Infrastructure design and construction management firm HNTB, based in Los Angeles, has done a survey asserting that the Delta has 1600 miles of levees, and that 162 levees have failed in their history due to intense rains.
Notes engineer Robert Pyke, “The HNTB fact sheet and press release are inconsistent with the recent findings of the Delta Economic Sustainability Plan. The chapter in the ESP on Flood, Earthquake and Sea-Level Rise Risk Management was researched and written by myself and Mike Conrad, former commander of the Sacramento District of the Corps of Engineers, with significant input from DWR and the local reclamation district engineers. We found that at most there are 1,000 miles of levees in the legal Delta and that there are about 650 miles of the most critical levees that protect land below sea-level in the Primary Zone.
“We found, contrary to many reports in the press and elsewhere, that the Delta levees are not in such bad shape but we recommend that the current program of improvements be completed as quickly as possible and that further improvements be made to address longer-term threats from floods, earthquakes and sea-level rise.”
Regarding levee failures, Pyke says, “The suggestion in the HNTB fact sheet and press release that some Delta levees have failed 162 times must be a mistake in editing. By some counts there have been that many total levee failures, but even that is grossly misleading. As a result of improvements that have been made to the levees in the last 30 years, the rate of levee failures has dropped dramatically, and it is totally misleading to quote historic data on levee failures.”
After all, the history of levees in the Delta goes back over 150 years.