Metodologias para a elaboração de planos de ações emergenciais para imundações induzidas por barragens: estudo de caso: Barragem de Peti-MG

Abstract

The present study aims at preparing Emergence Action Plans (EAP) in order to avoid or to reduce the damages caused by dam breaks by taking into consideration the revision of national and international methodologies. This approach was applied to the case of the Petidam, located in the Santa Bárbara river, Piracicaba Rivers watershed, in Minas Gerais. The concrete-made, arch type dam is located in São Gonçalo do Rio Abaixo town the crests total length is 85,00 m and the maximum height above the foundation is 40,00m. The mappingstudy of the floodable areas was made through 79 km on the Santa Bárbara and Piracicaba rivers crossing the cities of São Gonçalo do Rio Abaixo, Nova Era and João Monlevade. Theupriver from the urban areas and towns of São Gonçalo do Rio Abaixo and Nova Era. The risk management is constituted by four cyclical phases: mitigation, preparation or readiness, response and recuperation. The EAP is a non-structural measure of risk mitigation that has to be prepared in a phase previous to the impact resulted from a flood in order to face up to the risk imposed by the dam on the valley. It consists of five components: detection, taking decisions, notifications, alert/warning, and evacuation. In a valley habited in a river downstream (valley-dam system), the three first components are the dam owners responsibility, and the last two, the local authoritys. In that sense, it is convenient to elaborate two distinct but integrated plans. An internal one, called Dam Emergency Planning,that has detection elements, evaluation and classification of exceptional occurrences, notification, definition of responsibilities, action planning and mapping of downstream risk. The external one, called External Emergency Plan, is more focused on elements connected tothe readiness, to the population warning and to the evacuation process. For the elaboration of the first one, methodologies from diverse outstanding countries in the area, especially Portugal, Spain, United States, United Kingdom, and Australia, were studied. For the secondone, the focus was on the application of methods proposed by the Brazilian Civil Defense, enriching the work with elements from the international bibliography. From this revision, criteria for the application on the case study were defined. The risk mapping was compiled inflood maps through geoprocessing software ARCVIEW. The necessary data for composing the maps and the plans were obtained at Cemig and from interviews with members of São Gonçalos city hall and of the State Civil Defense.