The Tsunami Hazard Is Greatest in the Pacific States and Caribbean Territories, but the Potential Impacts Have Not Been Comprehensively Assessed

Tsunamis pose the greatest hazard to the coastal areas of the five states  bordering the Pacific Ocean and U.S. territories in the Caribbean, but for  many of these areas reliable, comprehensive assessments of potential  tsunami impacts on people and infrastructure have not been completed. Some high-hazard coastal areas do not have tsunami inundation maps— the foundation for evaluating potential tsunami impacts on communities— showing the extent to which a tsunami would penetrate inland and flood  communities, while others have maps that may not be reliable. The Coastal Areas of the Pacific United States, Puerto Rico, and the U.S. Virgin Islands Face the Greatest Tsunami Hazards

According to NOAA, the general areas most threatened by both distant and  local tsunami hazards are Hawaii and the west coast states of California,  Oregon, and Washington, whereas Alaska and the Caribbean Islands of  Puerto Rico and the U.S. Virgin Islands are threatened primarily by local  tsunamis, as shown in table 1. According to NOAA, the Atlantic and Gulf state coasts are relatively low- hazard areas for distant or local tsunamis, with few reliable reports of  tsunami waves of any size ever reaching either coast. NOAA’s Center for Tsunami Inundation Mapping Efforts  at its Pacific Marine Environmental Laboratory assists the modelers and  the states in their efforts. Federal Warning Centers Quickly Detect Potential Tsunamis, but Warning Systems Have Limitations

NWS’s two tsunami warning centers quickly detect potential tsunamis and  issue warnings, but the effectiveness of these warnings has been  hampered by frequent false alarms and limitations in the federal systems  that transmit warnings to the local level. Experts warn that false alarms  may generate unnecessary and costly evacuations and cause people to  ignore future warnings. No destructive tsunami  has reached U.S. shores following any of the 16 warnings—primarily for  local tsunamis—issued to states by the warning centers since 1982. State and Local Tsunami Hazard Mitigation Activities Are Under Way, although Implementation Varies Considerably among Locations

The 12 coastal communities in the six at-risk states and territories that we  visited are taking actions to mitigate tsunami impacts through planning,  warning system improvements, public education, and some infrastructure  protection efforts, although the level of implementation varies  considerably among locations. While state and local tsunami mitigation  plans and warning systems have largely been developed, limitations exist  that have raised concerns about their effectiveness. In addition, key public  education efforts have not been consistently implemented in all coastal  communities we visited, and only a few communities have taken steps to  protect critical infrastructure from potential tsunami damage. Local emergency  managers echoed these challenges. Significant Expansion of National Tsunami Preparedness Activities Is Occurring in the Absence of Long-Term Strategic Planning

A significant expansion of federal tsunami detection, warning, and related  activities, as well as the NTHMP, is under way; however, the future  direction of these efforts is unclear because NOAA has not developed  long-range strategic plans to guide them. Some of NOAA’s activities  designed to strengthen the tsunami program are scheduled in a manner  that raises questions about the extent to which they are risk-based. Recommendations for Executive Action

To help improve national tsunami preparedness, we are recommending  that the Secretary of Commerce direct the NOAA Administrator to take the  following six actions: work with the FEMA Director and the USGS Director to create  standardized tsunami loss estimation software to help communities  determine the potential impact of tsunamis and identify appropriate  mitigation actions;  reduce the number of tsunami warning false alarms by (1) completing the  planned expansion of tsunami detection stations, (2) reexamining NWS’s  rules dictating when a warning will be issued and to which areas, (3)  establishing a routine process for other federal and state experts to  formally review and comment on the centers’ use of seismic data, and (4)  setting performance goals to guide improvements; work with the states to conduct periodic end-to-end tests of the tsunami  warning system, including NOAA Weather Radio and the Emergency Alert  System, to ensure the system will function as intended during a tsunami  emergency;  evaluate the TsunamiReady program to determine what barriers, if any,  exist to participation and what modifications are needed to encourage  more high-risk communities to participate;  evaluate the NTHMP to determine what has worked well in the past and  what high priority activities remain to be completed and to help inform  strategic planning efforts, and; develop comprehensive risk-based strategic plans for the Tsunami  Program and National Tsunami Hazard Mitigation Program that consider  input from states and federal partners and include metrics for measuring  progress toward achieving program goals.
Why GAO Did This Study

The 2004 Indian Ocean tsunami raised questions about U.S. preparedness for such an event. The National Oceanic and Atmospheric Administration (NOAA) leads U.S. detection and warning efforts and partners with federal and state agencies in the National Tsunami Hazard Mitigation Program (NTHMP) to reduce tsunami risks. In 2005, Congress appropriated $17.24 million in supplemental funding to enhance these efforts. This report (1) identifies U.S. coastal areas facing the greatest tsunami hazard and the extent to which potential impacts have been assessed, (2) discusses the effectiveness of the existing federal tsunami warning system, (3) describes efforts to mitigate the potential impacts of tsunamis on coastal communities, and (4) assesses NOAA's efforts to develop long-range plans for federal tsunami programs.

What GAO Found

NOAA has determined that the Pacific coast states of Alaska, California, Hawaii, Oregon and Washington, as well as Puerto Rico and the U.S. Virgin Islands in the Caribbean Sea, face the greatest tsunami hazard. The east and Gulf coasts are relatively low-hazard areas. While high-hazard areas have been identified, limited information exists on the likely impacts of a tsunami in those areas. Some coastal areas lack inundation maps showing the potential extent of tsunami flooding in communities, and others have maps that may be unreliable. State assessments of likely tsunami impacts on people and infrastructure have been limited, in part, due to a lack of tsunami loss estimation software, as exists for floods and other hazards. Although federal warning centers quickly detect potential tsunamis and issue warnings, false alarms and warning system limitations hamper their effectiveness. Some state and local emergency managers have raised concerns about false alarms--the 16 warnings issued since 1982 were not followed by destructive tsunamis on U.S. shores--potentially causing citizens to ignore future warnings. Furthermore, limitations in the Emergency Alert System and NOAA Weather Radio All Hazards may impede timely warnings to communities. For example, signal coverage for these two systems is insufficient to transmit warnings to some coastal areas and failure to properly activate them has resulted in warnings being delayed or not transmitted to some locations. NOAA has begun addressing false alarms but, according to agency officials, lacking the states' permission elsewhere, has only conducted "live" end-to-end testing of the warning systems in Alaska to identify problems. The at-risk communities GAO visited have mitigated potential tsunami impacts through planning, warning system improvements, public education, and infrastructure protection, but the level of implementation varies considerably by location. Most of the states and some communities GAO visited have basic mitigation plans identifying tsunami hazards. While all of these locations have multiple warning mechanisms in place, disruptions to key infrastructure such as telephone lines may hamper timely warnings. Furthermore, key educational efforts, such as distributing evacuation maps and developing school curricula have not been consistently implemented. In addition, few states and communities protect critical infrastructure from tsunamis through land-use and building design restrictions. Emergency managers attributed variability in their efforts to the need to focus on more frequent hazards like wildfires and to funding limitations. Furthermore, few communities participate in NOAA's preparedness program, according to NOAA officials, because they perceive the threat of a tsunami to be low. The nationwide expansion of NOAA's tsunami-related activities and NTHMP is under way; however, the future direction of these efforts is uncertain because they lack long-range strategic plans. NOAA has yet to identify long-range goals, establish risk-based priorities, and define performance measures to assess whether its tsunami-related efforts are achieving the desired results.