Posted on April 22, 2019
“You don’t even get weeks’ worth of protection; it goes away before the next significant storm hits.”
WILMINGTON — After coastal engineer Chris Gibson called Surf City’s recent $300,000 beach push operation an “emotional benefit,” we caught up with coastal erosion specialist Spencer Rogers to get his take.
Rogers works with the North Carolina Sea Grant and is based out of UNCW’s Center for Marine Science. After Hurricane Florence caused significant erosion to Topsail Island’s beach and dune systems, Rogers inspected the beaches all along the island; he also held a beach nourishment workshop in Surf City last February.
Gibson described a beach push as an “emotional benefit” — it essentially gives people a feeling of comfort and safety.
That’s a good description.
So what is a beach push exactly?
It goes by a bunch of different names: beach bulldozing or beach scraping, depending on where you are. It’s basically an effort, usually involving a piece of heavy equipment, to re-arrange the shape of the beach.
And it makes a steeper slope, right?
It makes it a different slope — part steeper, part flatter. The shape of the beach is not an accident. It’s a shape that is moving towards some equilibrium based on three primary factors: the size of the waves, the water level, and the grain size of the sand.
Florence generated a lot of temporary erosion. This equilibrium shape of the beach is driven by these larger events like Florence and Floyd and Fran, events that are so far out of the normal water level and wave heights that it erodes the entire berm — the sandy beach where you put your beach blanket — and it starts taking sand out of the dunes. And if the dunes aren’t big enough, it’ll overwash and send water and waves into the base side of the shoreline.
The erosion in a hurricane takes place in a matter of hours — in the case of Florence, three days. The recovery begins immediately but it is subtle and it can take months to years for the sand to get back to the berm. And because the dunes are features of the wind, it can take years to decades to get back into the dunes.
Surf City had so much FEMA money that it could spend on doing a sand-haul operation, and they used it for areas deemed “critically imminent.” The remaining areas were marked for this beach push operation. What would give a municipality a reason for doing a beach push?
First is the mindset of the people there. Last month, I did a dune repair workshop in Surf City. Out of 110 people present, probably 70 of them were property owners on the island. But my next question was: How many had been there for more than 25 years? And the number dropped to about ten — out of 110.
Florence was the worst storm that those 60 people had ever seen, but if you go back to Hurricane Fran and Floyd — Fran in ’96 and Floyd in ’99 — the conditions on the island were actually much worse.
In Hurricane Fran, Topsail Island lost 180 houses on the oceanfront. And as best I can tell, in Florence, it lost one building to erosion and wave damage. There were many others that had roof damage and water penetration and things like that, which caused significant losses; but in terms of erosion, the scale of Florence was much less than Fran and Floyd. Because many of the people now on the island weren’t here for Fran and Floyd, they have no experience of the worse conditions that people who have lived there longer have seen.
My point to them was: don’t panic from Florence, from the dune erosion and the beach losses. It’s been worse, and it recovered and you didn’t even realize it.
So was the push a product of that kind of mindset of people wanting a quick fix?
Yes, and I think since they’ve never seen anything that bad before they had no concept on the recovery after those earlier storms. And the rallying cry typically is, “We just want it back like it used to be.” And if you give it enough time, much of it will come back, with the exception of long-term erosion losses. And that means you’ll get back most everything you lost, in most cases, but it might take a while.
So with these perceived threats to the dunes and buildings that people hadn’t seen before — because they weren’t there — they want to do something with all that sand on the beach that’s actually started to already recover after the storm. The beach began to get wider. So the feeling is to go out and pick it up on the lower beach and put it on the higher beach, where you’re more likely to see it at high tide.
Since that’s basically fiddling with the beach profile that’s in this changing state of equilibrium, it’s really a losing battle. If you move too much of it to the wrong spot, the next little storm is going to move it back further offshore.
Was the beach push done, in a sense, to appease people’s perceptions of vulnerability?
It’s been widely used in North Carolina for … forever. When state limits were placed on it beginning around 1978 with the Coastal Area Management Act, it’s been limited in its adverse impact, but it’s also been limited in its benefit.
So Gibson’s description — that it was an emotional benefit — that’s a pretty good description. It makes people feel better; they do better and it looks better, but in terms of significant improvement of the risk to their property or their building, there’s usually little or no significant improvement. We’re just reshaping these equilibrium beaches.
A true benefit is adding sand to the system, like beach fills from dredging or the truck-haul projects. These operations add sand to the equilibrium and move the shoreline away from threatened buildings. And they’re building dunes that wouldn’t otherwise exist.
So sand from outside sources is a much better alternative if you’re going to spend some money on something, rather than simply rearranging the shape of the beach, which is often just a temporary fix. Beach bulldozing or beach pushes are often used after chronic erosion events. You don’t even get weeks’ worth of protection; it goes away before the next significant storm hits.
Source: portcitydaily.com
