The lowdown on California's levees as another atmospheric river approaches

Once one realizes just how dependent the Bay Area is on levees, we can understand their true importance.

That's because, few things are more damaging and destructive than a levee break and we've covered many of them over the years.

Given the amount of levees in California, almost 9,200 miles of them, really big levee breaks are few and far between.

When a levee breaks, the U.S. Army Corps of Engineers often plays a very big role.

"Most of our levees in our program have their own sponsors and our sponsors are in charge and responsible for the maintenance of the levee system," said John Conway, the U.S. Army Corps of Engineers Bay Area Program Manager for dam and levee safety. Sponsors include irrigation districts, counties, cities, and other kinds of special districts.

In the nine-county Bay Area, there are 858 levee systems operating more than 1,100 miles of levees with an average age of just over a half century.

The major threats to levees are varied and many, including floods, seeping from aging, seeping from burrowing rodents, earthquakes, and now, the very real threat of sea level rise. This has forced both San Francisco International and Oakland International airports to raised the levels of their levees to prevent flooding or wave action.

"Maintenance is a very important key to the successful performance of the levees. The really need to be maintained. Otherwise, they will not perform as they were designed and constructed," said Conway.

Levee operators who ascribe to Army Corps of Engineers standards, can get help from Uncle Sam if things go awry.

"We evaluate them and inspect them almost on a yearly basis, and for the most part, I would say they're in very good shape. They're well maintained. Should there be any damage to the levee system, the Federal Government would come in and assist on the repairs of that damage," said Conway.

Levees not only protect communities and agriculture, they are instrumental in protecting transportation resources.

Levees protect not only highways, but also railroads and much more.

"Here in the Bay area we have over a hundred miles of freeway on levees, and statewide we have thousands of miles of freeway on levees. So, flooding is one of the things we have to regularly deal with when we have roadways on top of levees," said Bart Ney, Caltrans Chief Bay Area spokesman.

And so, while the break in a Monterey-area levee is unusual, it is not completely unexpected. Lessons learned from this weeks Monterey break will prevent similar failures in the future.