Landslides and hydraulic structures

The paper discusses two types of hydraulic structures: a) Hydraulic canals and penstocks. They are sensitive structures which typically do not tolerate ground displacements. Two cases are described: the Izbor canal and the Pampaneira penstock. A free water surface tunnel in the Izbor canal, was badly deformed by a landslide induced by a distant road excavation performed at a lower elevation. The Pampaneira penstock has survival 60 years of slow creep of a large ancient landslide. In both cases the proposed action to maintain both structures in operation involved a joint consideration of the landslide motions and an analysis of structural modifications and landslide-structure interaction. In both cases, the climate variability was present in the adopted solutions. b) Dams and the associated reservoirs. Dams generate a profound modification of river valleys because of the unloading effect of excavations and the modification of hydmgeologic conditions of extensive areas affected by the reservoir. The dam projects analyzed (La Brena II, Rules, Arenos and Yesa) provide an overview of case-specific situations which required also specific solutions. They are discussed in the paper. There is, however, a common scenario: the attitude to deal with creeping landslide motions. This point is controversial in practice and, in addition, it poses some fundamental issues in landslide understanding. Critical questions are the acceptable creeping velocity and the expected evolution of a creeping landslide. The cases described illustrate the variety of answers given in practice.