Whatcom County Council wants to start a dialog on landslide hazards and I was asked to make a presentation. The following are the images from the presentation with just a few notes. John Thompson, geologist with Whatcom County Public Works River and Flood and Natural Resources will present some information as well. A strength Whatcom County has had has been staff geologists that have played a role in reducing hazard risks.
I decided to start the talk with a brief overview of the Oso/Hazel Landslide with some emphasis on the fact that this slide risk was well known by geologists and was foreseeable.
Snohomish County Geohazard Map
LiDAR of Oso area landslides showing age relationships of past large slides
State DNR checked the slide after a storm event in 2009
Most comparable Whatcom County slide to Hazel is the Clay Banks
Recent river blocking slide at Clay Banks
Block of clay showing run out extended beyond current river
LiDAR of Clay Banks and Nooksack River impingement
Aerial of Clay Banks area
This small collapse of an old logging road traveled over one mile
Bark stripped off tree at upper end of failure
Slide mobilized large boulders and wood in debris flow
Home damaged by debris flow/flood
Boulders, logs and mud from debris flow
Small shallow slide in big leaf maple dominated forest
Damaged home from slide
Another slide down small stream
Directly aimed at home
Lifted from Dart's paper on rock failure in New Zealand
Rock failure above the Skagit River in Whatcom County
Damaged truck and dock
Swift Creek Landslide
Fracture scarp on upper Swift Creek Landslide
Bald Mountain Slide in Canyon Creek watershed includes most of the forested slope
Picture taken from a vantage point on another deep-seated landslide
LiDAR of lower Canyon Creek
Bedrock deep-seated failure in Jones Creek above the town of Acme
Upper part of slide with trees on slide
Assessing the passage of a debris flow on Jones Creek
DEM of massive Church Mountain Landslide
Slide is approximately 2,000 years old
Town of Glacier is built on slide
Bedrock landslide on unknown age near Kendal
Staring point of conversation
LiDAR and property lots from Jefferson County Parcel Search web page
Potential landslide risk hazard maps
Screen shot
A popular quote for geohazard types
Outstanding presentation! Hope this leads to a meaningful discussion about realistic options. Not only recognizing slides, but the runout zones has to be part of this discussion
ReplyDeleteI am curious about the cliff side in the Lily Point Marine Park in Point Roberts. I have seen in excess of 20 people hanging out below this cliff that seems to be slowly collapsing. Is this at risk for a bigger landslide?
ReplyDeletehttps://www.whatcomcounty.us/parks/lily-point/index.jsp
Showhank - there are hundreds of miles of steep shore bluffs with that risk. But the odds at any given time are very, very low.
ReplyDeleteI have a series of four posts on Lily Point starting with this one:
http://washingtonlandscape.blogspot.com/2012/04/lilly-point-point-roberts-part-i.html