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failure, would have understated the flooding which actually occurred down- stream from Cascade Lake Dam. The warning and subsequent evacuation based upon actual' observations of the flood and its progress downstream, saved many lives. It is not certain that a better job of warning and evacuation would have resulted if a prepub1ished estimation of the hazard area had been available. Deciding who to warn is made more difficult by the fact that persons not initially at risk may place themselves at risk, often subsequent to the warni ng process. Thi s process, termed "convergence' behavior," i nvo 1ves persons moving towards a disaster to observe, help, or seek information about others [24]. A Rocky Mountain National Park ranger moved through Aspeng1en Campground warning those in campsites likely to be flooded. Subsequent to this, an individual outside the danger zone walked down to the river to observe and help and was lost in the flood. Convergence behavior greatly expands the population potentially at risk and makes the jOb of warning the public more difficult, particularly as in the case of Aspeng1en Campground, when officials are not able to say on the scene to warn persons placing themselves at risk. Warning the public. - Once the public to be warned is identified, officials must decide how to warn them. Two critical trade-offs are confronted. Officials must first decide how much time to spend warning each person. This often requires choosing between a full and complete briefing of a few people and a more hurried warning of a greater number,. This choice is made more critical as the time for warning is shortened. A minimum amount of infor- mation !]lust be given to each individual or appropriate action may not be taken. Reducing the time spent with each individual below this minimum in order to contact more individuals is counterproductive, as no action will be taken by those at risk. This critical threshold for information is of course dependent on characteristics of the population being warned, for example the abl1 ity to appreci ate the magnitude of the threat and the general resistance to taking action. . ' In the Lawn Lake flooding, it appears that time was sufficient and resources allocated properly so as to provide warning to virtually all individuals at risk. . This was aided by a number of factors, including general public aware- ness of recent flooding events and a willingness to take action. This kept the amount of time spent warning each individual to a minimum. The second critical decision officials must make concerns the severity or strength of the warning. If a warning is too mild, persons may not take sufficient action to protect themselves. Conversely, if a warning is too severe persons may take inappropriately drastic action, or persons who are not at risk may take action. Choosing the severity of a warning involves estimating the relative costs of making each type of error. Too weak a warning carries the potential for greater loss of lives. Too strong a warning carries the possibility of unnecessarily inconveniencing individuals, wasting time warning more people than necessary, or causing unnecessary fear and panic which may itself lead to injury or death.