HOUSTON — Some of the callers are panicking; others exude a strange serenity. One moment, Harvey’s floodwaters are pouring into a home, the next a motorist is trapped on an inundated interstate. A woman goes into labor in a washed-out neighborhood, and a split-second later, a family seeks rescue from their attic. The pleas for help stream in hour after hour, call after call after call.

In the thick of a paralyzing storm and its aftermath, the weight of this swamped city’s problems are landing at the cavernous 911 call center, where operators are racing to keep up as people dial in by the tens of thousands.

“This is like nothing we’ve ever experienced before,” operator Erika Wells says, in a short reprieve between calls.