Beaches slip-sliding away
By Jan TenBruggencate
Advertiser Environment Writer
Most of Hawai'i's beaches are eroding — some severely — driving government and private interests to a range of shore-saving measures, from building stone and concrete structures to dumping sand in areas to replace what's lost.
Cory Lum • The Honolulu Advertiser
"There is a tremendous amount of beach loss and narrowing in the state," said Sam Lemmo, Coastal Lands Program manager for the state Department of Land and Natural Resources.
Since 1910, Waimea Bay has lapped steadily inland, dramatically eroding the once-wide sandy beach.
Federal officials agree. With a few exceptions, "it appears, overall, that all the beaches are eroding," said Jim Pennaz, chief of the Army Corps of Engineers' Civil Works Technical Branch. Expanding beaches appear to be in a distinct minority, he said.
Coastal erosion surveys indicate that 25 percent of O'ahu's sandy shoreline and a third of Maui's beaches have disappeared because erosion during the past 80 years, said Charles "Chip" Fletcher, geology professor at the University of Hawai'i.
"I believe those numbers are valid," Lemmo said.
Across the state, desperate landowners are building illegal seawalls, or seeking permits for walls. Some landowners are installing emergency sandbag walls. Others are quietly having boulders dropped on the shore. Some are dumping sand on their shorelines — saving their beaches, but at considerable cost.
Decades ago, concrete seawalls were the standard form of shoreline protection. In some situations, rock groins have built into the sea to reduce current flow and protect sand. Examples of both can be seen at Waikiki Beach. In other areas, agencies have built structures ranging from concrete-walled basins to sloping revetments of huge boulders.
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The County of Kaua'i got into trouble with the state and federal governments for trying to protect the shoreline by dumping scrap concrete rubble onto the beach fronting the Wailua Golf Course.
But there are severe differences of opinion on how well these "hard" structures work. Many argue that they don't work at all, and may even increase erosion. Others say they work, but to protect the property behind the wall, not the beach in front of it.
The beach preservation action that has had the most support lately is beach replenishment — or dumping sand on an eroding beach. But it is not a permanent solution. At Lanikai, where government and landowners have dumped a great deal of sand, erosion continues. Same along the Kihei coastline on Maui.
"If you build a project where you need beach replenishment, you're committing to a long-term cost," said the Corps' Pennaz. That's because sand will need to be dumped on those beaches repeatedly.
One thing that's increasingly clear is that the old technology of dumping rocks or building concrete or stone walls does not save beaches. It creates a fortified shoreline.
"Walls do not preserve beaches. Walls destroy beaches," Lemmo said.
The Corps of Engineers, which designs many coastal structures, suggests a properly designed revetment should not promote erosion, but concedes that in a situation where erosion is active, it will do little except protect the land.
"There are situations where a hard structure may be the only solution, or the best solution," Pennaz said. He cites situations on Kaua'i, O'ahu and Maui where coastal erosion has threatened to destroy coastal highways. Rock protection has worked to preserve roads, he said.
Seawalls thus can save the property they're protecting, but at the cost of the sandy shoreline, and sometimes at the cost of erosion on neighboring properties, said Fletcher, who is considered the leading scholar on the subject of coastal erosion in Hawai'i. "Erosion is a lack of sand, and no structure makes up for a lack of sand," Fletcher said.
Lemmo said it's important when considering coastal erosion processes to distinguish between two key features: coastal erosion and beach loss.
A beach is a dry sandy area between the water and the coastal vegetation. In a normal erosion event, the beach migrates inland, but a dry sandy beach survives between the water and the vegetation. A concrete or rock wall or revetment can prevent further erosion of the inland property, but it also destroys the beach. The water ends up lapping right at the base of the rocks or concrete.
That leaves no white sand beach for sunbathing, beach volleyball, sunset walks and scenic photography.
Not all Hawai'i beaches are eroding, and a few are actually getting wider. Kailua Beach gained sand for close to a century while neighboring Lanikai was losing it. But for the past 12 years, the trend at Kailua has been erosional. It is not yet clear whether this is a temporary or permanent shift, Fletcher said.
Fletcher said there are three fundamental causes of beach erosion:
• Waves and current move sand, normally seasonally. Some beaches are wider in winter than summer and some are the other way around.
• Rising sea levels cause beaches to migrate landward.
• Human interference can be a major factor. People have mined and bulldozed the dunes around the Hawaiian archipelago that beaches once used as sources of sand during natural erosional periods. People have hardened shorelines with rocks and walls that promote erosion. Humans have dredged shoreline areas and hauled sand off beaches for road construction, for landfilling, for making concrete, and for agricultural purposes.
Waimea Bay on O'ahu once had a much wider sandy area than today. In years past, officials believe the sand was mined regularly, removing much of the available beach volume. Now the mining has stopped, and so has the inland migration of the shore.
"Waimea beach is stable now. It's not eroding," Fletcher said.
Many researchers feel the least destructive means of stopping landward migration of beaches is to put sand down, although sources of clean sand are hard to come by. The process, in essence, replaces the sand that has been removed over time by humans.
Sand is being placed on beaches in Waimea, at Kikiaola, and Po'ipu, at Brennecke's Beach, on Kaua'i; at Mauna Lahilahi, Waikiki and Lanikai on O'ahu; and at Spreckelsville, Ma'alaea and Kihei on Maui.
In a few places, officials hope to combine sand replenishment with hard structures, such as a proposed breakwater off the Makaha Surfside condominium near Mauna Lahilahi Beach Park, which is designed to reduce wave energy that erodes the shoreline.
Some of the most extensive efforts are being made at Hawai'i's landmark beach, Waikiki. Lemmo said there is money in the coming year's state administrative budget to pump to Kuhio Beach sand from a reservoir 2,000 feet from shore and 10 to 20 feet deep.
"There's a big sand field out there," Lemmo said.
A small-scale test pumping in 2000 from the same sand field yielded sand that was slightly darker in color than normal beach sand, but which became almost indistinguishable from normal beach sand after being blended with regular sand.
If next year's project is successful, it will be the first major pumping operation of its kind in the Islands.
But Fletcher said it might be better for the state to select its most important beaches, and let natural erosion processes have their way. No formal proposal has been developed, but he and Lemmo have discussed designating Hawai'i's "legacy" beaches, and buying up the coastal land, so the sand can ebb and flow normally.
Kailua Beach is an example of a classic legacy beach, Fletcher said. It is huge, beautiful and it is well-used for all kinds of water activities. He says it's time for Hawai'i to bite the bullet and agree that the beach is more important than beachfront homes.
"We fundamentally have not guaranteed the safety of any beach. We have not guaranteed that our grandchildren will have a Kailua Beach," Fletcher said.
Ultimately, if Hawai'i develops the political will to decide that its beaches are crucial, "no one will be permitted to stop the natural erosion of the shoreline. Homes will have to be sacrificed," Fletcher said.
