More on the subject of levee risk

Gil Cosio didn’t mince words in commenting on the erroneous information that went into the new PPIC report, saying that the PPIC didn’t gather all the data that they should have because of time constraints.  “Garbage in, garbage out,” he said.  “Lund’s data is just not right.”

Last week PPIC author Jay Lund wrote a blog post with “a timeline of published technical and scientific work and events indicating that many Delta levees are at substantial risk, involving independent researchers using diverse methods over several decades.”  The timeline starts in 1931 and includes events in which islands were flooded and abandoned by their owners.

Leaving aside for the moment the decisions of individual landowners to “repurpose” their own property (which is different from having the state take it over), what the timeline tells us is that ongoing (but not insurmountable) engineering challenges are associated with a region like the Delta.  How we address them is an engineering (and a political) rather than a scientific question.

As engineer Dr. Robert Pyke notes, “Evaluation of the risk to the Delta levees requires specialized knowledge of geotechnical and earthquake engineering and the specific conditions in the Delta.”

Says Dr. Pyke, “The only reasonably up-to-date, comprehensive study of the vulnerability of Delta levees is the much-debated Delta Risk Management Strategy. . . .  I believe they were correct in concluding that DRMS developed a good framework for assessing risks to the Delta levees but that one should be wary of taking the results literally. . . . [The] DRMS effort was schedule driven and had data gaps that were drawn to DWR’s attention but never filled. . . .  Further, significant improvements have been made to some Delta levees under the subventions program since DRMS was completed, so that DRMS may already be out-of-date.”

Dr. Pyke notes that additional data continues to be developed by reclamation districts as well as the Corps of Engineers.  “I would suggest,” he has written, “that [the Delta Stewardship Council] should take the lead in drawing on the results of these additional studies and use the DRMS framework to make updated and better estimates of current and future risks to the Delta levees.”

In his blog post, Lund mentioned the January USGS presentation to Delta Stewardship Council concluding “that earlier studies have significantly underestimated seismic risk in the Delta.”  Pyke notes that USGS management subsequently issued a retraction of these remarks.

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