Roads, refineries and other infrastructure have taken a beating in the Texas and Louisiana regions hit by Harvey -- but cellphone networks so far remain largely functional.
One reason: Big carriers brought in supplemental equipment and backup power and turned to drones to diagnose problems.
Four Gulf Coast counties northeast of Corpus Christi, Texas, had more than half of their cell towers knocked out earlier in the week, but crews have been able to restore many of them. As of Wednesday, Aransas County had the heaviest outages, with 47 percent of its 19 towers out. That's down from 95 percent right after the weekend's storm, according to data from the Federal Communications Commission.
Throughout the affected region, just 4 percent of cell towers were out. It was just slightly higher at 5 percent in Houston's Harris County.
While cellphone services fared well, hundreds of thousands of people lost landline or other wired phone services, according to the FCC. Some 911 centers had to transfer calls to neighboring centers, while three television stations lost broadcast capabilities.
Here's a look at communications in the affected regions.
All told, the devastating storm knocked out fewer than 400 of the 7,804 cell towers in the affected counties; just 329 were down as of Wednesday. By contrast, Hurricane Katrina disabled more than 1,000 cell towers in 2005.
Cell towers typically have backup batteries and generators so they can keep operating in a power outage. The problem comes when generators run out of fuel. Verizon spokeswoman Karen Schulz said crews prepared by topping off all generators ahead of the storm. The company also bought spare fuel and had refueling trucks on standby at key locations.
In a few cases, there's damage to the fiber lines that connect cell towers to communications centers. In such cases, it might be possible to get a signal, but the data isn't going anywhere. Schulz said Verizon has microwave technology to temporarily bridge those gaps.
Verizon and AT&T have both sent out drones to assess damage at cell towers. Crews are still necessary for repairs, but the drone inspections allow companies to determine whether a tower simply needs refueling or requires extensive repair. Cellphone companies also sent truck-based mobile cell towers to areas needing greater capacity.
As of Wednesday, about a dozen 911 centers were out of service, mostly in Texas, but all of them were able to reroute calls to neighboring call centers. In a handful of those cases, the alternative center isn't able to get callers' location information automatically, which is a problem if the caller is unable to speak. Earlier in the week, two centers were down completely, but one has been restored and the other rerouted.
The bigger problem is call volume. Many callers in the Houston area were placed on hold until a dispatcher was free, said Trey Forgety of the nonprofit National Emergency Number Association. In a few cases, callers got busy signals.
"We're part of the telephone era, so if you want to move calls around (to neighboring centers), you have to go physically rewire things," he said.
The FCC said that at the peak of the outage, at least 283,000 households lost wired phone services -- both traditional landlines and internet phones such as cable. That decreased to about 267,000 by Wednesday. In comparison, Katrina knocked out more than 3 million phone lines.
People are far less dependent on wired phone services these days. U.S. households with only cellphone service hit a majority for the first time in the second half of 2016, according to a government survey.
The FCC said three Texas television stations -- KUQI in Corpus Christi and KFDM and KBTV in Beaumont -- were out of service. However, the outages appeared to affect only over-the-air broadcasts. KUQI was still viewable on cable as of Wednesday afternoon. KFDM and KBTV streamed their channels online.
Several radio stations also lost service -- five as of Wednesday, all in Texas.
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