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<br />approved mat,,!rials to ml.nl.ml.ze erosion, to facilitate <br />maintenance, and to aesthetically blend with the adjacent <br />vegetation and soils. For sandy soils., a main channel is <br />required in a,::cordance with Section 5.4.2.6(b). For 100- <br />year runoff peaks of 20 cfs or less, t:rickle channel <br />requirements will be evaluated for e,ach case. Trickle <br />channels help preserve swales l:rossing residential <br />property,. <br /> <br />b. Right-Of-Way width - The minimum ROW \ddth shall include <br />freeboard and a 12-foot wide maintlmance access. <br /> <br />c. Flow Depth - The maximum design de,pth of flow (outside <br />the trickle channel area and main channel area for sandy <br />soils) for the 100-year flood shall be limited to 5.0 <br />feet in grass lined channels. <br /> <br />d. Side Slopes - Side slopes shall be 4 (he,rizontal) to 1 <br />(vertical) or flatter. Side slopl~s for channels with <br />100-year runoff of 20 cfs or less shall be 3H:1V or <br />flatter. <br /> <br />7. Grass Lining (Small Drainageway) <br /> <br />The grass lining for channels shall be in a.ccordance with the <br />USDCM, Section 2.3.2, "Major Drainage - Gl:'ass lined Channels <br />-Grass." <br /> <br />8. Erosion Control (Small Drainageway) <br /> <br />The requirements fer erosion control for gl:ass lined channels <br />shall be as defined in the USDCM, section 2.3.6, "Major <br />Drainage Erosion Ci;mtrol." The design e,f riprap and erosion <br />control devices shall be in accordance with sections 10.1 and <br />10.2 of these Crit,,!ria. <br /> <br />9. Hydraulic Information (Small Drainageway) <br /> <br />Calculations of the capacity, velocity, and Froude Numbers <br />shall be submitted with the Final Drainage Report. <br /> <br />5.5.3 <br /> <br />Concrete Lined Channels (Small Draiu9'.lnfAYl <br /> <br />The criteria for the design and construction of concrete lined <br />channels is presented bEllow: <br /> <br />1. Hydraulics (Small Drainageway) <br /> <br />a. Freeboard - Adl~quate channel freeboard above the designed <br />water surface shall be provided and shall not be less <br />than determinE~d by Equation 5.3. Fre.eboard shall be in <br />addition to super elevation, standin~J .raves, and/or other <br />water surface disturbances. These special situations <br />should be addressed in the Final Dr.ai:rlage Report. <br /> <br />5 - 14 <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />