Landslide Hazard Susceptibility Mapping in Homer

The Alaska Division of Geological & Geophysical Surveys published landslide hazard susceptibility mapping for the City of Homer and Kachemak City.

The publication is available for purchase or free download on the  Alaska Department of Natural Resources Geological & Geophysical Survey webpage and includes:

• an Executive Summary
• an inventory and map of existing slope failures
• maps that show areas potentially susceptible to shallow and deep-seated landslide susceptibility, and
• a map of simulated debris flow runouts for the City of Homer and Kachemak City.

To develop the maps, the Division of Geological & Geophysical Surveys (DGGS) looked at known historical landslide data, and considered soil properties and the steepness of slopes measured by LiDAR or (Light Detection and Ranging) system. 

DGGS developed the maps using the best available data at the time of their study; however, conditions that actually lead to a slope failure or landslide are complex.  Some factors like vegetation, soil structure, heavy rainfall, snow melt and changes in ground water levels change at different rates, while other landslide triggers, like earthquakes, are unpredictable.

As such, the maps in the publication do not predict slope failures, but depict locations where landslides have occurred and where additional geotechnical investigations are suggested should the area be developed.

DGGS is dedicated to mapping and assessing landslides, understanding and quantifying landslide hazards, and improving geologic hazard communication and coordination with other agencies and communities. Results are intended to educate officials and the public regarding locations of potential slope failure hazards and provide a basis for regional, long-term planning and resilience.

DGGS’ Homer and Kachemak City Landslide Hazard Susceptibility Study was funded by the Federal Emergency Management Agency (FEMA) Cooperating Technical Partners program.