Risk has many definitions. Here, we will define actual risk as Probability times "Consequence". Consequence also has many definitions. For example, the number of deaths is a consequence, as is economic damage or impacts to the environment. Consider the case of economic damage by storm surge. As storm surge increases, economic damage increases. Yet, as storm surge increases, its probability decreases. So, extremely large storm surges are not typically associated with the largest risk (a number close to zero multiplied by a very large number). Small storm surges likewise are not typically associated with the largest risk (a number close to one multiplied by a very small number).
To illustrate risk, consider Hurricanes Rita (2005) and Ike (2008). Both storms were of similar size and intensity (central pressure) when they made landfall. Both generated similar storm surges. Yet, if both hurricanes made landfall today (2013), Hurricane Ike would cause nearly twice as much damage as Hurricane Rita (ICAT Damage Estimator)*. The reason for this dramatic difference in damage is that Hurricane Rita made landfall along the relatively unpopulated coast at the Texas/Louisiana border, while Hurricane Ike made landfall in the densely populated the Houston/Galveston, TX region. So, while both of these surge events likely have a similar probability, their consequences are very different.
To illustrate risk, consider Hurricanes Rita (2005) and Ike (2008). Both storms were of similar size and intensity (central pressure) when they made landfall. Both generated similar storm surges. Yet, if both hurricanes made landfall today (2013), Hurricane Ike would cause nearly twice as much damage as Hurricane Rita (ICAT Damage Estimator)*. The reason for this dramatic difference in damage is that Hurricane Rita made landfall along the relatively unpopulated coast at the Texas/Louisiana border, while Hurricane Ike made landfall in the densely populated the Houston/Galveston, TX region. So, while both of these surge events likely have a similar probability, their consequences are very different.
*Pielke, Jr., R. A., Gratz, J., Landsea, C. W., Collins, D., Saunders, M., and Musulin, R., 2008. Normalized Hurricane Damages in the United States: 1900-2005. Natural Hazards Review, Volume 9, Issue 1, pp. 29-42.
Acknowledgements & Credits: This material is based upon work supported by the Texas Department of Public Safety's Division of Emergency Management. Background photo courtesy of Mark Moran (Creative Commons license CC BY 2.0)
© 2019 Jennifer L. Irish & Steven M. Quiring. All rights reserved.
Acknowledgements & Credits: This material is based upon work supported by the Texas Department of Public Safety's Division of Emergency Management. Background photo courtesy of Mark Moran (Creative Commons license CC BY 2.0)
© 2019 Jennifer L. Irish & Steven M. Quiring. All rights reserved.