Ken LaJoie: The Coastside Cliffs Were His Beat In 1980, Part I


Geologist Ken LaJoie, the cameraman and I were standing on the cliffs near Surfer’s Beach in 1980. Surfer’s Beach is located across Highway 1 from El Granada, the town founded by the Ocean Shore Railroad. I was interviewing Lajoie as we shot footage for “The Mystery of Half Moon Bayâ€?.

Ken worked for the USGS in Menlo Park and had been measuring cliff erosion on the Coastside for years. These are his comments more than 20 years ago—it would be fascinating to hear what an expert says today—since 1980 there has been a lot of work done in and around the breakwater.

Ken LaJoie’s comments (1980)

“Half Moon Bay is a unique geographical formation where the potential for erosion is very high due to soft material exposed in sea cliff.

“Natural erosion is due to dynamic equilibrium.. After the breakwater was built that very delicate dynamic equilibrium was upset. The waves were refocused on the south side of the breakwater.

cliff.jpgocean.jpgbldg on cliff.jpg

“The sand that was supplied by the cliff erosion north of the breakwater was denied to the beaches to the south.

“Two factors together caused accelerated erosion rate south of the breakwater. Rate cliff is receding between 1957 when breakwater was built and 1971. The highest rates were in order of eight feet per year. From 1971 to present highest rate we measured are around 12 feet were year. As rate continue to erode in area south of the breakwater eventually they’ll be into the highway.

“The erosion will jeopardize the highway.

“Now either the cliff is cemented up or a series of jetties (or groins) will have to be built. No matter what the solution it will probably be a temporary solution. Whatever method used to arrest erosion south of the breakwater itself will refocus the erosion farther south and even today concern that depletion of sand in this region will eventually affect the beaches to the south and that this depletion of sand as it progresses will affect the state beaches, Dunes Beach to the south.

“When the breakwater was built, the Corps of Engineers recognized that there would be a slight increase in erosion south of the breakwater. Small amount of rip rap was placed south of the breakwater to prevent a rapid rate of erosion in that area.

“We can see from where the rip rap is today that it didn’t stop the erosion.

“The photos we took in 1971 show large masses of rip rap which is nothing more than large boulders, large pieces of cement.

“In many instances, here in Half Moon Bay, car bodies placed were placed at the baes of the cliff to try to slow the erosion down.

“In 1971 this rip rap was at the base of the cliff and we can see today that it’s sitting out in the middle of the beach. Very ineffective.

“The waves have attacked the cliff and they’ve eroded back at least 80-100 feet beyond the rip rap…â€?

…To be continued…

Playing At El Granada Beach 1930s

Follow the 1930s bathing beauties at El Granada beach–see the bountiful sand dunes? Today this beach is better known as “Surfer’s Beach”. You won’t find any sand dunes, though….




(From a Chamber of Commerce Promotional Film, 1930s that appeared in my 1981 documentary, “The Mystery of Half Moon Bay”)