Not surprisingly, the quality of a beach is closely tied to the nature of its sand. Compared with the talcum-soft strand of Lanikai, Waikiki feels a bit gravelly. Except for the occasional black or green sand, most of Hawai‘i’s beaches are calcium carbonate. But not all carbonate beaches are alike. We tend to think of beaches like Waikiki as coral sand, which is produced by our offshore reefs, but Fletcher says that our sandy beaches aren’t predominately coral; they’re mostly composed of crushed-up hard algae. “There are two kinds of hard algae,” he explains. “There’s encrusting or coralline algae, and the other one is Halimeda, a green plant. When it dies its photosynthetic material goes away and a white sort of disk remains. These are the dominant components of most of our beaches.”
Fletcher and his graduate students have studied the composition of Hawai‘i’s sands closely, and what they’ve found gets right to the heart of Hawai‘i’s apparent poverty of sand. “Kailua sand,” says Fletcher, by way of example, “is 90 percent reefderived carbonate sand. It’s dominated by up to 50 percent coralline algae, which would be that encrusting algae. That’s followed by about 30 percent Halimeda.” The rest is made up of coral fragments, plankton, bits of mollusk shells and tiny amounts of lava. Much of the pulverization of this material is the action of fish and urchins, which points to a painstakingly slow rate of accumulation. “We radiocarbon-dated the sand on Kailua Beach,” Fletcher says, “and found that very little of it is modern. The youngest sand was about five hundred years old; most of it is two to four thousand years old.”
“Figuratively,” he adds, “we see the ‘sand factory’ as sort of adding a teacup of sand a year.” In other words, the sand that we have now is pretty much the same sand we’ve had for millennia. This is why it’s so important to husband the sands of Waikiki.
For Sam Lemmo, all this means that the renewal of Royal Hawaiian Beach is going to be just one episode in an ongoing drama. “The problem is long-term erosion,” he says. “On average we’ve lost about a foot of beach a year for thirty years.” Left unchecked, much of the beach would wash away entirely, much like the section in front of the Halekulani Hotel known as Gray’s Beach.
To keep up with that pace of erosion, experts like Chip Fletcher will have to continue monitoring the flow of sand in Waikiki. The state and the hotels along the beach will have to continue to invest in replenishment, especially in light of rising sea level. Already, Starwood Hotels, the owner of the Moana Surfrider, plans to raise the level of its Diamond Head wing as part of new development. It’s probably too late to move the grand hotels off their dunes, though. And although it might help a bit to remove the groins, Fletcher says that the damage has been done. After all, some of the engineering mistakes in Waikiki are a century old. So to hold onto the beach we have now, every eight or ten years you’ll see someone like Cranston Kamaka mooring a barge out on the reef to dredge for sand.