PAR is not Risk. Why Proxies Don’t Work.

ABSTRACT ONLY - As the dam and levee safety community moves toward the application of risk informed decision making (RIDM), we should be sure to appropriately apply the principles and tools. It’s important to be aware of two issues that often come up when trying to simplify the effort: 1) Hazard classification is not the same as life safety risk 2) Population at risk (PAR) is not the same as potential life loss.To make risk-informed decisions, we need more resolution in our life loss estimates than what can be inferred from hazard classification or PAR. The tools to estimate potential life loss from flooding continue to improve, making these estimates more reliable. These tools also provide a means to scale the effort of estimating life loss to the decisions they inform.This presentation will include data collected by the US Army Corps of Engineers related to their dam and levee portfolios to demonstrate why PAR is not well correlated to life safety risk or life loss consequences. In addition, specific examples will be used to illustrate the differences between PAR, life safety risk, and life loss consequences. Existing and new tools for estimating life loss will be discussed.