Mapping Tornado-Prone Regions for National Building Codes and Standards
Recent tornado outbreaks in the southeastern U.S. dramatically illustrate what is meant by a statement in the National Building Code of Canada that “tornado hits account for the greatest incidence of death and serious injury of building occupants due to structural failure.” Although life-saving “tornado proofing” structural measures were first introduced into the National Building Code of Canada in 1995, Environment Canada was not yet able to develop the required tornado-prone maps. This meant that the safety measures in national codes and standards could not be widely implemented.
With incremental resources from Environment Canada’s Clean Air Agenda-Adaptation Program and support from Meteorological Service of Canada, the Atmospheric Science and Technology Directorate has now successfully developed maps of “tornado prone” regions. This work involved: detailed investigation and updating of severe thunderstorm events with damaging wind reports; development of a new national Tornado Database; analyses of the results using additional guidance from lightning and population density data; a climate-engineering investigation of tornado-proofing requirements in codes and standards from many countries; and determination of relevant and significant tornado “thresholds” that could be linked to the National Building Code of Canada measures.
The maps have been submitted to the National Building Code Commission and will be used to implement the life-saving measures in the National Building Code of Canada and Canadian Standards Association standards for school mobiles, manufactured homes, and block wall construction.
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