Friday, April 17, 2015

Landslide Setbacks Perspective

In doing some work related research associated with some policy/policy implementation I came across an email within a public document from Jon Koloski. I have been working to purge the concept of standard buffers from landslide hazard regulations or what I prefer to call setbacks so as not to confuse landslides with wetland buffers. It was nice to see another like minded geologist on the matter.

"There is not any definitive science that supports a prescriptive buffer of any dimension for separation of development from the edge of a “marine bluff hazard area” or any other type of landslide hazard area. All of the buffers in use today in land use regulatory documents are based strictly on “administrative convenience” and/or on the belief that some measure of a buffer of separation improves safety to the potentially impacted public or to property….T(t)here are myriad factors that influence specific applicable hazard conditions and those vary so much from site to site, that individual investigation is realistically the only way to characterize an appropriate buffer or setback. The County must recognize that generalization simply has to be based on some factor such as administrative convenience". - Koloski, Jon W., LG, LEG, Senior Principal, Co-Founder of GeoEngineers. Email correspondence to Thurston County dated 1/25/2005.


Bernie Housen said...

This is a difficult issue, but one that needs to be worked out. I have a bit of an issue with Jon K's comment as you have quoted him. I think it is fair to say there is a lot of definitive science on rates of bluff erosion, and other geomorphic processes- but what is missing is application of that science to policy questions such as set-backs. Perhaps a first-order answer (using the coastal bluff example) may be that the setback needs to be such that the structure will not likely be undermined/impacted for at least half of its design life- and the likelihood is estimated by average rate of slope retreat?

Other difficult questions that are not defined well by policy are tsunami inundation hazards and setbacks.

Sam Crawford said...

Russian style (you could almost out-run it...)

Dan McShane said...

Perhaps I should have better emphasized that JK was commenting on what would be an across the boards setback distance on all landslide types.

Sam: that slide video was driving us landslide folks crazy as the liveleak site reference was off by a couple thousand miles. The slide took place at Bolshaya Talda, Kemerovshaya, Russia and appears to be a mine tailings failure from open pit coal mining.