Another sobering reminder of the work we have to have done to reach even the minimal protection level of the pre-Katrina levees.
Government August 13, 2007, 12:01AM EST text size: TT
California's Flood-Control Challenge
For reinforcement of vulnerable levees, the governor has won approval for billions in public financing. Will it be enough to avert an infrastructure breakdown?
by Michael Arndt
Since the I-35W bridge collapsed into the Mississippi River on Aug. 1, killing at least five people, politicians at every level of government have refocused attention on how to adequately maintain the infrastructure that supports the nation's $13 trillion economy. While inspectors fanned out to reexamine 750 bridges of similar design, the Senate passed a long-stalled bill the next evening creating a commission to assess the condition of the nation's infrastructure to judge which portions needed the promptest repairs.
But elected officials, like their constituents, have short attention spans. People generally rail against paying higher taxes, too, especially on outlays that are no longer headline news, or have no immediate or direct impact on their own well-being.
In California, however, the long-term commonweal seems to be winning out as authorities race to avert an infrastructure breakdown that might be more calamitous than hurricane-ruined New Orleans: overflowing rivers that could, at virtually any moment, imperil as many as 500,000 people, the nation's richest cropland, and the water source of the majority of the state…
Fertile, Troubled Land
Though levees are almost singularly associated with the Mississippi River, California has more than 2,600 miles of berms embanking rivers and sloughs that fan out from the San Pablo Bay northeast of San Francisco up to Sacramento and Stockton. Before the California Gold Rush, much of this so-called delta was marshland. But as settlers discovered how rich this peaty soil was, they walled off more and more acreage to protect it from spring floods and turned it into farmland, and then communities.
Today this reclaimed land, bigger than the state of Rhode Island, is the most productive farmland in the world, filling grocery aisles with more than $32 billion of vegetables, milk, and meat a year. It is also home to some 2 million people, more than the population of greater New Orleans before Hurricane Katrina hit in 2005. And its mountain-fed rivers provide drinking water for an estimated 23 million people, or 2 of every 3 in California, thanks to aqueducts that stretch from the delta to the outskirts of metro Los Angeles 350 miles away.
Problem is, much of this landscape is in danger. Many of its levees are simply mounds of river muck, piled originally by shovel and wheelbarrow in the 1800s and never designed for long-term protection of homes and other structures. Moreover, the drained land has subsided, leaving huge tracts 15 or 20 feet below sea level.
When the Levee Breaks
Over the last century, California's levees have failed on average once every 7.5 months. Sometimes the breaks are foreseeable, coming, for instance, after a record spring rainfall. Other times, they just seem to happen. In 2004, there was a "sunny day" breach, when a levee gave way without warning on a delta island called Jones Tract; water from the surrounding estuaries quickly inundated 12,000 acres.
These islands—dozens of earth-walled plats separated by narrow channels—remain mostly farmland today. But increasingly they are becoming new communities for people priced out of San Francisco and San Jose 75 to 90 minutes away. Less than 10 miles downstream from Jones Tract, developers are plotting 500 homes on Bethel Island.
Builders in Sacramento are putting houses in flood plains, too. While state and federal authorities say Sacramento's levees are inferior to the pre-Katrina revetments in New Orleans, an estimated 100,000 people now live on what may have been a dry lake bed called the Natomas plain. So far, these homes, with values of $350,000 and up, have been protected. But someone who stays put through his 30-year mortgage would face a 26% chance of a 100-year flood. If the levees broke, waters would deepen to 25 feet, enough to dunk even two-story residences.
Altogether, an estimated 500,000 people now are in danger of flooding in the Sacramento and San Joaquin River basin. A 200-year flood would cause $35 billion in damages to greater Sacramento, the state forecasts, and it would take at least 2.5 months just to pump out flooded areas.
