Listen to Alan... he does this stuff for a living, kinda.
Having personally been involved in the Comm side of how First Responders and others will communicate when they first show up, I can tell ya that in the real-world... nothing really works better than live bodies telling disaster victims exactly where to go and what to do. A sweep of the area if possible.
When the disaster is huge, this is very hard to do and eats up a lot of resources.
Shock is a serious problem in big disasters. If the disaster is predictable (widespread flooding headed your way, lava flows, etc...) the "broadcast" tools, sirens, etc... all help if they're used soon enough and people HEED the warnings.
In areas regularly hit by severe weather, tornadoes, etc... sirens are effective, but there is a tendency for folks to try to "ride it out" for whatever reasons... RE: Katrina.
But for the unexpected, many people are "walking wounded", and have no physical wounds... they're just wandering around lost. You have to have crews dedicated to reaching them and showing them the way to safety.
If you're really getting into Emergency Management, I recommend you take a few FEMA ICS courses online and try to find a friendly larger neighboring jurisdiction to try out a CERT course too. ICS courses are free until you get to the more advanced ones that are done in-person.
Maybe you can spearhead a "train the trainer" type thing with interested area citizens to get CERT going, and get the county/local authorities up to speed on ICS and Mutual Aid requests. CERT's goal is to try to make Citizens NOT walk around in shock, but to self-organize and get neighborhoods ready to weather the disaster or evacuate, etc. It's a pretty good concept on paper. Whether it'll work in reality, remains to be seen.
Small counties and rural areas quite often have to "bring in the troops" (sometimes literally -- National Guard, other times figuratively, by reaching out for Mutual Aid from larger populated areas). Knowing how to "speak their language" via ICS is good. Having built solid relationships with them and doing drills, even better.
How far down the rabbit hole do you want to go?