As often happens this time of the year, sand at Baldwin Beach Park is being washed away, creating steep dropoffs on the beach and exposing tree roots along the Paia shoreline.
The culprit is the typical summer trade wind swells that push the sand at the park from its east end in the vicinity of the old lime kiln site toward "Baby Beach" at the far west end, said University of Hawaii Sea Grant Extension agent Zoe Norcross-Nuu.
Norcross-Nuu said the process occurs during the summer, but the extent of the coastal erosion is more noticeable at the end of the summer as the bulk of the sand has had months to migrate down the shoreline.
Stumps of trees that were cut down mark the extent of the beach loss in 2006. This summer’s erosion is threatening trees that survived. Marine specialist Zoe Norcross-Nuu said coastal erosion at Paia is the result of trade wind-driven swells pushing sand from the east end to the west end of the beach.
The Maui News / MATTHEW THAYER photo
"It will pretty much keep eroding until we get our first big northwest swell," she said.
County Deputy Parks Director Zachary Helm said caution signs have been posted to warn beachgoers of the steep drops and park personnel were discussing whether to put up temporary plastic orange fencing to block beachgoers from the most severely eroded sections.
As of Wednesday afternoon, no areas had been closed.
"We're monitoring it as we speak," Helm said.
He cautioned that beachgoers need to be aware of their surroundings and asked that people not walk on the eroded dunes during high tide, when wave action is heaviest.
"We just want to inform the public to take extra caution. It's Mother Nature that's working, it's something we have no control over."
Helm said parks officials along with County Arborist David Sakoda have inspected the beach and the threatened trees. He said the county has been monitoring the situation since last week.
On Wednesday, several trees were precariously close to toppling, while the eroded shoreline was approaching the park restroom.
The beach was severely eroded two years ago, when trees and an outdoor shower were downed and the lifeguard tower was damaged. A new lifeguard tower is on skids, allowing it to be pushed away from the shoreline when severe erosion occurs.
But the restroom and lifeguard storage building that was nearly undermined in 2006 is threatened again.
Norcross-Nuu said that by November or so, the sands should be shifting back to the east end of the beach with the northwest winter swells.
Although the sand will eventually return to the beach, some of it will be lost.
"Each year the beach comes back, it's coming back a little less," she said.
According to the UH erosion maps, Baldwin Beach Park is losing 5 feet of beach each year, the highest of any sandy beach on Maui, Norcross-Nuu said. She said frequent beachgoers and lifeguards suspect the beach is losing even more footage annually.
She pointed out the lifeguard tower at Baldwin had to be moved back several times because of the eroding beach, but it never has been pushed forward.
Norcross-Nuu said there are several reasons Baldwin Beach Park is susceptible to the seasonal conditions, including the prevailing current and strong onshore winds. The entire shoreline was damaged as well when sand was mined at the Paia lime kiln beginning in the early 1900s. The sand was roasted by the sugar plantations to provide a calcium-rich soil amendment.
* Melissa Tanji can be reached at firstname.lastname@example.org.