Can the HMCE tool be used to estimate cost effectiveness for a scenario where a 100-year event causes more damage than a 200-year event?
The HMCE tool is designed to accurately interpolate between two or more events with increasing total damages and increasing recurrence intervals (RIs). So for a scenario where a 100-year event causes more damage than a 200-year event; the HMCE tool would not accurately interpolate between the events and would underestimate the actual project benefits. Therefore, to produce accurate results in the HMCE tool, we recommend the following:
If there are only the two known RI events, then input only the 100-year event as a known RI event and omit the 200-year RI event to avoid an undercounting of project benefits and explain your reasoning in the documentation.
If there are three more events including the two known RI events, then input all the events as unknown RI events and let the tool estimate the RIs and group the results.