Hawai‘i has experienced numerous destructive tsunamis and the potential for future inundation has been described over the years using various historical events and scenarios. To support tsunami preparedness and risk-reduction planning in Hawai‘i, this study documents the variations among 91 coastal communities and 4 counties in the amounts, types, and percentages of developed land, residents, employees, community-support businesses, dependent-care facilities, public venues, and critical facilities in a composite extreme tsunami-inundation zone associated with two great Aleutian moment magnitude (M_w) 9.3 and 9.6 earthquake scenarios. These earthquake scenarios are considered to provide the maximum tsunami scenario for the Hawaiian Islands. According to 2010 U.S. Census Bureau data, the Hawai‘i extreme tsunami-inundation zone contains approximately 248,749 residents and 91,528 households (18 and 20 percent, respectively, of State totals). The residential population in tsunami-prone areas is racially diverse, with most residents identifying themselves as White (47 percent of the total exposed population), Asian (48 percent), or Native Hawaiian and Other Pacific Islander (29 percent), either alone or in combination with one or more other races (note that race categories do not sum to 100 percent because individuals were able to report multiple races in the 2010 U.S. Census). A total of 50,016 households are renter-occupied, making up 55 percent of total households in the extreme inundation zone. The extreme tsunami-inundation zone contains 18,693 businesses (37 percent of State totals) and 245,827 employees (42 percent of the State labor force). The employee population in the extreme tsunami-inundation zone is largely in the accommodation and food services and retail-trade sectors. Although occupancy values are not known for each facility, the extreme tsunami-inundation zone also contains numerous community-support businesses (for example, religious organizations and markets), dependent-care facilities (for example, child-day-care facilities and schools), public venues (for example, colleges and entertainment venues), and critical facilities (for example, fire stations and electric companies).

Community exposure to tsunamis in Hawai‘i varies considerably—some communities may experience great losses that reflect only a small part of their community and others may experience relatively small losses that devastate them. Among the 91 communities and 4 counties, Urban Honolulu has the highest number of people and businesses in the extreme tsunami-inundation zone, and Hanalei has the highest percentages of its people and businesses in this zone. Urban Honolulu has the highest combination of the number and percentage of people, businesses, and facilities in the hazard zone. This report will further the dialogue on societal risk to tsunami hazards in Hawai‘i and help identify future preparedness, mitigation, response, and recovery planning needs within coastal communities and economic sectors of the State of Hawaii.