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Charleston's Chief Resilience Officer Mark Wilbert checks on a pump at Norman and Allway streets in Gadsden Green Homes on Dec. 9, 2018. Less-than-expected rainfall during Sunday morning's above-average high tide helped keep flood levels below officials' projections. Wade Spees/Staff

Knowing that Sunday's forecast called for heavy rains to arrive around the same time as a very high tide, the city of Charleston scrambled to position portable pumps to help its most flood-prone streets.

Shannon Scaff, the city's emergency management director, said he was pleased with the results.

"Overall, we didn’t see anything that was of real significance," he said. "I feel like it worked out."

The city stationed portable pumps — each capable of moving about 1,000 gallons a minute — at the following locations:

  • Allway and Norman streets, near the Septima P. Clark Parkway
  • Gadsden and Bennett streets
  • Broad Street and Ashley Avenue
  • Broad and Colonial streets
  • King and Huger streets

Even though the rainfall during Sunday morning's high tide was less than expected, all the pumps were activated and helped move water from low-lying spots.

Aside from tropical storms and hurricanes, Charleston's worst flooding often occurs when a heavy rain arrives around high tide, when downtown's drainage lines have less capacity.

Scaff, who began work with the city five months ago, had not seen those coincide, "so the level of apprehension in my office was higher."

While Scaff wouldn't go as far as calling this network of temporary pumps a new normal, he said the city would consider redeploying them the next time a heavy rain is forecast to coincide with a very high tide. 

The city recently installed more than a dozen new backflow preventers to reduce its so-called "sunny day flooding," which happens when exceptionally high tides push saltwater back up through drainage lines and onto city streets. But those devices don't help areas during a rainfall.

Bobbie Rose, who lives in Harleston Village near Gadsden and Bennett streets, said the city's new check valves have worked well and the new pumps added Sunday appeared to work, too.

"Over the weekend, I was nervous," she said. "At the worst point, the corner was under water by about 4 inches, but that was it. ... That corner can easily be a foot under water in these kind of circumstances."

The city has used temporary pumps to clear water off streets, such as it did in 2016 after Hurricane Matthew, whose floodwaters didn't drain from around Broad Street and Rutledge Avenue because of a blocked pipe.

In its preparation for Sunday's rains and 8.1-foot high tide, the city also issued public warnings, pre-positioned its fleet of Jet Vactor trucks to respond quickly to any clogged drains and opened its Queen Street parking garage for those who wanted to move their vehicles away from flood spots.

"We as a group, from the mayor on down, are very forward leaning on this,” Scaff said.

Reach Robert Behre at 843-937-5771. Follow him on Twitter @RobertFBehre.

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