Bruce Maiman: Building again in Natomas is too risky

Growth is returning to Natomas, but a troubling question is going to be ignored or dismissed by those with the power to address it: Is building in a floodplain a good idea?

The rapid development in Natomas came to a screeching halt in 2008 when federal authorities revoked the area’s 100-year flood protection rating. But the newly enacted Water Resources Reform and Development Act authorizes the Army Corps of Engineers to finish fortifying the 42 miles of levees encircling the Natomas basin, much to the excitement of developers, realtors and Sacramento City Hall – all of whom are ready to cash in on new neighborhoods, strip malls, sales commissions and property taxes.

This is misguided enthusiasm, said Ian Adams, a policy analyst specializing in insurance markets for R Street Institute, a libertarian think tank. “Overhauling the levees makes sense for existing residents, but not as a basis for further development.”

“It depends on what precautions have been taken to secure that floodplain,” countered Angelique Ashby, the Sacramento City Council member who represents Natomas with unbridled passion. “Natomas, particularly North Natomas, was specifically engineered to withstand a major weather event.”

“Last year’s heavy rain was a real test of the system,” Ashby added, referring to a five-day stretch last December that delivered nearly 5 inches of rain to the region. “Will that engineering beat Mother Nature on the day we need it to? All indications so far show we’re doing quite well.”

So far.

There is no dispute: After New Orleans, Sacramento – which sits at the confluence of the Sacramento and American rivers and near the Delta – is the nation’s most flood-prone city. Natomas, with its 100,000 residents and $7 billion worth of property, is particularly vulnerable.

Two events could destroy the levees and cause a mega-flood. One is an earthquake. Seismologists say a quake of 6.7 magnitude or greater in the vicinity of the Delta has a 62 percent chance of occurring sometime before 2032.

The more likely threat is a violent Pacific superstorm, the so-called Pineapple Express, dumping ocean water with fire-hose intensity. Using a composite of three historical storms to estimate a worst-case event, the U.S. Geological Survey developed a winter storm scenario – aptly named “ARKstorm” – that would overwhelm many of the state’s 1,100 miles of levees, with much of Natomas likely submerged under 20 feet of water.

Federal flood insurance data is illuminating. Over the life of a 30-year mortgage, homes in Natomas have a 26 percent chance of flooding. In the free market, insuring a $300,000 home in Natomas with $280,000 in coverage would cost about $21,000 annually. The cost under the federal government’s National Flood Insurance Program is $353 annually – what Adams calls “a massive transfer of risk from a small percentage of homeowners onto the backs of all U.S. taxpayers.”

But there’s more.

A new building boom would substantially increase potential flood losses, currently estimated at $8.6 billion, and that’s just for Natomas homeowners and businesses and doesn’t count the impact on Sacramento International Airport, 32 schools and nearly 100 million motorists annually traversing the intersection of interstates 5 and 80.

“Ironically, even though we’re reducing the probability of risk through levee improvements, as Natomas develops more that risk will be higher, maybe even more than before we started levee improvements,” Army Corps spokesman Chris Gray-Garcia said.

Nor do 100-year floods happen once a century; that designation means they have a 1 percent chance of happening every year. Devastating floods have occurred along the Mississippi River in 1993, 2008, 2011 and now. We’re seeing a second straight year of flooding in Colorado. Flooding has occurred in Sacramento in 1986, 1997 and 2006. Since 1950, the American River has set five flood records, meaning floods have been getting more severe for 60 years. Experts predict climate change will bring more frequent and increasingly intense winter storms.

“We are staunch believers that you can never eliminate risk; you can only reduce it,” said DeDe Cordell, the Army Corps public affairs chief in Sacramento. “No matter how big, strong or tough we build those levees, Mother Nature can always provide a storm that is bigger and stronger than we prepared for.”

So it’s more than just building in a floodplain. It’s whether we’re wise to incur greater risk and indemnify still more people by funding new development in flood-prone areas when we are virtually assured there will be another calamity.

That discussion won’t happen. Instead, you’ll hear that we shouldn’t use such scenarios to prohibit growth. We’re Californians, they’ll say. We can meet the challenge!

But I guarantee you: They’ll all be people who stand to profit from a new building boom.