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<br /> -9- <br /> mitigate their impact on water quality through the <br /> use of approved control strategies to control <br /> sediment, neutralize contaminants, and dissipate <br /> energy by the use of multiple smaller outlets <br /> whenever practical, by locating discharges to <br /> maximize overland flow, and by any other strategies <br /> which will accomplish the objectives defined and <br /> discussed herein. <br /> Sec. 6. Velocity attenuation and surface drainage <br /> channels. <br /> A. All drainage channels that are to be <br /> constructed or that are to be altered for drainage <br /> purposes shall conform to the criteria of this <br /> section. <br /> B. Surface drainage channels shall be designed to <br /> minimize potential erosion and to increase the <br /> bottom width to flow depth ratio: <br /> 1. Channel cross-sections shall be <br /> trapezoidal in configuration. <br /> 2. Side slopes of channels shall be no <br /> steeper than four (4) horizontal to one <br /> (1) vertical. <br /> 3. For a six-month design storm assuming wet <br /> antecedent conditions, channel bottom flow <br /> depth shall not exceed four (4) inches and <br /> design flow velocity shall not exceed two <br /> and one-half (2 1/2) feet per second. <br /> 4. All constructed and altered drainage <br /> channels shall be stabilized and vegetated <br /> as soon as practicable after final <br /> grading. <br /> 5. The Director may allow exceptions to the <br /> design flow velocities or depths in the <br /> following situations in conformance with <br /> the purpose of the previous section of <br /> this ordinance: <br /> a. On lands with greater than fi fteen (15) <br /> percent slope, provided that the <br /> design flow velocity shall never be <br /> greater than three (3) feet per second. <br /> b. In limited transitional channel <br /> sections (such as culverts, culvert <br /> entries and exits, drop sections, sharp <br /> bends, and water quality basin <br /> entries). <br /> c. Channelization of the San Marcos and <br /> Blanco Rivers and any tributary of the <br /> San Marcos River within the SMRC shall <br /> be prohibited. <br /> Sec. 7. Ecological preservation. <br /> A. All the requirements, standards, and processes <br /> concerning landscaping, buffering, and the <br /> preservation of natural vegetation as detailed in <br /> Chapter 14 1/2, Landscape and Buffering Ordinance, <br /> of the City Code shall be followed within the SMRC. <br />