Louisiana's mammoth flooding: By the numbers

(CNN)Catastrophic flooding has swallowed swaths of Louisiana in a deluge that the governor calls "unprecedented." But the breadth of the destruction can be hard to imagine.

Here's what the calamity looks like, by the numbers:

60,000: Homes damaged

    Ryan Evans walks along a flooded road on August 15 in Baton Rouge, Louisiana.
    More than 60,000 homes have been reported damaged by Louisiana parishes impacted by the flooding, said Mike Steele, the communications director for the Louisiana Governor's Office of Homeland Security and Emergency Preparedness. However, the damage may be much greater. Steele says a forthcoming assessment by FEMA will be more thorough.
    Health risks of mold

    • After flooding, lingering dampness in walls, wood, carpets and homes provide perfect environment for mold to spread, posing serious health risks.
    • Infants, children, pregnant women, seniors and people with existing respiratory conditions or immune deficiency are at higher risks for getting affected by mold.
    • Inhaling large quantities of mold can cause respiratory problems, congestion, cough and nervous system pains like headaches. Symptoms also include eye, nose, throat and skin irritations.
    • If you're allergic to mold, you may have difficulty breathing or shortness of breath.
    • Recent studies suggest potential link of children getting asthma when they're exposed to mold early on.

    Sources: FEMA and CDC

    Gov. John Bel Edwards said Tuesday that volunteers are needed 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 entire state of Louisiana has just 4.6 million people -- less than the population of metro Atlanta.

    6,900,000,000,000: Gallons of rainfall in one week

    About 6.9 trillion gallons of rain pummeled Louisiana between August 8 and 14, according to meteorologist Ryan Maue.
    That's enough to fill more than 10.4 million Olympic-size swimming pools.

    13: Deaths across the state

    A boat motors between flooded homes after torrential rainfail in Hammond, Louisiana.
    Officials have reported five in East Baton Rouge Parish, three in Tangipahoa Parish, two in St. Helena Parish, two in Livingston Parish, and one in Rapides Parish.

    $30 million: The estimated cost of the flood so far

    "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," Red Cross official Brad Kieserman said.
    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

    31.39: Inches of rain in one day

    Residents grapple with epic flooding in Livingston Parish, Louisiana.
    More than 2 1/2 feet of rain pummeled part of Livingston Parish on Tuesday, the National Oceanic and Atmospheric Administration said.
    The hardest-hit part of the parish was Watson, where 31.39 inches fell between 6 a.m. and 9 p.m. Tuesday.
    Baton Rouge was pounded with more than 19 inches of rain during those same 15 hours.

    20,000: People rescued

    Members of the Coast Guard and National Guard, along with emergency responders and regular civilians, helped take more than 20,000 residents to safety, officials said.
    Gov. Edwards said 1,000 pets have also been rescued.
    Ann Chapman from the Louisiana State Animal Response Team carries a dog she helped rescue in Baton Rouge.

    500 years: Expected frequency of a flood this big

    A man navigates a boat of rescued goats in Gonzales, Louisiana.
    The likelihood of a flood this catastrophic in the Baton Rouge area is about once every 500 years.
    Since last August, five other floods across the country have been considered "500-year floods," according to data from the National Oceanic and Atmospheric Administration.

    14.9 feet: Level of Amite River on Wednesday

    For three consecutive days, the Amite River at Port Vincent broke the previous record level of 14.6 feet. After cresting at 17.45 feet early Monday, the river stood at 14.9 feet Wednesday.

    12: Parishes declared as disaster areas

    Rescuers move cattle across a flooded street to dry land in Sorrento, Louisiana.
    President Barack Obama has granted Edwards' request for an emergency declaration in 12 parishes, the governor said Tuesday.
    Edwards said he expects that number to rise, as he has requested emergency declarations in more than a dozen other parishes as well.

    106,000: Households registered with FEMA

    More than 106,000 individuals and households have registered with FEMA for assistance as survivors are in need of temporary rental help, essential home repairs and other disaster-related needs. More than $55 million has been approved to help survivors.