Hydraulic impact analysis

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" rowspan="2" width=185 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> <A HREF="index.htm" TARGET="_top" TITLE="David Ford Consulting Engineers"><U><B><IMG SRC="0d058960.png" border=0 width="88" height="150" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></U></A></div> <bR> <div>    <FONT SIZE="1" COLOR="#000000" FACE="Verdana" > </FONT></div> <div> <B> <TABLE BORDER="0" CELLPADDING="4" CELLSPACING="1" WIDTH="156" BORDERCOLORLIGHT="#FFFFFF" BORDERCOLORDARK="#FFFFFF" FRAME="VOID" RULES="NONE" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP HEIGHT= 27 WIDTH="146"><div> David Ford Consulting Engineers, Inc.</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 27 ><NOBR><div> 2015 J Street, Suite 200</div> <div> Sacramento, CA 95811</div> </NOBR></tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 27 WIDTH="146"><div> tel: 916.447.8779</div> <div> fax: 916.447.8780</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 27 WIDTH="146"><div> <A HREF="mailto:support@ford-consulting.com" TARGET="_top" TITLE="mailto:support@ford-consulting.com"><U>support@ford-consulting.com</U></A></div> </tD> </tR> </TABLE></B></div> <div>    </div> <bR> <div> <A HREF="index.htm" TARGET="_top" TITLE="David Ford Consulting Engineers"><U>Home</U></A></div> <div> <A HREF="id461.htm" TARGET="_top" TITLE="About us"><U>About us</U></A></div> <div> <A HREF="news.htm" TARGET="_top" TITLE="News"><U>News</U></A></div> <div> <A HREF="hydrologic_engineering.htm" TARGET="_top" TITLE="Hydrologic engineering"><U>Hydrologic engineering</U></A></div> <div> <A HREF="water_resource_planning.htm" TARGET="_top" TITLE="Water resource planning"><U>Water resource planning</U></A></div> <div> <A HREF="flood_economic_and_risk_analyses.htm" TARGET="_top" TITLE="Flood economic and risk analyses"><U>Flood economic/risk analyses</U></A></div> <div> <A HREF="flood_warning.htm" TARGET="_top" TITLE="Flood warning"><U>Flood warning</U></A></div> <div> <A HREF="decision_support_system_development.htm" TARGET="_top" TITLE="Decision support system development"><U>Decision support systems</U></A></div> <bR> </td> <td valign="top" colspan=2 height=40 BGCOLOR="#3366CC" TEXT="#080000" bgproperties="fixed" background="14400980ezthpx.png"> <div> <B>Hydraulic impact analysis</B></div> <div> </div> </td> </tr><tr> <td valign="top" height=440 colspan=2 BGCOLOR="#FFFFFF" TEXT="#080000" bgproperties="fixed" background="06c00962egerdp.png"> <div> <TABLE BORDER="0" CELLPADDING="2" CELLSPACING="1" WIDTH="547" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP COLSPAN=3 BGCOLOR=#CC0000 HEIGHT= 16 WIDTH="537"><div> <B>Situation</B></div> </tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=3 HEIGHT= 295 WIDTH="537"><div> Yuba County has a long history of flooding, and floods in the California Central Valley in 1986 and 1997 were especially catastrophic, inundating tens of thousands of acres and destroying thousands of homes and businesses. Major flood protection efforts resulted, one of which has led to a US Army Corps of Engineers project designed to achieve a 200-year level of protection for Reclamation District (RD) 784 within Yuba County. RD 784 is particularly vulnerable to flooding as watercourses, including the Yuba River to the north, Feather River to the west, Bear River to the south, and Interceptor Canal to the east, surround it. The figure below shows RD 784 located in the center.    </div> <div> We were asked by the Yuba County Water Agency to perform a hydraulic impact analysis of designs aimed at reducing the flood risk to RD 784. This analysis included a quantification of the without-project flood risks and 3 alternative designs featuring upstream reservoir modifications as well as levee setbacks, raises, and strengthening options. Results of this analysis would be used to evaluate and select the project alternative that provides the most desirable reduction of flooding risk to the study area.    </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= 302 WIDTH="537"><div> Following current US Army Corps of Engineers procedures, we computed annual exceedence probability (AEP) and conditional non-exceedence probabilities (CNP) for the study area. These values were computed using software developed by the Hydrologic Engineering Center (HEC), HEC-FDA. The Corps' procedures integrate hydrologic, hydraulic, and geotechnical information to compute these statistics. The procedures also account for the impact of uncertainty in this information, using probability distributions for required inputs rather than single average values. This analysis relied on hydrologic, hydraulic, and geotechnical models and an estimate of uncertainty of those models developed by other members of the study team.</div> <div> The focus of this study is the RD 784 area, however the proposed alternatives also affect the water surface elevation at locations in the surrounding area. Therefore, our hydraulic impact analysis included an evaluation of the AEP and CNP at locations in the surrounding area. The study area used in this analysis is shown in the figure below.</div> <div> Computer models, along with a detailed report describing the hydraulic impact results and methodologies, were provided.</div> <bR> </tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=3 HEIGHT= 415 ><NOBR><div> <IMG SRC="23511990.jpg" border=0 width="529" height="409" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </NOBR></tD> </tR> </TABLE></div> <bR> <bR> <bR> <bR> </td> </tr></table></body>