There's an entire field of study called risk management which takes into account the severity of the event(s), the mathematical probability of the event(s), and the countermeasures needed to make the system (building, aircraft, car, water/sewer infrastructure, cell phone, etc) robust enough to survive it. The FAA has it nicely explained in their Risk Management Handbook (FAA-H-8083-2), chapter 4.

https://www.faa.gov/regulations_policies...ia/rmh_ch04.pdf

For a particular location, check with the local Emergency Management Agency for what they consider the top priorities. The very nature of their work requires heavy risk analysis and management.