Last week, the Homer News looked at erosion affecting residents of Judy Rebecca Court in the Baycrest Subdivision. This week, the causes of erosion throughout Homer and its possible impacts are explored.
Within the past two months, a slide near the end of Saltwater Drive, at the base of Baycrest Hill, sent tons of soil, coal and rocks of varying sizes crashing down onto the beach. With bluff-side residences a short distance from the site, the slide serves as a reminder that erosion in Homer happens on a grand scale frequently.
About a mile to the west, the area below Country Club Estates looks frighteningly like Anchorage’s Earthquake Park, complete with slices of soil that, over the years, have tumbled onto their sides and whose weight is forcing a ridge of soft, marine clay to the surface.
It is, according to geologist Mike McCarthy, reminiscent of the uplift that occurred near the mouth of Diamond Creek in 2009. Bret Higman, a Seldovia geologist, suggested that uplift was the result of a land mass slippage that caused the underground or beach end to rotate up.
Above the Country Club Estates sloughing, an abandoned house balances precariously on the bluff’s edge and a nearby piece of heavy equipment is tethered to another piece of equipment in an effort to keep it from tumbling down the dropoff.
In 2002, when the city and residents of Ocean Drive Loop weighed the pros and cons of constructing a seawall, Dave Schroer, who moved away from the bluff in 1975, said of sea-driven erosion, “You can only slow it down. You can’t stop it.”
In the spring of 2001, the late Joe Lawlor and his wife, Pat, were awakened during the night to what they thought was an earthquake. In the morning, the couple discovered what they heard was their deck and 25 feet of their Saltwater Drive property disappearing to the shoreline below their home. There had been no quake.
The reasons for erosion are numerous, according to geophysicist Geoff Coble of Coble Geophysical Services in Homer.
“Every area is different, even within Homer,” said Coble. “A lot of times when they talk about erosion, they’re referring to surface soils and that includes the vegetative layer and things that are sliding down a bluff. But occasionally we get slumping, especially along the bluffs, of tertiary material that is two to nine million years old.”
Country Club Estates is a good example of how areas differ. On one parcel teeters the abandoned house and heavy equipment. On the neighboring parcel, Kamran Vasseghi’s home appears sound. Before purchasing the property and house in 2007, he was impressed with the solidness of the structure, its 100-foot margin from the bluff and the way it handled earthquakes.
“I thought, oh oh, here comes the ocean, but nothing happened,” he said of the first earthquake he experienced there.
While the weight of the eroding bluff may be forcing submerged clay to the surface on the beach below Country Club Estates and seawater is eating away the shore along Ocean Drive Loop, it was water coming down Baycrest that super-saturated and weakened the Lawlors’ soil.
Coble offered a different scenario to explain erosion along Kachemak Drive.
“There’s an old lake which used to be much bigger and out to sea. Its footprint is exposed in the bluff. Some of the houses along there are located on top of an old lake shore,” said Coble. “People forget about what this all is. You put a road on top, put a bunch of houses around and then forget what it was. … What it was is really important when you’re talking about bluff erosion.”
In 2004, Homer re-evaluated its regulations concerning steep slope development. At the time, Bob Shavelson of Cook Inletkeeper expressed concerns about the dangers of development, specifically in the area of Woodard Canyon, between Karen Hornaday Park and South Peninsula Hospital.
Coble also weighed in on the discussion at the time, noting the soil beneath Skyline ridge, a mixture of sand, clay, volcanic ash, coal and stream deposits, is poorly bound to underlying sediments and subject to “soil creep. … During an earthquake, that could be pretty dramatic.”
A study by CH2M Hill identified the area above Bayview Avenue, South Peninsula Hospital and Karen Hornaday Park as “generally unsuitable for development.”
The steeper the slope, the stricter the current city regulations impacting construction, according to Rick Abboud, the city’s planning director.
“Depending on where a house goes, we’ll look at the site. We’ll look at the slope of the lot and depending on what that tells us, we may restrict the footprint they use or may have to take special measure to mitigate for their disturbances,” said Abboud.
Summarizing the city’s steep slope code, Abboud said, “When the slope is 15-30 percent, you can’t exceed development of 25 percent of the lot. Then for 30-40 percent it’s 10 percent development. Anything greater than 45 percent needs an engineer to tell us it’s not dangerous.”
In June, Judy Rebecca Court residents began experiencing tilting of the Sonatube foundations beneath buildings on their properties, damage done by the structures’ shifting and, for Gee Denton, large amounts of water pouring out of the hillside behind her home. Engineer John Bishop identified the slope of Denton’s property at 30 degrees, not steep enough to require an engineer’s stamp of approval.
While that applies to new construction, when existing structures become threatened by their slope locations, that’s where Dave Northup of Techno Metal Post Alaska gets involved. Much of his company’s work includes foundation repairs.
“A lot of contractors around town say everything leans toward the bay. Almost anywhere we do work and see Sonatubes, even if you can’t see the bay, they tend to be leaning a little bit toward the bay,” he said.
The rate of erosion can be impacted by more than soil conditions.
“Someone has 2,000 gallons of water delivered to their cistern every month. Consider how much that weighs. Then they use the water and it goes into a drain field maybe next to their bluff. Where the water is going is kind of an important question, but we’re just not in the mode of thinking about that around here,” said Coble.
For some areas, such as Kachemak Drive, the loss of mature trees capable of drinking thousands of gallons of water out of the soil also can impact erosion.
“These spruce trees were there, sucking water out of the surface soil that used to be part of a lake bed and then the spruce bark beetles came and killed those, what are you going to do? That water is still there,” said Coble. “Transpiration from plants that are that large does have an impact on the hydrology.”
Coble and McCarthy offered clues of possible erosion for property owners or potential owners. For starters, if you walk toward the bluff and find you are walking uphill, it could be a sign of an upcoming slump, similar to the sloughing at Country Club Estates. Leaning trees or trees whose trunks bend toward the light may signal soil movement. Cracks in the ground, especially following an earthquake, are another sign of instability. One precaution homeowners can take is to ensure water running off a roof doesn’t run straight down beside the foundation where it can “lubricate the ground and accelerate whatever movement might happen,” said McCarthy.
“If you threw in enough things to worry about — earthquakes at the wrong time, heavy rain storms — you could have some real disaster, but so could anywhere,” said Coble. “I don’t go around worrying about that even though it’s a possibility.”
On the other hand, Lawlor wasn’t worrying about the stability of his property before the March 4, 2001, incident.
“I checked back to 1917 and looked at how quickly the land was eroding,” Lawlor said in the March 8, 2001, Homer News, regarding research he did before buying the property 12 years earlier. “At that time, it was losing about a foot a year. We didn’t plan on needing it for more than 25 years, so we figured we were OK. We certainly didn’t think we’d lose it all at once.”
McKibben Jackinsky can be reached at email@example.com.