California Coast & Ocean

Tammy Martinez looked around her home set in the sweeping flatlands of the Sacramento-San Joaquin River Delta and felt a buzz of pleasure. It was roomy, tasteful, and best of all, brand new. After the police helicopters and car chases near her family's old home in the city of Pittsburg, 15 miles to the west, she relished the tranquility of the Summer Lake community, which was built in 2006 just east of Oakley, in the watery region at the confluence of California's two biggest rivers, the Sacramento and San Joaquin.

Martinez, 38, would still easily get to her job as a bus driver at Tri Delta Transit in Antioch. Her husband, Roderich, would have a 40-mile commute to Richmond Sanitary District in the East Bay-but that was a small price to pay considering what they now had. She stepped out the back door with her two kids-to gaze at the sky, open fields beyond the houses and, oddly, an awful lot of sand in the ground . . . as though this had once been the bottom of a lake.

The Martinez family is one among thousands who have bought new homes in residential developments constructed on subsided diked lands in the 1,153-square-mile delta where the rivers meet and flow into San Francisco Bay. Many of these homes are on former wetlands, five feet or more below sea level.

Tammy Martinez knew about New Orleans, of course. She had also heard a lot from the Shea Homes sales agents about the strong four-mile levee that was built last year in a circle around the Summer Lake community. She wasn't worried--even though her own home is five feet below sea level.

"We feel safe here," she said. "Everything is inspected. I don't think they would allow you to live in their community if it wasn't safe. We have a sports club and a canoe club. We love it here."

The Martinez's home is on the Hotchkiss Tract, one of 57 manmade islands surrounded by levees that were built a century or so ago to turn tidal marshlands into farmland. Using picks, shovels, and wheelbarrows, farmers, former miners, and Chinese laborers constructed 1,100 miles of levees to protect fields of rich peat soil where they planted corn, asparagus, sugar beets, pears, rice, and other crops. Over the years, the peat soil dried and settled. Levees built at five feet were eventually raised as high as 30 feet as the ground kept sinking. Now the Delta is a maze of deep basins and sunken tracts surrounded by earthen dikes. In NASA satellite photos, it looks like a colorful plate of spaghetti. In places where Delta farmland is 25 feet below sea level the islands are actually holes--some of them deeper than San Francisco Bay.

That the Delta is a disaster waiting to happen has been widely acknowledged for a long time. Since 1900, Delta levees have broken 162 times and flooded more than 250,000 acres. Calls for action became more urgent after Hurricane Katrina tore apart the levees in New Orleans and decimated illusions that the laws of nature and physics could be thwarted by piles of dirt and rock. It was not reassuring that the New Orleans levees were built to a higher standard than most of the aging levees in California's Delta.

More than half a million people reside in the triangular Sacramento-San Joaquin River Delta. Many more are being drawn in by the relatively inexpensive homes being built there, within an hour's drive (assuming reasonable freeway flow) from the major population centers of the San Francisco Bay Area and Sacramento.