S-3.1.01, r. 1 - Dam Safety Regulation

Section 18 Disposition versions

2012-09-01

18. The delineation of the area that would be affected by a dam failure and identification of the characteristics of the area are based on a dam failure analysis that includes inundation maps. That analysis, using recognized methods, consists of a detailed evaluation of the consequences of a dam failure by means of an accurate delineation of the affected area and identification of the characteristics of the area. The analysis involves an examination of various dam failure scenarios under normal conditions and in flood conditions. It includes a description of the assumptions and procedures that were used to select the scenarios examined and to determine the dam break flood wave, flood wave arrival times and the extent of the affected area. For scenarios in which the dam fails during a flood, the affected area would be the area that would be inundated due entirely to the dam failure.

If, in the opinion of the engineer in charge, the dam failure consequence category is “moderate”, only rough inundation maps showing the area that would be affected by a dam failure are required. This mapping consists of a rough assessment of the consequences of a dam failure by means of a delineation of the affected area on topographical maps and identification of the characteristics of the area. The mapping is established on basic hydrologic and hydraulic calculations, such as flood flows and breach flows, as well as on a rough analysis of the downstream watercourse profile and cross-sections. For the purposes of the mapping, the extent of the affected area is determined by adding the breach flow to the 1000-year flood flow to a point of attenuation or restriction, such as confluence with a large lake or river or another dam.

If, in the opinion of the engineer in charge, the dam failure consequence category is “very low” or “low”, only a characterization of the area that would be affected by the dam failure is required. That characterization consists of a conservative estimate of the consequences of a dam failure by means of a rough delineation of the affected area and a general description of the characteristics of the area. For the purposes of the characterization, the extent of the affected area is established by adding the reservoir depth to the 100-year flood level to a point of attenuation or restriction, such as confluence with a large lake or river or another dam.

The dam failure analysis, rough mapping and characterization referred to in this section must be carried out under the responsibility of an engineer.

O.C. 300-2002, s. 18.