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Charleston remains exposed, vulnerable to flooding and earthquakes

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Water laps against homes on Vanderhorst Street after heavy rains on Sept. 25, 2020, in Charleston. File/Grace Beahm Alford/Staff

The same day Charleston warned residents to prepare for coastal flooding and rising waters, the harsh realities of the city's vulnerability to disasters was dropped on government leaders.

A long-anticipated 191-page assessment of the pressure points in the city's housing, job markets and medical district was released showing the area faces potentially tragic consequences if Mother Nature delivered her worst. 

"Charleston is one of the nation's most historic coastal communities and is among the first facing the impacts of a changing climate and sea-level rise," an executive summary of the report said.

"It is also one of only a few communities on the east coast located in an area of potential seismic activity," it continued.

The report took into account Charleston's commonplace issues with flooding and storm surge but also catastrophic occurrences such as earthquakes and hazardous material leaks. 

The report identified nine hazards, including four different types of flooding: floodplain inundation, storm surge, tidal flooding and sea-level rise, along with earthquakes, hazardous materials release, extreme heat and water shortage.

The peninsula proper would be the most impacted financially, as 65 percent of all the jobs citywide are located there.

The most vulnerable for home loss or damage — 30 percent — are in inner West Ashley.

Eighty-six percent of properties citywide could become inaccessible during a major flood event, the report said.

Here is how categories were broken down in the report:

Floodplain inundation

  • 71 percent of businesses, 70 percent of homes and 59 percent of critical facilities are vulnerable to floodplain inundation, or dry areas that are prone to flooding.
  • More than half of all flood-prone properties were built before floodplain development requirements were enacted.
  • Public housing properties are also proportionately more vulnerable to flooding based on the FEMA floodplains compared to other residential properties in the city. 

Storm surge

  • 84 percent of businesses, 87 percent of homes, and 72 percent of critical facilities are vulnerable to storm surge, or water that rises after a significant weather event.
  • The most vulnerable areas include the peninsula, inner West Ashley and northern James Island. 
  • "Lifelines and critical areas are potentially inaccessible during current tidal flooding events," the report said. "Several residential areas are potentially isolated during tidal events due to inaccessible minor or residential roads."

Earthquakes

  • 46 percent of businesses, 39 percent of homes, and 88 percent of critical facilities are vulnerable to earthquakes.
  • Most vulnerable areas: peninsula, inner and outer West Ashley and northern James Island.
  • About 36 percent of constructed buildings in the city were built before the first building code was established in 1968, including 530 historic properties built before the last earthquake in 1886. Since those buildings already experienced an earthquake they are more vulnerable now. 
  • About 44 percent of bridges in the city are highly vulnerable because they do not have seismic design considerations, the report read.

The assessment was compiled by North Carolina-based UNC Asheville’s National Environmental Modeling and Analysis Center+FernLeaf. They have been collecting data from publicly available sources from March 2019 to March 2020.

FernLeaf has done work in Tallahassee, Fla., North Carolina and for the National Wildlife Foundation. The assessment cost the city approximately $200,000. 

Earlier this year, the consultant gave City Council an update on their progress, and said a final report would be forthcoming. It wasn't publicized until Thursday, Chief Resilience Officer Mark Wilbert said, because of an extensive city review process and pending documentation approval from federal agencies.

The summary did find positives. It touts Charleston as one of the first cities in the state to create an office of resilience and emergency management — comprised of emergency managers, sustainability and resiliency officers — and that Charleston is among the first in the Southeast to have a flooding and sea-level rise strategy.

"We knew we needed to have a fuller, more detailed understanding of the challenges our city will be facing in the future — and that's exactly what this report has given us,” Mayor John Tecklenburg said in an email statement. “It will be an invaluable planning tool for years to come, as we tackle tough issues ranging from land use, to flooding defenses, to public safety and affordable housing and more."

Wilbert told city leaders Thursday that the vulnerability assessment report is being used as a resource while the city updates its comprehensive plan and also its response to the Army Corps of Engineers' suggested flood wall around the city.

Reach Mikaela Porter at 843-937-5906. Follow her on Twitter @mikaelareporter. 

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