Here is an article from California Policy Review that looks at the history of the Delta levees and, reminds us of the slowly disappearing quality of the peat upon which they are built.
Here is an excerpt.
What if the levees can’t be repaired?
The New Orleans flood focused attention on California’s dangerously neglected levees. But daunting obstacles will make any ‘fix’ difficult.
by Geoffrey Vanden Heuvel
Posted: March 8, 2006
Nearly two-thirds of Californians and millions of acres of California farmland depend to one degree or another on a water supply that must pass through the Sacramento-San Joaquin River Delta. Historically, the Delta was a tidal marsh located where the Sacramento River from the North and the San Joaquin River from the South converged on their way out to San Francisco Bay. In the late 19th century, farmers began to create islands on this marshland by constructing berms and draining the brackish water off the land into the channels created by the berms. They then began to farm the rich peat soil, irrigating the land using the fresh water from the rivers flowing through the channels they had created.
Peat soil, when it is exposed to the air, oxidizes and disappears. So islands that started out a hundred years ago at sea level, are now holes in excess of 25 feet below sea level. What began last century as modest earthen berms are now large earthen levees that must hold back enormous amounts of water, which is flowing some 30 feet or more above the surface of the land. The Delta levees exceed 1,100 miles in length, with almost all of them resting on unstable peat soil.
Two great water projects
The Delta is the hub of the two great water projects that supply Central and Southern California. The Central Valley Project, with water originating at Lake Shasta, and the State Water Project, with water originating at Lake Orville, both use the Sacramento River to convey water south. When it enters the Delta, the Sacramento River is on its way to the ocean through San Francisco Bay. Some of this water is diverted from the river and sent to thread its way through the Delta to pumping plants located near the town of Tracy. These plants move the water into the California Aqueduct for delivery to Central and Southern California.
The engineers who designed these water projects decades ago knew the vulnerability of the Delta levees. So the original design plans included the construction of a 40-mile canal around the Delta in stable soil to insure that, in the event of a major failure in the Delta, water could still be delivered. But, as we all know, that “peripheral canal” was never built. It was not built right away, decades ago, because the cost to construct the Shasta and Orville Dams and the 400-mile- long California Aqueduct, together with all the water works associated with this huge effort, consumed most of the project’s available funds. The plan was to use the delta channels on a temporary, interim basis to convey the water until additional funding allowed the permanent canal to be built.
In 1982, the Legislature finally authorized the building of the peripheral canal. But then a variety of disparate interest groups banded together to referenda and kill the peripheral canal bill. They succeeded. The canal’s opponents held different reasons for their position. One group disliked a ban on diverting the Eel River into the State Water Project that the Legislature added in authorizing the peripheral canal. (The Eel River was later put on the federal Wild and Scenic River list, which prohibits its being dammed).
