Julie Maxey-Allison | 10th Street
|Photo Julie Maxey-Allison.
Hopefully, we beachgoers are now heeding the warning signs posted on our bluffs and are taking care to keep a distance from possible troubles. Our bluffs are a bit like a petri dish experiment, going through a change from what they were to what they will be in the future, near and far, as their old structure crumbles. Their collapses, more than 10 since August 2018, are documented. What they will become, how fast and to what extent they will erode/recede is in motion but not yet clear. What is: the bluffs are being assaulted from the rising sea to the West and runoff from resident and rain water to the East weakening their basic stability.
A scientist speaks: from an interview with Dr. Adam Young, of the Integrative Oceanography Division, Scripps Institution of Oceanography. He is Project Scientist for the Statewide assessment of California cliff erosion and retreat.
Q: What is your expectation for the near and far future of the bluffs?
A: As long as waves continue to erode the bottom of the cliffs, the cliffs will remain unstable and retreat.
Q: Can Del Mar take any actions that might help stabilize the bluffs? If so, what?
A: Strategies to reduce wave erosion of the cliffs include maintaining a wide beach with sand replenishment.
Q: Where would Del Mar find such sand?
A: Usually the sand is from either locally offshore or from local lagoons, San Diego bay, etc.
Q: How does it get transplanted?
A: Sand is usually pumped on to the beach from offshore.
Q: How long might imported sand last?
A: It depends on many factors including the sediment size, volume of sand, wave conditions, etc.
So, on your beach walk minimize your risk from our transiting bluffs, outlined by Dr. Young. Look up and out for vertical and undercut cliffs, cracking in the side of a cliff or water from irrigation runoff or rain seeping out of the cliff—all warning signs of instability. These areas are more likely to collapse. The taller the cliff, the more risk. If you spot a recent landslide, know that it can continue to slide over a period of days or even weeks.To keep your distance from danger, walk at low tide when the beach is wide.