Over just two hours, the Guadalupe River at Comfort, Texas, rose from hip-height to three stories tall, sending water weighing as much as the Empire State building downstream roughly every minute it remained at its crest. The force of floodwater is often more powerful and surprising than people imagine.

Here's what to know about the deadly flooding, the colossal weather system that drove it and ongoing efforts to identify victims.

At least 120 people are dead and 173 are missing in central Texas after the Guadalupe River swelled early Friday, causing destructive flash flooding throughout Kerr County.Now, new before-and-after satellite images of several sites throughout Kerry County show the devastation caused by the floods as crews embark on a seventh day of search and rescue efforts.

As the Guadalupe River swelled from a wall of water heading downstream, sirens blared over the tiny river community of Comfort — a last-ditch warning to get out for those who had missed cellphone alerts and firefighters going street-to-street telling people to get out.

In what experts call "Flash Flood Alley," the terrain reacts quickly to rainfall steep slopes, rocky ground, and narrow riverbeds leave little time for warning.

KERRVILLE, Texas (AP) — Over the last decade, an array of Texas state and local agencies missed opportunities to fund a flood warning system intended to avert a disaster like the one that killed dozens of young campers and scores of others in Kerr County on the Fourth of July.

With more than 170 still missing, communities must reconcile how to pick up the pieces around a waterway that remains both a wellspring and a looming menace.

Follow for live updates in the Texas flooding as the death toll rises to 120, as rescue operations start to shift to recovery phase