1998 Kelso, Washington, Landslide1998 Kelso, Washington, Landslide• Second largest suburban landslide in U.S. history• Exceptionally unstable geology

– Troutdale Formation overlies Cowlitz Formation• The contact is a potential failure surface

• FEMA-funded buy-out– 137 homes damaged to some extent– 127 homes to be purchased– Owners paid a maximum of 37.5% of house value

Kelso, WA Landslide: Locator MapKelso, WA Landslide: Locator Map

Kelso, WA Landslide: OverviewKelso, WA Landslide: Overview

Upper Aldercrest: A Down-Scarp ViewUpper Aldercrest: A Down-Scarp View

Upper Aldercrest: Small ScarpUpper Aldercrest: Small Scarp

Upper Aldercrest: A Plumb WellUpper Aldercrest: A Plumb Well

Upper Aldercrest: Hanging DrivewayUpper Aldercrest: Hanging Driveway

Upper Aldercrest: Downdropped HouseUpper Aldercrest: Downdropped House

Upper Aldercrest: Separated SectionUpper Aldercrest: Separated Section

Upper Aldercrest: Part of the DrivewayUpper Aldercrest: Part of the Driveway

Upper Aldercrest: Rotated StructuresUpper Aldercrest: Rotated Structures

Upper Aldercrest: Hanging StructureUpper Aldercrest: Hanging Structure

Upper Aldercrest: Missing FoundationUpper Aldercrest: Missing Foundation

Upper Aldercrest: Separated SectionUpper Aldercrest: Separated Section

Upper Aldercrest: Torn & TwistedUpper Aldercrest: Torn & Twisted

Upper Aldercrest: Separated MasonryUpper Aldercrest: Separated Masonry

Upper Aldercrest: An Abrupt ScarpUpper Aldercrest: An Abrupt Scarp

Upper Aldercrest: Hanging RoofUpper Aldercrest: Hanging Roof

Upper Aldercrest: Tilted Plumb WellUpper Aldercrest: Tilted Plumb Well

Lower Aldercrest: Temporary WaterLower Aldercrest: Temporary Water

Lower Aldercrest: Moderate MovementLower Aldercrest: Moderate Movement

Lower Aldercrest: New Tension CrackLower Aldercrest: New Tension Crack

Lower Aldercrest: Side-Slope ShiftingLower Aldercrest: Side-Slope Shifting

Lower Aldercrest: Detached GarageLower Aldercrest: Detached Garage

Lower Aldercrest: Unwanted SunroomLower Aldercrest: Unwanted Sunroom

Lower Aldercrest: A New EntrywayLower Aldercrest: A New Entryway

Lower Aldercrest: Minor ShiftingLower Aldercrest: Minor Shifting

Lower Aldercrest: Natural “Tea”Lower Aldercrest: Natural “Tea”

Lower Aldercrest: Offset CurbingLower Aldercrest: Offset Curbing

Lower Aldercrest: Lowered BasketLower Aldercrest: Lowered Basket

Lower Aldercrest: Parallelogram ShiftLower Aldercrest: Parallelogram Shift

Lower Aldercrest: Hold-Out ResidentLower Aldercrest: Hold-Out Resident

Lower Aldercrest: Pressure RidgeLower Aldercrest: Pressure Ridge

Lower Aldercrest: New ScarpLower Aldercrest: New Scarp

Lower Aldercrest: Halted ConstructionLower Aldercrest: Halted Construction

Lower Aldercrest: Lateral ShiftLower Aldercrest: Lateral Shift

Lower Aldercrest: Lateral Shift DetailLower Aldercrest: Lateral Shift Detail

Lower Aldercrest: Tension CracksLower Aldercrest: Tension Cracks

Lower Aldercrest: Makeshift RoadwayLower Aldercrest: Makeshift Roadway

Lower Aldercrest: Parallelogram #2Lower Aldercrest: Parallelogram #2

Lower Aldercrest: First Floor DamageLower Aldercrest: First Floor Damage

Lower Aldercrest: A Side ViewLower Aldercrest: A Side View