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.

In Kerr County, the hardest-hit region, officials said the number of missing remained unchanged, at 161, since Tuesday. The floods have killed at least 121 people statewide.