The primary argument in favor of building the Auburn Dam is that it will provide â€œ500 year flood protectionâ€ for the Sacramento area. Proponents also claim it would relieve pressure on downstream levees.
Levee repairs and Folsom Modifications are needed firstâ€¦NO MATTER WHAT:
The Problem with that argument is this: Regardless of how many dams there are upstream releasing water into the levees during a flood, they still need to be able to handle the large amounts of controlled releases that could currently destoy them. Also, even if Auburn is upstream letting out water gradually into Folsom, Folsom will need to be able to let water out faster than its current capacity for doing so if Auburn is to have any helpful affect whatsoever.
Bottom line? Levee repairs and Folsom Modifications are needed firstâ€¦NO MATTER WHAT. So why spend money on more studies and deliberations, when there is a solid, clear need that keeps getting ignored? Lets fix the immediate, obvious problem first. THEN we can decide what added protection is desired.
500 Year Flood Numbers Are Not Realistic!
As for that later decision about added flood control, and 500 year protection, there are several different ways of analyzing and projecting flood risks. The 500 year number refers to a modeled probability based upon statistical extrapolation.
Translation? The flow level associated with a 500 year event is a flow level that has never been seen in recorded history, but that in one particular mathematical model has a projected 1 in 500 chance of occuring in any given year.
The most important thing to know about this modeled probability is that the Army Corps of Engineers themselves, (the government agency responsible for creating the statistical model), admitted in their report that the model was NOT MEANT TO EXTRAPOLATE, WITH ANY ACCURACY, FLOW FREQUENCIES BEYOND THOSE WITH A 1 in 200 CHANCE OF OCCURING.
Why? Because the mathematics break down beyond an interval that is more than twice the length of the available data set. And the available data set happens to only be 100 years long.
An Alternative Approach to Estimating Flood Risk:
So, perhaps the Corpsâ€™ frequency model isnâ€™t the best way to try and predict the maximum flood that can be reasonbly expected from the American River Watershed. (They even say so themselves!)
An alternative is to use what is referred to as the Galloway method, in which public projects are built based upon what is called the â€œstandard project flood.â€
Had this analytical method been applied in New Orleans, their system of flood protection wouldnâ€™t have come near standard project flood requirements, and planners may have then had the chance to avert disaster.
Why? Because in determing the standard project flood, analysts take the local weather system and data into account, placing the worst possible storm directly above the watershed and determining what the resultant runoff would look like. New Orleanâ€™s levee and dam system was not built to withstand a Class 4 or 5 Hurricane, even though those storms appear in the Gulf every few years!
In contrast, Northern California only has one, very consistent storm to worry about: the â€œPineapple Express.â€ Unlike the hurricanes the rack the Gulf every few years, it is an extremely predictable storm that we have years and years of historical data on, and it is the ONLY storm that could possibly hit California and cause the floods that we worry about.
There is no good reason to believe that the Pineapple Express will dump 80% more rain into the American River than ever recorded, which is the amount that would be needed to cause a supposed “500″ year event.Â Even with global warming concerns, many experts believe that the Pineapple Express will become more frequent, not bigger.
The Fiscally Responsible Citizen Would Focus on Folsom and Levee Modifications, Rather Than on an Unnecessary, Costly Dam:
Auburn Dam would have several negative affects on top of drowning two incredibly valuable and beautiful river canyons. One, it would cost an incredibly large amount of money to build. Two, geologists at the USGS believe there is a lot of unresolved uncertainty surrounding the very dangerous possibility that the damâ€™s location along a fault system could trigger a devastating earthquake. Three, its water would be too limited and expensive to have hopes of paying off the dam any time in the near future.
With environmental and economic losses so big, is it really worth building a structure based upon a projected risk that is an unreliable estimate at best? Perhaps we should look instead to the numbers that can be trusted:
Sacramento is NOT currently protected against a 200 year event, and can be with repairs to levees and Folsom Dam. Bottom line? Levee repairs and Folsom Modifications are needed first. Why spend money on more studies and deliberations, when there is a solid, clear need for levee improvements and modifications to Folsom dam?