Updated Aug. 28, 2017, 1:12 p.m. ET

(Bloomberg) -- Hurricane Harvey’s second act across southernTexas is turning into an economic catastrophe — withdamages likely to stretch into tens of billions of dollars and anunusually large share of victims lacking adequate insurance,according to early estimates.

Harvey’s cost could mount to $30 billion when including theimpact of relentless flooding on the laborforce, power grid, transportation and other elements that supportthe region’s energy sector, Chuck Watson, a disaster modeler withEnki Research, said in an email Monday.

Related: Hurricane preparation: Be sure to beinsured

That would place it among the top eight hurricanes to everstrike the U.S. David Havens, an insurance analyst at Imperial Capital, said the final tally might be ashigh as $100 billion.

Less than a third of Harvey’s losses are likely to be insured,Watson said.

Low-income residents

Steve Moore, a 68-year-old who owns Houston’s Villa SerenaCommunities, about 5,000 apartment units that rent for about $500 amonth each, expects more than $10 million of damage. Moore said thebuildings aren’t fully insured.

Many of the low-income residents who live on lower floors of hisbuildings near the Houston airport had some flooding, but nobodywas hurt, he said.

“I’m pretty depressed this morning,” said Moore, who tripped ona curb earlier Monday while surveying the damage and lost his phoneand credit cards in three feet of water. “It’s just a mess.”

'Historic event is currently unfolding'

“A historic event is currently unfolding in Texas,” AonPlc wrote in an alert to clients. “It will take weeks until thefull scope and magnitude of the damage is realized,” and alreadyit’s clear that “an abnormally high portion of economic damagecaused by flooding will not be covered,” the insurance brokersaid.

Many forecasters were hesitant over the weekend to makepreliminary estimates for how much insurers might pay, potentiallyspeeding recovery. Researchers were shifting from examiningHarvey’s landfall Friday as a roof-lifting category 4 hurricane tothe havoc it later created inland as a tropical storm. Typicalinsurance policies cover wind but not flooding, which often provescostlier. Blaming one or the other takes time.

In the Houston area, rainfall already has surpassed that oftropical storm Allison in 2001, which wreaked roughly $12 billionof damage in current dollars. In that case, only about $5 billionwas covered by insurance, according to Aon.

Those storms are dwarfed by Hurricane Katrina, which struck in2005 and devastated New Orleans. By some estimates, it inflicted$160 billion in total economic damage.

Less than 1/6 of Houston's homes have NFIP coverage

Most people with flood insurance buy policies backed by the federalgovernment’s National Flood Insurance Program. As of April, lessthan one-sixth of homes in Houston’s Harris County had federalcoverage, according to Aon. That would leave more than 1 millionhomes unprotected in the county. Coverage rates are similar inneighboring areas. Many cars also will be totaled.

“A lot of these people are going to be in very serious financialsituations,” said Loretta Worters, a spokeswoman for the Insurance Information Institute. “Most peoplewho are living in these areas do not have flood insurance. They may be able to collectsome grants from the government, but there are not a lot, usuallythey’re very limited. There are no-interest to low-interest loans,but you have to pay them back.”

The federal program itself is already struggling with $25billion of debt. The existing program is set to expire on Sept. 30 andis up for review in Congress, which ends its recess Sept.5.

People push a stalled pickup to through a flooded street inHouston, after Tropical Storm Harvey dumped heavy rains Sunday,Aug. 27, 2017. (AP Photo/Charlie Riedel)

Costs likely to soar for insurers & reinsurers

Costs still will likely soar for insurance companies and theirreinsurers, biting into earnings. As Harvey bore down on thecoastline Friday, William Blair & Co., a securities firm thattracks the industry, said the storm could theoretically inflict $25billion of insured losses if it landed as a “large category 3hurricane.”

Policyholder-owned State FarmMutual Automobile Insurance Co. has the largest share in themarket for home coverage in Texas, followed by Allstate Corp., which is publicly traded. WilliamBlair estimated that, in that scenario, Allstate could incur $500million of pretax catastrophe losses, shaving 89 cents off ofearnings per share.

Investors began bracing for losses last week. But many didn’tbelieve that Harvey could wipe out bonds that were issued toprotect insurers against storm damage in the region, according toBrett Houghton, a managing principal at Fermat Capital Management.His firm manages more than $5 billion, with allocations tocatastrophe bonds.

The Swiss Re Cat Bond Price Return Index dropped 0.44% inthe week ended Aug. 25, the steepest decline since January. Thebenchmark is recalculated every Friday, so it’s unclear how thedebt performed as the storm continued through Sunday.

Reinsurers, which provide a backstop for primary carriers, alsomay get burned. That group include Bermuda-based companies ArchCapital Group Ltd., Axis Capital Holdings Ltd. and RenaissanceReHoldings Ltd., according to a note last week from Meyer Shields, ananalyst at Keefe, Bruyette & Woods.

Interrupting business

Businesses are probably better covered than individuals. Companiesacross the retailing, manufacturing, health-care and hospitalityindustries will be seeking reimbursements from insurers for lostrevenue during the storm and subsequent repairs, said Aon’s JillDalton, who helps manage claims.

Related: 3 ways to ease the business interruption claimsprocess

But for Texas’s massive energy industry, it’s still too early toproject how badly the storm will disrupt supply and distribution.That’s because the devastation keeps spreading.

“If it continues to rain, I just don’t think the situation isgoing to get better any time soon,” said Rick Miller, who leadsAon’s U.S. property practice. “In fact, it could get a lotworse.”

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