Civil and Environmental Engineering Landslides can vary from very frequent localized rock falls and mud flows to rare but enormously large super-landslides such as the one that sent a big chunk of Oahu into the ocean a million or so years ago. Most are natural phenomena caused by various mechanisms such as erosion, material weakening, volcanic eruptions, seismic activity, water infiltration and many more.

As a result of the 1975 magnitude-7.2 Kalapana Earthquake on the Big Island of Hawai`i, for example, “much of the south coast of Hawaiʻi Island slid horizontally towards the ocean and subsided,” according to the Hawaiian Volcano Observatory.

Human actions are also responsible for triggering landslides: Earth cuts made to construct houses, roadways and other utilities, excessive loading caused by buildings and other structures on hillsides, or water seepage from underground pipe systems are among them.

These landslides are of special concern because they are closely associated with high risks to human life and property losses. Peter Nicholson of UH Mānoa’s Department of Civil and Environmental Engineering has recently begun a pilot project funded by $60,000 from the Federal Emergency Management Agency (FEMA) to develop digital maps highlighting potential landslide hazards on the Big Island of Hawaii.

The maps will be based on fundamental slope stability factors such as slope angle, material properties, rainfall intensity and drainage capacity. In cooperation with the County of Hawaii Office of Civil Defense and the State Hazards Mitigation Forum, Nicholson will develop a GIS-based mapping and analysis tool to identify landslide hazards affecting developed areas, roadways and infrastructure.

The results of this study may be used for planning and permitting in areas where landslide potential is significant, and for hazard mitigation and response. The study will utilize available data and historical landslide information, perform slope analysis using advanced tools, and conduct site visits to verify high hazard areas. Once developed and verified, this tool would be available to other locations where similar data exist.

“An obvious benefit is to delineate locations where landslides could directly impact public safety and economic losses and sever (if only temporarily) lifelines, including emergency access, potable water, and electric transmission,” said Nicholson, anticipating that the color-coded maps can also point out locations where more detailed investigations may be warranted. “Our Civil Engineering faculty members are very active in studying natural and anthropogenic hazards,” explained C. S. Papacostas, Professor and Chair. “Peter himself led a national team investigating the failure of New Orleans levies after Katrina and he presented their findings in testimony to the U. S. Congress.”

Submitted by the University of Hawaii

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