Every time I step into our unfinished basement, I am reminded of the 6-inch deep sloshing waters that flooded this place six years ago when we just moved in. It was after this huge rainfall on an evening in July, and my dad and I shoveled tirelessly for days to remove the sitting water. Today, the basement still contains the marks of the floodwater and the legacy it leaves behind.
For reference, I live in Ellicott City, Maryland. This small town just southwest of Baltimore is developed in a unique way, as the downtown district is placed within a deep valley surrounded by higher ground, almost like a hole. Fortunately, my house is on the elevated part of the city.
Because of the topography of Ellicott City and its proximity to the Patapsco River, our town is notorious for catastrophic flash floods after thunderstorms. It is probably one of the most flooded towns in the nation. In fact, it has flooded over 17 times since its founding in 1772.
In recent years, Ellicott City has been the unfortunate victim of two back-to-back once-a-millennium flooding events. On July 30, 2016, and May 27, 2018, severe thunderstorms downpoured 6.60 inches and 6.56 inches of rain within a 3-hour period in the late afternoon (Observed data recorded almost 9 inches). 2 fatalities were recorded in the first flood, and only 1 was recorded in the second. However, the structural damage done to 250 buildings and roads downtown was irreversible, and many are still being repaired today. What’s even worse was how the second flood came only 2 years after the 1st – homes and businesses were still recovering by the time the second occurred. My mom, whose office (as an architect) was in the heart of downtown, still recalls the fear that people felt that day. Many residents remember too. Fortunately, she and most others left just in time before the worst of the storm.
But what exactly is it about Ellicott City’s topography that attracts these floods and so much rain as well? The town sits at the confluence of three rivers, the Hudson, Tiber, and New Cut Branches, which all feed into the larger Patapsco River to the east. In the 2016 and 2018 floods, the three branches overflowed into the streets because they couldn’t drain fast enough into the Patapsco River, which was already rising rapidly. To make things worse, most surfaces in Ellicott City, such as concrete, blacktop, and pavement, could not absorb water. With nowhere to go, the massive stream rushed down Main Street.
Peak water discharges during each flood were astounding: 8,170 cubic feet per second during the 2016 event and 11,860 cubic feet per second during 2018. The water height soared to 5-10 feet, inundating entire first floors and basements and washing away vehicles.
However, what’s equally astonishing is the amount of rainwater that fell in a few hours. The 6-9 inches of rain that drenched Ellicott City was extremely localized in both events – perhaps this is a case of atmospheric memory or bad luck. In the 2018 event, a stalled west-to-east front (descended from New England) settled over central Maryland as a potent low-pressure system developed. With winds blowing from west to east, a train of thunderstorms developed and moved along the stalled front, battering a narrow region over and over again. Coincidentally, Ellicott City was right at the heart of this train of storms.
This exact phenomenon is called “cell” or “echo training” and happens often across the US. However, for it to target Ellicott City and a nearby city in Maryland, Frederick, only two weeks earlier is unusual.
These back-to-back flooding events are estimated to be 1-out-of-1000-year occurrences. Is that out of pure misfortune? Yes and no. Naturally, many ask whether climate change is causing more flash floods. While climate change is not responsible for the localized nature of these events, as it is associated with gradual trends over broader regions and periods of time, it has likely altered the overarching atmospheric setup to be more favorable for heavy rains. However, many meteorologists are reserved about correlating climate change to severe weather. We’re still determining if this is entirely true.
Today, Ellicott City has begun taking measures to improve stormwater removal and reduce the damage of potential floods in the future. Hopefully, our town serves as an example to cities across the US that you’ll never know when tragedy strikes again.
Works Cited
Cioffi, Chris. “Why Does Ellicott City Keep Flooding? And What Other Local Areas Are at Risk?” WTOP News, 4 June 2018, wtop.com/howard-county/2018/06/ellicott-city-keep-flooding-local-areas-risk/.
Doheny, Edward J. “Storms and Floods of July 30, 2016, and May 27, 2018, in Ellicott City, Howard County, Maryland.” United States Geological Survey, pubs.usgs.gov/publication/fs20213025.
“Flash Flooding Hits Ellicott City, Maryland.” YouTube, uploaded by CBS News, 27 May 2018, http://www.youtube.com/watch?v=Mgs4uC3mcQ8.
Halverson, Jeffrey. “The Second 1,000-year Rainstorm in Two Years Engulfed Ellicott City. Here’s How it Happened.” The Washington Post, 28 May 2018, http://www.washingtonpost.com/news/capital-weather-gang/wp/2018/05/28/the-second-1000-year-rainstorm-in-two-years-engulfed-ellicott-city-heres-how-it-happened/
