut Branch.
This fact sheet describes the basin characteristics, hydrologic characteristics, and flood history of the Ellicott City, Maryland, area. The storms and flood characteristics for July 30, 2016, and May 27, 2018, are described. Peak discharges computed from the indirect discharge measurements for Hudson Branch, Tiber Branch, and New Cut Branch are presented for the storms and floods of July 30, 2016, and May 27, 2018. To provide historical perspective on these floods in Ellicott City, results from the indirect discharge measurement computations were compared to peak flows from 75 USGS streamgages and 6 miscellaneous sites in Maryland and Delaware that resulted from intense storms in August and September 1971 (Carpenter, 1974). The findings indicate that although the Ellicott City storms and floods from July 30, 2016, and May 27, 2018, are considered very rare in terms of their probability of occurrence, other storms have occurred in the Maryland and Delaware regions in the past that have produced comparable runoff characteristics relative to drainage-area magnitude.
Doheny, E.J., and Nealen, C.W., 2021, Storms and floods of July 30, 2016, and May 27, 2018, in Ellicott City, Howard County, Maryland: U.S. Geological Survey Fact Sheet 2021–3025, 6 p., https://doi.org/10.3133/fs20213025.
ISSN: 2327-6932 (online)
ISSN: 2327-6916 (print)
Table of Contents
- Description of Study Area
- History of Flooding in Ellicott City, Maryland
- Description of Storm and Flood of July 30, 2016
- Description of Storm and Flood of May 27, 2018
- Indirect Measurements of Peak Discharge in Ellicott City Watersheds
- Historical Perspective: July 2016 and May 2018 Floods
- References Cited
|Publication Subtype||USGS Numbered Series|
|Title||Storms and floods of July 30, 2016, and May 27, 2018, in Ellicott City, Howard County, Maryland|
|Series title||Fact Sheet|
|Publisher||U.S. Geological Survey|
|Publisher location||Reston, VA|
|Contributing office(s)||Maryland-Delaware-District of Columbia Water Science Center|
|Online Only (Y/N)||N|
|Additional Online Files (Y/N)||N|
|Google Analytic Metrics||Metrics page|