Geologic Hazards
Pucker-worthy Debris Flow Video
Geologic Hazards
Soledad Mountain Road Landslide Update
Residents of approximately 75 of the 111 homes evacuated after the slide have been allowed back into their homes. The City of San Diego is not wasting any time in determining the cause of the slide. The first of three 100-ft deep exploration shafts was excavated on Friday, and a Forensic Geologist from a firm hired by the City was sent down the hole to observe geology conditions and to locate the actual slip surface. Also, claims of leaking City water and/or sewer pipes prior to the failure have begun to surface. More details in the full post. (Photo by NELVIN CEPEDA / San Diego Union-Tribune)
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Clatskanie Landslide
Dear geo blogger,
My take on this slide is that the old railroad crossing or road crossing that held up the water for the Clatskanie Event on or about Jan 11, was not “put to bed”. The crossing should have been destroyed and the abutments pulled out of the channel. The slide volume and extent of travel of the subsequent debris flows would have been much smaller and shorter.
I served for a year as an ERFO Hydrologist at the Detroit Ranger Station, up the Santiam Canyon from Salem in 1997 and 1998. An about-to-retire civil engineer, Bill Day, used the “put to bed” term and practice. He also said something else that was useful, “it takes trees to be twenty years old or more before their root systems hold back natural landslides. The trees on the reforested property above the Clatskanie debris flow section were not that old.
I agree with Bill Burns and, to reinforce his statements, I like what he said about the recent spate of landslides.
John Rehm
Registered Geologist G1137
Salem, Oregon
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Note: This is a Opinion based on literature (Dryness, c. 1964), my MS Thesis published on the Rutgers University Geosciences website, and professional experience under registered engineer supervision by Bill Day (1997-1998 (just in case OSBGE is reading this)
Put to bed
Thanks for your insights John. I’ve never heard the term “put to bed” before, but I couldn’t agree with you more. And the factoid about tree root systems seems like a very useful rule of thumb. — Randy Post (aka Rockman)