Simplified seismic safety evaluation of existing small gravity dams

A seismic safety assessment is routinely performed for new dams, regardless of their size. With increasing frequency, this is also done for large existing dams. However, many existing small dams still lack a comprehensive evaluation of seismic safety. The latest change in the Swiss dam safety legislation requires a seismic safety evaluation of small dams over the next few years. As the number of small dams exceeds the resources of both authorities and owners, the Swiss Federal Office of Energy (SFOE), as the national dam safety supervisory authority, has developed an approach which allows for a simplified stability assessment for a ‘first-stage’ seismic safety evaluation of existing small gravity dams. Because of its ease of application, the approach can be a valuable tool for the assessment of large numbers of gravity dams. The assessment can then serve as the basis to determine which structures should be prioritized for investigation in greater depth. The approach presented here has recently been introduced into the Swiss directive on dam safety.