USGS: Science for a Changing 


Drawing of volcano

The best defense against any natural hazard is education. Residents and public officials should be aware of the hazards in a given area so that they can make rational decisions regarding where to build homes, develop property for commercial use, and locate public facilities. A well-informed public will neither overreact to the hazards nor ignore them.

Photograph of major lava flow 
during the Mauna Loa eruption of 1984
The Mauna Loa eruption of 1984 fed a major lava flow that advanced toward the city of Hilo. (Photograph provided by National Park Service)
Photograph of Wahaula Visitor 
Center overrun by lava flows in June 1989
The Wahaula Visitor Center in Hawaii Volcanoes National Park was overrun by lava flows in June 1989. (Photograph by J.D. Griggs, USGS)

When an area is threatened by a nearby eruption or an approaching lava flow, the hazard to life can be minimized by evacuating people. The repeated evacuation of residential areas near active rift zones comes at a high cost, however, both for the county government and taxpayers and for the people whose property is threatened by lava. For the long term, volcanic hazards can be avoided by land-use zoning that restricts building in the areas of highest hazard.

Photograph of ground cracks 
and landslides caused by magnitude 6.6 Kaoiki earthquake in 1983
The magnitude 6.6 Kaoiki earthquake in 1983 caused ground cracks and landslides on the rim of Kilauea's summit caldera. (Photograph by J.D. Griggs, USGS)

Diverting lava flows by artificial means is a largely untested and costly option for protecting developed areas. Well-placed barriers may successfully divert a short-lived lava flow, but during a longer eruption, keeping up with the sheer volume of lava and the number of flows involved may prove impossible. During the 1955 eruption of Kilauea's east rift zone, barriers temporarily diverted flows from two different plantations, but in both cases, flows on subsequent days took different routes and ultimately destroyed the property.

Although a few attempts at lava diversion have been partially successful elsewhere in the world, such efforts require favorable conditions of topography and property ownership that can rarely be met in a populated area. Artificial diversion of lava onto property that otherwise would have been spared could lead to complex legal problems. Lava diversion, however, is a reasonable option in unpopulated areas where isolated, high-value property is at risk. For example, diversion structures have been constructed in Hawaii to protect the Mauna Loa Observatory, NOAA's atmospheric research station, from future lava flows.

The potential for damage from strong earthquakes cannot be avoided on the Island of Hawaii. The damage could be reduced, however, by land-use zoning that restricts building on or near steep slopes that may fail during earthquakes and in areas underlain by materials that are likely to amplify the ground motion of a strong earthquake. The Island of Hawaii is in Zone 4 of the Uniform Building Code, which requires public and certain types of private buildings to meet structural design standards for earthquake resistance. Information about the Building Code can be obtained from the Hawaii County Building Division of the Public Works Department.

Tsunamis are a potential threat to all low-lying coastal areas of the island. The tsunami risk to new developments can be minimized by restrictive zoning, such as already exists on Hilo's waterfront, and by flood-resistant construction. Since much of Hawaii's coast is already developed, evacuation of low-lying areas in response to tsunami warnings is the only practical option for avoiding loss of life.

More information about the tsunami warning system, evacuation routes, and emergency procedures can be obtained from the Hawaii County Civil Defense.

Photograph of tsunami 
destruction in Hilo, May 1960
Tsunami destruction in Hilo, May 1960. (Photographer unknown)

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Last updated July 18, 1997
Maintained by John Watson