“It’s what we stay awake nights trying to make sure we’re ready for,” said Chuck Hamby, a Florida-based spokesman for Verizon Wireless. “How people communicate has changed, and it’s continuing to change. We want to make sure we’re there for our customers.”

When a natural disaster like Katrina (or, on a much smaller scale, last year’s earthquake in Washington, D.C.) occurs, there are at least two destructive dynamics at play. The first, naturally, is equipment damage caused by wind, flooding and debris.

But the other reason a call might not go through or Twitter won’t load can be just as critical: Almost everyone is trying to use the network at the same time. The existing infrastructure can’t handle that much volume all at once.

However, text messages use far less bandwidth — the transmission capacity of an electronic device — and can often get through when calls cannot. That was the case in Haiti after its catastrophic 2010 earthquake, allowing volunteers to communicate, and ultimately saving lives.

As for widespread commercial power loss — which was a bigger problem during Katrina than actual equipment failure — Hamby said Verizon has made improvements in recent years.

Now, most of the provider’s cell sites come with generators and backup batteries that will allow the towers to remain operational without commercial electricity for up to 10 days.

(Of course, that’s irrelevant to the customers whose phones go dead after the first day because they have nowhere to charge them.)

Similar safeguards are in place at AT&T, which says it has invested $600 million in its network disaster recovery program. When the next big storm hits, the company will deploy emergency communications vehicles to provide broadband service, Wi-Fi and voice connectivity for the repair teams as soon as it’s safe to drive.

Furthermore, AT&T has a fleet of mobile towers it will send to places where the network has been damaged, restoring service faster than ever.

“We’re going to come in as quickly as possible, but it could be a day or a couple of days, depending on the severity of the damage,” said Kelly Morrison, a senior network specialist for AT&T. “Having a diverse set of communications devices is critical. If I lived in Florida, I’d own a battery-powered radio and an inventory of batteries to help me cope as well as I could.”

Problem is, there are many who don’t heed Morrison’s advice. Because of South Florida’s transient nature, tens of thousands of people have moved here since the region’s last major storm, Hurricane Wilma, struck late in the 2005 season.

That’s why Miami-Dade’s Office of Emergency Management communicates on several platforms — including television, radio, text message and Internet. Jonathan Lord, OEM’s deputy director, also urges residents to buy a National Weather Service radio, but realizes not everyone will.

“We’re not going to focus on just one tool,” Lord said.