However, urbanization modifies the water cycle. In the natural landscape, water infiltrates into the soil. Cityscapes tend to have lots of parking lots, paved roads, and surfaces that water does not seep into.
The Baltimore region, like many others, is becoming more urbanized. This leads me to the next aspect of the water cycle lesson. Over the span of a few hours 6 to 12 inches of rainfall fell in the Ellicott City, Maryland region.Ĭlimatological Precipitable Water range for 00Z on May 28th at Washington-Baltomore area NWS office. Jeff Halverson writes in Capital Weather Gang that "precipitable (water) value was nearly record-breaking for this region, for May 27." With values near 2 inches, it is clear from the climatological PW analysis below that this was an anomalous event. So what is Precipitable Water? It is defined by the American Meteorological Society Glossary of Meteorology as, "the total atmospheric water vapor contained in a vertical column of unit cross-sectional area extending between any two specified levels, commonly expressed in terms of the height to which that water substance would stand if completely condensed and collected in a vessel of the same unit cross section." Preliminary analyses suggest that the 2018 Ellicott City flooding was also associated with extremely high moisture rates. She also found that in all 40 flood cases examined in the study, the PW values exceeded 150% of climatological mean values. That may not sound like a lot, but any additional rainfall will exacerbate the flooding from the rain that has already fallen, and this will delay river levels from receding below flood stage quickly, CNN’s Allison Chinchar said.A key finding was that urban flood events are often associated with extremely high Precipitable Water (PW) and often exceed the 99th percentile of the dataset. The NWS provided observed rainfall accumulations for the past 24 hours in the greater Baltimore area showing widespread observed amounts of 3 to 6 inches with isolated measurements exceeding 9 inches.Īdditional rainfall amounts of 1 inch could come, the NWS said. The National Weather Service issued a flash flood warning for northeastern Anne Arundel County and southeastern Howard County through earl Monday. The river rose 17.8 feet in two hours on Sunday afternoon to 24.13 feet, a new record from the previous high of 23.6 feet. Located in the valley of the Patapsco River, a major waterway flowing to Chesapeake Bay, Ellicott City is known for its flood-prone location as much as its historic downtown. “It’s heartbreaking.”Įllicott City is an unincorporated community about 12 miles west of Baltimore. The city rallied around the slogan “Elliott City Strong.” Many businesses had just finished rebuilding, Kittleman said.
Gas lines were shut down and a historic building fell, he told reporters. Kittleman said the flooding was worse than that endured in July 2016. The disaster left two dead and damaged dozens of buildings. The devastation was especially hard to comprehend coming barely two years after the last flood that ravaged the city, he said. The circumstances were not immediately known. One person was missing following the Ellicott City flooding, Howard County Executive Allan Kittleman said Monday morning. In some areas, water levels reached above the first floor of buildings, Howard County Fire and EMS Ellicott City Flooded Again /2PZ62QlNR5- zack May 27, 2018 Thirty rescues were carried out into Monday morning, officials said.īrown water rushed through Ellicott City’s historic Main Street, toppling buildings and upending cars, as the nearby Patapsco River swelled to a record-breaking level. Larry Hogan declared a state of emergency Sunday in Howard County as a massive storm drenched the Baltimore region, triggering flash floods in Ellicott City and leaving one person missing.
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