7/25/2023 0 Comments Old ellicott city floodFor this reason alone, the region is prone to flooding. On Saturday, July 30, 2016, torrential rains passed through Howard County, Maryland resulting in severe flash flooding through historic downtown Ellicott City. It sits near the Patapsco river and in a valley. ![]() Ellicott City, Maryland has flooded 15 or so times in the past couple of centuries. Neil Debbage, who was recently hired to join the Faculty at University of Texas-San Antonio, confirmed that urban development also affects streamflow. Forty years ago on June 23, flooding from Hurricane Agnes hit the Patapsco River Valley area, devastating the state park, wiping out old mill towns and severely flooding Ellicott City. New research published in Water Resources Research by Dr. It reduces infiltration and increases the amount of water runoff into streams. 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. May 27 marks the 5-year anniversary of the last deadly and devastating flood in Ellicott City, Maryland. The Baltimore region, like many others, is becoming more urbanized. This leads me to the next aspect of the water cycle lesson. Once again, many storefronts and buildings up and down the historic downtown were severely damaged, including homes and businesses that had only recently. ![]() ![]() 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. 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.
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