Modelling Under Risk and Uncertainty: An Introduction to Statistical, Phenomenological and Computational Methods

1.1 Protection Against Natural Risk

Natural risk, an important concern for industrial or domestic facilities, has triggered an extensive field of risk research for which the ultimate goal is generally the design of protection for infrastructures or the reduction of the level of vulnerability in existing installations. Probabilistic approaches have permeated to a various extent both regulation and engineering practice, for example with regard to nuclear or hydro power facilities. Here are some notable examples of natural risk addressed:

• flood protection,
• maritime aggressions, such as waves or storm surges coupled with extreme tides,
• extreme winds,
• low flows or high temperatures (threatening the cooling of energy facilities),
• extremely cold temperatures, or associated phenomena (ice blocking, . . .),
• seism.

The typical situation is depicted in Figure 1.1. The box called ‘local risk situation’ summarises all phenomena according to which a flood, seism, cold wave or any type of aggression may impact locally on the installation and generate undesired consequences. It is determined both by:

• the natural hazard events (flood, seism, wind series . . .) that constitute initiators of the risk phenomenon;
• the local configuration of the installation, that is its vulnerability depending on the local mechanics of the natural event and its consequences depending on the assets of all kinds that are at stake (plant operation, integrity of equipments, resulting pollution or damage to the environment, ...