Report on recent Sacramento conference.
Getting a Grip On California Levee Risk
Sacramento conference is swarmed by experts and policy-makers working to head off disaster
8/1/2007
By Tom Sawyer in Sacramento
Californians are waking up to disaster. Or at least they are waking up to the prospect of a flood and water-supply disaster awaiting them the day key Central Valley levees let go, overwhelmed by roaring rivers, earthquake or, most insidious of all, undetected internal flaws. Hurricane Katrina’s devastation of New Orleans was the wake-up call, water management officials said at a conference on levees in Sacramento, Calif., in late July. They say they now are determined to try to prevent a catastrophe there.
If they succeed they will break with history, claim Dutch flood-control experts. “In Dutch there is a saying, No policy without a calamity,” cautions Sybe Schaap, a Dutch senator and president of the Dutch Association of Water Boards.
The parallels between the Netherlands and California’s Central Valley are many. Vast expanses of land in each case were reclaimed from inland seas by generations of flood-control engineering. Levees in both lands now shelter large and growing populations and incredibly productive agricultural areas, which in many places lie well below sea level.
Schaap says the Dutch got their own wake-up call in 1953 after flood defenses crumbled in their delta lowlands, inundating 700 square miles of farmland and killing 1,835 people. That prompted officials there to launch a plan to strengthen levees, consolidate the 2,600 water boards that had built and managed the flood-control system over 800 years into 26 regional bodies, and refer land-use issues that increase flood risk to a national ministry. It took 50 years to complete the original scope, Schaap says. The work continues to expand.
Like pre-1953 Holland, California’s water management is thoroughly balkanized under the local authority of more than 2,800 water purveyors, more than 200 reclamation districts and “a lot of flood-control districts,” says Michael Miller, a spokesman for the state’s Dept. of Water Resources. Land-use control is local as well, encouraging a rapidly expanding population to move into new, levee-shielded enclaves shouldered by fast-moving rivers.
…Les Harder, deputy director of the Calif. Dept. of Water Resources, noted that risk is rising with climate change, which contributes to wild fluctuations in flood volume. In the upper part of the system the Sacramento and American rivers flow between levees built right on their banks to scour gold mine tailings washing from upstream and keep navigation channels clear. “They confined the river to make it scour, and it was very successful,” says Harder. “Only the mines are gone now, and the river still wants to scour. It’s poorly built out of poor materials, and it has some design flaws.”
During spring floods in 2006, rated as a “five-to-10-year event,” hundreds of spots were damaged and the state declared its first levee emergency, Harder says. The 24 critical sites identified during that season’s flood grew to 104 by the time waters ebbed. The last of $300 million in repairs is to finish this month.
Harder says the state needs to confront the levee problem in part because courts have found it liable for damages when known defects are allowed to persist. “The state did not design the levee system and doesn’t control land-use planning, but it’s still left holding the bag,” he says. But nothing comes easily. One conundrum developed when the Corps said last spring that all woody vegetation larger than 2 in. in diameter would have to be cut from the levees to protect them from piping along root paths or scour if toppled trees ripped out root-balls.
