Orestimba Creek Feasibility Study - Stanislaus County

Economics Appendix – Draft Report - Orestimba Creek Feasibility Study, Stanislaus County, California – September 2012
6.0 With Project Conditions –Flood Damage Reduction Benefits
Project Benefits – The Role of Economics in the Plan Formulation Process
This section will describe how benefits of flood damage reduction of various potential
alternatives were estimated. In this section, benefits and project performance outputs will be
limited to flood damage reduction components. Non-monetary outputs such as environmental
measures, which may vary for the final array of alternatives, are not included but may factor in
the plan formulation decision process.
6.1 2009 Preliminary Incremental Alternatives Analysis
An economic analysis was performed in 2009 which served as a screening to get to the final
array of alternatives. After 2009, the Hydraulic and Economic models were updated and re-run
for the final array. The results provided in this section summarize the screening results from the
old models and therefore, the without project condition damages will not be the same as those
provided in section 5.0 of this report. The 2009 analysis has not been updated for price level, so
it remains in October 2008 prices and interest rates.
On Orestimba Creek, flood damage reduction measures have been considered and screened
during several phases of the study. In Table 6-1 below, you’ll find a matrix of most of the
different measures that have been evaluated throughout the screening process and variations of
the alternatives that have been screened. In this section of the economic appendix, flood damage
reduction benefits have been explicitly calculated for the measures that might be feasible and
have been carried forward in the plan formulation.
Benefits were calculated on incremental basis, and these increments are described in more detail
in the main report. In summary, there were 3 different categories of increments being considered
for Orestimba. First were the pieces of the project which included a chevron levee, channel
modification, interceptor channel, or some combination therein. Second was the location of
chevron levee to be placed either north along the CCID Canal, then east along Stuhr Rd; or
further north along the CCID Canal and then east along Lundy Rd. The third increment category
was the design level of the project/levee to the mean WSEL of a specific event (i.e. 1%, 0.5%,
0.2% annual chance event design).
The goal of this incremental benefit analysis is to answer three simple questions: what, where
and how big should the project be Is there a federal interest to construct a continuous project
providing flood damage reduction to all impact areas And what could be the optimal size of
project for these areas
For a more detailed description of these preliminary alternatives and other conceptual
alternatives, please refer to the plan formulation portion of the main report.
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