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III. FLOOD HAZARD MITIGATION PLAN A. FLOOD WARNING AND FLOOD RESPONSE 1. Background About 20,000 communities in the United States are vulnerable to all types of flooding, River and flood forecast service is provided to only a small percentage of these communities, a majority of which would expect to have flood crests in 12 hours or more after the causative event. There are literally thousands of communities that are not protected by site-specific flood warning services, All counties receive generalized flash flood watches and warnings through the National Weather Service (NWS). A flash flood is defined as one that occurs in a short time interval (ranging from a few minutes to a few hours) following the causative event. This is the case in the Buffalo Creek burned area, where flooding occurred very rapidly following the July 12th precipitation event. A flash flood watch is issued by the NWS if conditions indicate that flash floods are likely to occur in a designated area, If flash flooding is imminent or reported, a flash flood warning is issued on a county basis. Flash flood watches and warnings provide only limited alerting, and do not provide the specific forecast information communities often need, 2. Flood Warning A local flood warning system is defined as a community or locally based system consisting of volunteers; rainfall, river and other hydrologic gages; hydrologic models or procedures; a communications network; and a community or local flood coordinator responsible for issuing a flood warning, The purpose of a local flood warning system, whether the most sophisticated automated system or a simple manual system, is to provide responsible officials with advance information that can be translated into response actions, According to recent studies (Carter, 1980) of human behavior during flood disasters, the public does not respond directly to warnings, An appropriate "response" refers to protective actions (i.e., evacuation, seeking shelter, protecting property, etc,), The public typically responds to a warning message by 1) attempting to confirm the existence of a personal threat or risk, 2)tuning in broadcast media, 3)comparing different stations to see if similar warnings are being issued, 4)100king for environmental clues such as heavy rainfall or flooded roads, and 5)seeking additional information from neighbors, friends, relatives, or local authorities, Warning messages are most effective when they confirm other sources of alerts or warnings, A warning should advise people about the actions they should take and what they can expect officials and emergency responders to do, It should also encourage people to pass the word to others, especially those least likely to hear the warning and those who might need help, Obviously, a local warning system that provides timely and accurate flood forecasts is of little value unless individuals take protective actions to reduce losses, The response system defines these critical actions. 8