Risk of Floods Induced by Dam Break and Possible Restrictions to Land Use on the Floodplain (PAP014923)

Código

PAP014923

Autores

Lígia Maria Nascimento de Araújo, Alexandre Anderáos

Tema

Flood resilient societies through community preparedness

Resumo

The National Dam Safety Policy in Brazil (NDSP) defines obligations and procedures to be followed in order to guarantee standards of safety for dams so to minimize accidents and their consequences. The classification of a dam as high, medium or low hazard is required in order to verify if it should be within the scope of the NDSP, as an alternative criterium to minimum height and capacity. Classification of a dam is a mandate for the regulating agency in charge of the surveillance of its safety. The lack of appropriate basic data such as topographical maps in adequate scale and insufficient information on dams technical characteristics require a great effort of overcoming difficulties and much creativeness to substitute methodologies and finding proxy parameters and criteria. An example of floodplain inundation risk assessment is performed for an existing dam on Preto River a tributary of Piabanha River in the state of Rio de Janeiro, Brazil. The Preto River basin was affected by an extreme rainfall event in 2011 which caused serious damages to the inhabitants and the environment. During the event the reservoir may have attenuated the catastrophic flood peak in safe conditions for the dam. In this work the incoming flood in response to the rainfall event is estimated as well as its attenuation as the flow is routed through the reservoir. The outflow and downstream stages are compared to the flood that could have configured the result of the dam break during a sunny day and also to the circumstances of the natural flow that would have occurred if there was not the dam at that point of the river. Some considerations are presented on restrictions to the floodplain occupation in order to minimize consequences of natural or human induced disasters.