On a warm summer evening, the earth gave way and half of a beautiful resort home fell into the lake:
Was it caused by a geological fault? Were other homeowners in danger?
The event also caused a large, deep crack at the surface, north of the house, close to another residence.
The crack continues to the left and is visible downward (i.e. left) face of the cliff. At the top right, some of house's foundation remains. The remains of the house were set on fire. What was left after that was pushed into the lake. Note the debris accumulated at the water's edge, on an erosion-resistant limestone shelf.
We acquired, processed, and analyzed high-resolution satellite data, historical air photos, maps, government data, peer-reviewed articles, and conducted field work and interviews.
Our analysis revealed:
These days, the river continues its active, strong, and persistent flow whether the lake level is high or low: its turbidity and wave action nudges away the cementing properties that holds together the horizontally-oriented rocks—in particular the interbedded limestone and shale—that make up the cliffs. In time, larger and larger rocks are shed. Support for the rocks and the soil above is undermined.
This is how the river looked a few years before it was covered by the lake. The eventual location of the house is shown in red, on the cliff (which is the prominent white, linear feature that extends from the lower right edge of the photo to the top middle).
U.S. Geological Survey map shows the river channel (dashed line), today's normal lake level (blue), the "full" level (light blue) and the house location (in red) on the cliff face.
Lake water levels fluctuated 61' over the years. The water level shown in the above picture is 521' ASL. The highest lake level has been 570.25’ ASL.
The record of lake level changes.
The remaining part of the house in place above the cantilevered cliff face. The tension crack is visible in the extreme lower right.
Four years after the initial cliff failure, the northern part of the cliff fell during a five inch rain event with wind speeds of 47 mph.
"Before" shows the cliff before it failed. The house, retaining wall and garden are intact. "During" shows the south half of the cliff gone and the tension crack as it trends NNW; the "After" image is four years later, after the northern half of the cliff fell off into the water, unattended by a seismic event.
David G. Koger is a Remote Sensing Image Analysis expert with over 40 years of experience in the field. A Vietnam Era Marine Corps veteran, he configured and operates a state-of-the-art remote sensing image analysis and geographic information system and consults on various remote sensing applications. Mr. Koger offers Forensic Digital Image Analysis of remotely sensed, aerial photo (digital or film), and underwater video. His services include forensics, time-series studies, and documentation of surface damages, wildfires, material movements. Expert witness strategies and research methodologies are available to attorneys representing plaintiff and defendant.
©Copyright - All Rights Reserved
DO NOT REPRODUCE WITHOUT WRITTEN PERMISSION BY AUTHOR.