## The Statistics – Flooding threats versus Earthquake Hazard

__Flood Control Versus Earthquake Threat: The Statistical Jumble of It All____ __

__Flow (Flood) Numbers and Estimates__

The Numbers:

- 500 year event: a
**1/500, or 0.002**probability that the American River produce flows of ~520,000 cfs, which is 80% greater than any historically-recorded flow. - 250 year event: a
**1/250, or 0.004**probability that the American River produce flows of ~400,000 cfs, which is 50% greater than any historically-recorded flow.

How The Numbers Were Calculated:

- Corps of Engineers, NRC, and The Bureau of Reclamation all put forth different frequency estimates.
- Corps of Engineers used mathematical computer modelâ€¦ took 100 years of stream flow data and plugged it into the model. Model then generated frequency estimates both for those flows and flows never before recorded.
- Parameters Assigned: NONE!

The Variables That Affect Real Flows:

- Precipitation, current water levels, current snowpack
- Size and existence of Pineapple Express storm
- Global Warming
- Reason to believe these (storm size and global warming effects) should or shouldnâ€™t have a limit on them???

__Earthquake Numbers and Estimates__

The Numbers:

- 2 to 30% chance that filling a reservoir at Auburn would trigger a large quake. This translates to a
**0.02-0.30 probability, or a 1/50**chance. - Need to know the percent chance that this resultant quake is then >6.5, or big enough to create displacement > the Bureauâ€™s estimated 5 inches. (The new gravity dam is based on these numbers.)
- Finally, what is the percent chance, then, of dam failure?
- It may still be bigger than 1/500!!
- USGS warns of a greater degree of uncertainty than the Bureau is basing its estimates upon.

The Variables That Effect Quake Size and Occurrence:

- Water Weight (related to depth of reservoir)
- Fault Activity- Oroville suggests the faults are active
- Draw-down and refilling of reservoirs has been linked to reservoir-induced seismicity.

*THE POINT: AN EARTHQUAKE AS A RESULT OF AUBURN IS MUCH MORE â€œLIKELYâ€ THAN THE FLOODS THE DAM IS SUPPOSED TO PROTECT US FROM!