As our “winter” gives way to spring, however prematurely, I hope you are enjoying the opportunities to enjoy our island’s environmental treasures, our friendly neighborhoods and our various venues for interacting with neighbors and visitors.
New markers of island history
Thanks to the efforts of the Battery Gadsden Cultural Center, Council member Justin Novak and town staff, we now have three new wayside markers denoting what was going on at certain island locations way back in history. Each of them marks important sites when Fort Moultrie was an active, significant military defense installation.
You can find the new markers at the field on Middle Street between Stations 17 and 16; at Middle Street and Station 18; and in Stith Park. What do they mark? That’s your job to learn. Get out there and read them.
Would a Charleston peninsula wall affect us?
A while back, a neighbor posed a very interesting question about the proposed flood wall around the Charleston peninsula: If it were built to defend the peninsula from a storm surge, would the deflected water affect us on Sullivan’s Island?
I took the question to the most expert person I could think of, Lt. Col. Andrew C. Johannes, PMP, PE, PhD, who is commander and district engineer of the Charleston District, U.S. Army Corps of Engineers. Here is what he said:
“Potential water-related impacts to Sullivan’s Island due to a storm surge wall on Charleston peninsula would be negligible. A simple analogy would be similar to placing a large rock into a large pool. You will not see any difference in water surface elevation based on the weight and size of the rock due to the size of the pool. This is a similar case for the storm surge wall and the large bodies of water that surround the Peninsula like Charleston Harbor and Cooper and Ashley Rivers.”
He goes on to quote from the Corps’ major report on this. I have shown with elipses “...” where I omitted very detailed items.:
“Since release of the draft FR/EA in April of 2020, the potential for the proposed storm surge wall to deflect water and impact surrounding communities was analyzed using the Advanced Circulation Model (ADCIRC, a state-of-the-art modeling software developed and frequently used by research institutions, industry and other government entities to simulate and closely analyze complex storm systems). The analysis examined the potential for induced flooding in James Island, West Ashley, North Charleston, Daniel Island and Mount Pleasant. …
“The study of impacts to adjacent communities modeled 11 severe, synthetic storms, both with and without the proposed storm surge wall. ‘Severe’ storms for purposes of the modeling were those with a storm surge equal to or in excess of the perimeter storm surge wall height. ‘Synthetic’ storms, as opposed to historic storm events, are used to facilitate modeling of a broad range of storm characteristics. Generated by the Federal Emergency Management Agency, the synthetic storms were selected based on their probable alignment to Charleston’s climate and hurricane history and included events producing storm surges of nine to more than 17 feet NAVD88. The storms varied in characteristics such as wind speed, storm path, size and overall intensity. The analysis also integrated a projected intermediate sea level rise of 1.65 feet, charting and comparing water surface elevations with and without a federal project across significant storm surge flooding events both today and into 2082, the study’s 50-year period of analysis.
“The modeling results indicated that the storm surge wall would induce a marginal difference in water surface elevations in the surrounding communities. … Water surface elevations ranged from an increase or decrease of less than 1 inch depending on location. This marginal difference in water surface elevation is in addition to what would have statistically occurred in these areas. … Structural damages as a result of the marginal differences in water surface elevations in surrounding communities would be highly unlikely, therefore this analysis suggests that the construction of a wall on the Charleston peninsula would have a negligible adverse effect of increased flooding damages to surrounding communities during a storm surge event.”
Thank you, Lt. Col. Johannes, for this very helpful and expert information. And here’s hoping we never experience the worst of those synthetic storms in real life.
See you around the island!
Pat O’Neil, Mayor
843-670-9266
Twitter: @oneilpm1
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