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<br />Page 16 <br /> <br />B. Hydraulic Criteria: The preliminary and final design reports shall be <br />consistent with the hydraulic properties and behavior specified in this <br />section and conform with the USDCM. <br /> <br />1) Open Channels are subdivided into two classes: major channels and <br />minor channels. Major channels include all drainageways and all <br />other channels which convey major storm discharges greater than 100 <br />cfs or any channel which has a designated flood plain on the City's <br />Official Flood Hazard Map. All other channels are minor channels. <br /> <br />a) Grass Lined: Grass lined channels are preferred and shall be <br />used unless physical restraints make their use infeasible. <br />Limiting criteria varies with size, capacity, soils, type of <br />grass, irrigation, neighborhood, and other factors. Any design, <br />however, which has characteristics outside of the limits of <br />Tables V and VI shall receive special scrutiny in the review. <br />Trees and shrubbery should not be permitted to grow in major <br />channels. <br /> <br />b) Concrete Lined Channels: Concrete lined channels are to be <br />avoided normally. For criteria for concrete lined channels <br />refer to USDCM. Concrete lined channels must be used if the <br />Froude Number exceeds 0.8. <br /> <br />c) Rock lined channels: Rip rap lined channels will be permitted <br />only in areas of existing development where available right-of- <br />way prohibits the use of grass lined channels. Riprap lined <br />channels shall be designed to have a Froude No. less than 0.8 <br />and be designed in accordance with USDCM (Volume 2, Maj or <br />Drainage Section 5 - Riprap, as revised). <br /> <br />d) Trickle Channels: A trickle channel shall usually be provided <br />in major channels to provide acceptable flow characteristics at <br />low flows. Trickle channels shall be lined with grouted rip <br />rap (preferred) or concrete. <br /> <br />2) Culverts: All culverts shall be designed in accordance with the <br />procedures in USDCM. Figures 7 to 11 are most frequently used ill <br />culvert design and are included for ease of reference. Maximum <br />headwater depth at inlets shall be one and one half times the pipe <br />diameter (HW = 1.5 D). <br /> <br />Outlet velocities of all culverts must be checked. When the outlet <br />velocity exceeds the maximum permissible channel velocity listed in <br />Table V. or Table VI, energy dissipators shall be provided to mini- <br />mize potential erosion at outlet. <br /> <br />3) Energy Dissipators: Typical acceptable energy dissipators are shown <br />in USDCM. Design of energy dissipators, where required, shall be in <br />accordance with USDCM or CDOH Erosion Control Manual. <br />