At least 13 people have died across five parishes in Louisiana after the areas received 6,900,000,000,000 gallons of rain in one week. According to Red Cross: 7,000 people are in shelters, and thousands more are without power.

Livingston Parish, Louisiana (CNN) — The catastrophic flood devastating Louisiana is now the worst natural disaster to strike the United States since Hurricane Sandy four years ago, the Red Cross said.

"Thousands of people in Louisiana have lost everything they own and need our help now," said Brad Kieserman, the Red Cross' vice president of disaster services operations and logistics.

"This disaster is the worst to hit the United States since Superstorm Sandy, and we anticipate it will cost at least $30 million a number which may grow as we learn more about the scope and magnitude of the devastation."

The calamity struck quickly and ferociously. In one part of Livingston Parish, more than 31 inches of rain fell in 15 hours. "I bought enough food to last for a week in case we were flooded in, but I wasn't prepared for this much devastation," said Jo Lee Misner, who lives in the Livingston Parish community of Colyell. "Local stores are running low on everything from food to fuel."
"It's unbelievable what we've been through," she said. "We never imaged this would happen."

And it's not over. At least 13 people have died across five parishes. And with more rain forecast, the destruction could mount.
A road in Baton Rouge was relatively dry Saturday but was inundated by Sunday.

US Homeland Security Secretary Jeh Johnson visited flood-stricken areas Thursday, a day after the director of the Federal Emergency Management Agency arrived.

President Barack Obama had directed FEMA Director Craig Fugate to "utilize all resources available to assist in the response and recovery," the White House said. Obama has declared at least 20 parishes as disaster areas. But the President has been criticized for continuing his vacation at Martha's Vineyard instead of visiting the flood zone and victims. However, the Obama visited the victims today to their surprise and the president himself was surprised by the level of damage done by the floods.

The US Coast Guard, National Guard, local emergency responders and even neighbors have helped rescue more than 30,000 residents and 1,400 pets.
On Thursday, some residents returned to their homes, only to find their belongings soaked and destroyed. Heaps of drenched furniture, mattresses and toys were piled up on lawns as owners struggled to find anything salvageable.

The costliest US floods:

Hurricane Katrina in 2005: $16.3 billion

Superstorm Sandy in 2012: $8.3 billion

Hurricane Ike in 2008: $2.7 billion

Hurricane Ivan in 2004: $1.6 billion

Hurricane Irene in 2011: $1.3 billion

Source: Federal Emergency Management Agency.

Gov. John Bel Edwards said at least 40,000 homes have suffered at least some damage. It's not clear how many are uninhabitable.  He called on volunteers to help clean out mud from homes.

"Not everyone can do this on their own," the governor said. He said anyone interested in helping can visit VolunteerLouisiana.gov. The Red Cross has also asked for donations to help more than 7,000 people in emergency shelters. "Thousands more are without power in hot, humid conditions," the aid group said.