As the name says, AREDN is a data network built by amateur radio operators for emergency use. What kinds of emergencies do we have in mind? Opinions vary across the AREDN world based on local situations. Here in the City of Palo Alto, we have a range of emergencies, but only a small number that should be the basis for building our AREDN network. Possible scenarios range from the low end in which lifeline services (power, water, communications) are not disrupted to the high end such as earthquakes that we can expect will severely impair lifeline services. We observe that the City has excellent communications resources, and we don't see the need to shore these up for the purpose of supporting relief efforts for small incidents. The City is well-prepared to support themselves, and volunteer workers, while beneficial, won't make the difference between a decent outcome and a tragic one.
Big incidents are the ones for which we must design and train. In big incidents, City resources will be exhausted. Emergency services volunteeers, their supplemental resources, and their training for responding in a large incident will make a substantial difference in the outcome. Training is crucial. And with a volunteer force, it is important to pick the most lilkely scenarios and train for response under those circumstances.
The US Geological Survey has studied past earthquakes to understand how failures lead to failures in a cascade (e.g., loss of power leads to loss of communications) as well as the plate tectonics of our region including the well-known San Andreas fault and the only slightly-less-well-known Hayward fault. By their account, Hayward is on the verge of becoming much more well-known when its energy is released. They have released a study called "Haywired" (here) that considers, among other things, the likely impact to lifeline services. This ground-breaking (pun intended) work helps us understand where we can focus our emergency communications efforts. Together with past papers and research studies (The Silicon Valley Resilient Network, The Survivable Social Network), we are led to design our network to focus on keeping local communication functioning, even when power is out, the cellular networks are down, and internet fiber connections out of the Bay area are impaired or cut. Highways will be impassable for days or weeks, and support from outside the impacted area will be limited. As such, we should focus on local solutions to local needs.
Other types of disasters such as major storms or fires are not unlike earthquakes in the way that they can impact lifeline systems. Preparing for earthquakes will put us in a good position to deal with a variety of lifeline-impacting disasters.