SENAT
Report n° 117 (2007-2008) by M. Roland COURTEAU, Senator (for the parliament office for the evaluation of scientific and technological choices) - Appendix to the minutes of the 7 December 2007 session
Disponible au format Acrobat (21 Moctets)
(2) A national plan to limit the impact of tsunamis
While the risks run by Hawaii in the event of a tsunami have long been known, it is only rather recently that the states of Washington, Oregon and California are also recognized as being vulnerable.
An earthquake in the Cascades subduction zone 15 ( * ) in April 1992, which provoked a tsunami in northern California, underlined the shortcomings of the warning system. On 4 October 1994, a Pacific-wide tsunami warning was issued following a strong, tsunami-generating earthquake in the Kuril Islands. In the United States, this event provoked enormous confusion between the various emergency services, resulting in the costly evacuation of Hawaii which drew sharp criticism when the warning turned out to be false.
To remedy this situation, Congress decided to launch in 1995 the National Tsunami Hazard Mitigation Program (NTHMP) under the direction of the NOAA and covering both the coastal states and America's island protectorates.
This programme relies on three main lines:
- tsunami evaluation: a better understanding of past tsunamis will produce more refined inundation maps based on long-term tsunami forecasting;
- the quality of the warning system, through the improved collection and processing of seismic data, the deployment of a network of tsunami-detection buoys, and a better transmission of the warning information to the competent authorities;
- preventive measures, via the early elaboration of prevention and evacuation plans, as well as the development of educational materials to help raise public awareness.
Taking into account the subsidiarity rules linked to federalism, a close partnership has developed between the federal, state and local authorities.
In addition, the NOAA launched a programme entitled "TsunamiReady", which encourages the at-risk communities and states to adopt those measures necessary to effectively mitigate the effects of a tsunami.
Based on the principle of voluntary participation, this programme sets the criteria which must be respected in order to earn this label, including:
- establishing a 24-hour warning point and emergency operations centre;
- have more than one way to receive tsunami warnings and alert the public;
- increase public awareness through the distribution of information and community education;
- develop a formal tsunami plan, which includes holding periodic emergency exercises.
To this day, 47 sites 16 ( * ) (cities, counties, beaches, harbours) in 10 different states have earned this label. Hawaii is the only state considered "tsunami ready".
In addition, following the devastating Sumatra tsunami, the President of the United States proposed a $37.5 million package to improve the national warning systems. In May 2005, the Emergency Supplemental Appropriations Act was passed, which granted an additional $17.24 million to the NOAA in order to extend and improve its tsunami-detection capabilities, to make the warning centres more effective, to produce inundation maps and to extend the TsunamiReady programme to all coastal states. A new law was passed in August 2006 to extend the NOAA's budget from $25 million in 2008 to $29 million in 2012.
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The mixed assessment of the National Tsunami Hazard Mitigation Program (NTHMP) by the Government Accountability Office (GAO) The GAO is an independent, non-partisan agency that works for the American Congress. With a staff of 3,260, a budget of $484.70 million and 11 offices scattered around the United States, its mission is to monitor the use of public funds and evaluate federal programmes and policies. Between April 2005 and March 2006, the GAO studied the National Tsunami Hazard Mitigation Program (NTHMP) and afterwards issued a rather mixed assessment of its actions. 1. An incomplete evaluation of the risks The GAO remarked that in those states and territories at risk (Alaska, Washington, Oregon, California and Hawaii for the Pacific zone, Puerto Rico and the Virgin Islands for the Caribbean), numerous regions either had not established inundation maps, or depended on unreliable documents, even though the NTHMP had planned on furnishing updated inundation maps to all at-risk communities by 1999. The GAO also criticized the absence of any detailed forecasting concerning the loss of human life and damages to infrastructure, government and vital installations (power stations, hospitals, telecommunication networks, etc.). It pointed out that computer programs already existed for quantifying the damages caused by other natural disasters (inundations, tornadoes, earthquakes) and urged the NOAA to develop a similar program for tsunamis. 2. A poorly-calibrated warning system In addition, the GAO criticized the number of false warnings issued by the Hawaiian and Alaskan centres. While it applauded the decreased delay in the sending of warning bulletins, it nevertheless pointed out that since 1982, all 16 warnings announcing a destructive tsunami for the American coasts proved to be false. However, these false warnings damage the system's credibility and prove quite costly: the evacuation of Hawaii in 1994 cost an estimated $58.2 million (in current terms). The GAO also estimated that the list of regions receiving initial warning messages was too long and did not take into account their geographic distance from the event, which allows for more refined forecasting during the tsunami's propagation. 3. Shortcomings in the warning-transmission system The GAO discovered technical malfunctions in the transmission of messages. It pointed out that the warning centres transmit their messages to the forecasting services of the National Weather Service, which then transmits them via the NOAA's weather radio and the "emergency broadcast system". The NOAA's weather radio is a 24-hour, nationwide network of radio stations that continuously broadcasts weather information, including warnings of natural risks. The emergency broadcast system is a means of communication that was originally reserved for the President of the United States, allowing him/her to directly address the public in the event of an emergency. This system can also decode and retransmit warning messages emitted by the NOAA's weather radio via the network of radio stations and television channels, as well as by cable. However, the GAO discovered that certain coastal towns were unable to receive information sent out by the NOAA's weather radio and/or the emergency broadcast system. It therefore recommended that the entire information-transmission chain be tested. 4. Weaknesses in the tsunami-prevention system The GAO investigated the effectiveness of those prevention systems which rely on the telephone network, such as sirens without satellite transmission and Internet-based warning messages. These infrastructures would be out of service in the event of a strong earthquake. In any case, past experience shows that they would be saturated immediately after the first warning message, which can compromise communications between the various services in charge of civil security if they do not have satellite phones. In addition, the GAO emphasized the necessity of carrying out training exercises to uncover any weaknesses in the system, citing as examples the often underestimated evacuation time and problems related to traffic control (certain access roads can become inundated and therefore unusable). 5. An inconsistently-informed public The GAO observed that few regions at risk had verified that their populations were indeed aware of the existence of evacuation plans, either through their generalized distribution or their insertion in the phone book. Likewise, raising tsunami-awareness among school children and the carrying out of evacuation exercises varied greatly from state to state. 6. Urban planning that ignores the tsunami risk The GAO criticized at-risk regions for not taking into consideration tsunamis in their urban planning. Oregon is the only state to have set limitations on the construction of dense residential complexes in areas prone to inundationing. 7. Questioning the extension of the national tsunami mitigation programme's range of application The GAO questioned the usefulness of extending this prevention programme to regions little or not at all concerned by tsunamis, such as the Atlantic coast and the Gulf of Mexico, and feared a too-thin spreading of the budget to the detriment of those zones really at risk. After observing that local tsunamis represented the greatest risk for most regions of the United States, it questioned the NOAA's strategy to extend the network of DART buoys and improve the effectiveness of the warning centres, when, in fact, teaching the public the right reflexes (such as seeking refuge on higher ground in the event of a strong earthquake) should be a priority. In conclusion, the GAO regretted that the programme's effectiveness had never been evaluated before the decision to extend the programme had been made. No study had been carried out on the effectiveness of the education and public-awareness programmes and no assessment had been made concerning the system's strengths and weaknesses. Source: Government Accountability Office |
* 15 This zone is located off the coasts of Washington, Oregon and California.
* 16 Out of an eventual 500 sites.