The president has defended his administration's response to the fatal flooding amid criticism that federal assistance could have been provided more quickly.

Viral posts promoted false claims that cloud seeding, a form of weather modification, played a role in the devastation. Meteorologists explain it doesn't work that way.

A flash flood is a rapid rise of water along a stream or in a low-lying urban area, the National Weather Service said. Flash flooding can result from slow-moving thunderstorms, from numerous thunderstorms that develop repeatedly over the same area, or from heavy rains associated with tropical cyclones.

Hurricane Katrina is the deadliest flood event in the U.S. in the past 25 years. The storm crashed into the Gulf Coast and caused devastating flooding when levees failed in New Orleans, where people had to be rescued by boat and helicopter from rooftops.

KERRVILLE, Texas -- Several hundred people gathered for a worship ceremony at a high school stadium in Texas on Wednesday evening to remember the at least 120 people who died in the catastrophic flash floods over the July Fourth holiday, as well the many still missing.

The deadly flood in Nepal's Bhote Koshi River that killed at least nine people and left more than two dozen missing this week was triggered by the draining of a supraglacial lake in the Tibet region of China,

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.

Fire crews and trained search dogs from the Bay Area have been deployed to Texas to assist in ongoing rescue efforts as catastrophic flooding continues across the state. As of Wednesday, more than 160 people were missing and at least 100 have died, according to the Associated Press.