Yuba River Basin GRR F4 hydraulics appendix

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These analyses were done with the intent that the results will be used to perform an economic evaluation of plans for the purpose of identifying the NED plan. The without-project alternative was previously defined and documented in the F3 hydraulics appendix. There, without-project hydrology, hydraulics, and risk parameters were established as a starting point for the analyses described in the F4 hydraulics appendix. In the F4 hydraulics appendix, 3 additional alternatives are evaluated. Each of these 3 alternatives consists of levee improvements and levee alignments. Alternatives 1 through 3 were each defined for 4 design levels, which were in turn defined by water surface profiles for 100-year, 150-year, 200-year, and 200-year plus 2 feet. </div> <bR> </tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=3 BGCOLOR=#339933 HEIGHT= 16 WIDTH="537"><div> <B>Action</B></div> </tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=3 HEIGHT= 557 WIDTH="537"><div> Hydraulic models were used to (1) define design water surface profiles for evaluation of design improvements to existing levees and design of setback levees, and (2) provide frequency-discharge-stage information required for evaluation of project performance at index locations. The HEC-RAS models from the F3 phase of the Yuba River Basin Study, which were used to establish without-project water surface elevations, were modified to represent the 3 project alternatives. 10 exceedence probability events were modeled. 4 index points were used for economic evaluation of plans, and two index points were used to evaluate downstream hydraulic impacts.<IMG SRC="23a9c3d0.jpg" border=0 width="412" height="317" ALIGN="RIGHT" HSPACE="8" VSPACE="10"></div> <div> A risk analysis was conducted following the guidelines of Corps of Engineers engineering manuals 1110-2-1419 and 1110-2-1619. The software program HEC-FDA was used to evaluate engineering performance at 7 index locations.</div> <div> Results of the hydraulic and risk analyses were presented to the Corps for economic evaluation of alternatives.</div> <bR> <bR> </tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=3 HEIGHT= 223 WIDTH="537"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="223" ALIGN="bottom" WIDTH="537" HSPACE="0" VSPACE="0"></tD> </tR> </TABLE></div> <bR> <bR> <bR> <bR> </td> </tr></table></body>