(Ft.) 468 General Criteria Applicable to All Purposes: A waterway or outlet having an Capacity. The maximum capacity of the lining of concrete, stone, synthetic turf waterway flowing at designed depth shall not reinforcement fabrics, or other permanent exceed 200 ft3/s. The minimum capacity shall material. be adequate to carry the peak rate of runoff from a 10-year, 24-hour frequency storm. Velocity shall be computed by using Manning’s Formula with a coefficient of roughness as “n” This practice may be applied as part of a follows: resource management system to support one or more of the following purposes: Provide for safe conveyance of runoff from Lining Value “n” conservation structures or other water Concrete concentrations without causing erosion or flooding Trowel 0.011– 0.015 finish.................. Stabilize existing and prevent future gully erosion Float finish……............. 0.013 - 0.016 Protect and improve water quality 0.016 0.025 – 0.020 0.025 – This practice applies if the following or similar conditions exist: 1/ Riprap - (Angular n = 0.047(D50 Concentrated runoff, grades, wetness, Rock) S)0.147 prolonged base flow, seepage, or piping is Synthetic Turf Manufacturer’s such that a lining is needed to control Reinforcement Fabrics recommendations erosion and Grid Pavers Use by people or animals precludes vegetation as suitable cover. Limited space is available for design width, 1/ Applies on slopes between 2 and 40% with which requires higher velocities and lining. a rock mantle thickness of 2 x D50 where: are highly erosive or other soil or climatic conditions preclude using vegetation only. D50 = median rock diameter (in.), S = lined section slope (ft./ft.) (.02 S 0.4) ≤ ≤ Figure 2. Maximum velocity versus depth of flow for concrete-lined channels
(Ft.) 468 A waterway or outlet having an lining of concrete, stone, synthetic turf reinforcement fabrics, or other permanent material. This practice may be applied as part of a resource management system to support one or more of the following purposes: Provide for safe conveyance of runoff from conservation structures or other water concentrations without causing erosion or flooding Stabilize existing and prevent future gully erosion Protect and improve water quality This practice applies if the following or similar conditions exist: Concentrated runoff, grades, wetness, prolonged base flow, seepage, or piping is such that a lining is needed to control erosion Use by people or animals precludes vegetation as suitable cover. Limited space is available for design width, which requires higher velocities and lining. are highly erosive or other soil or climatic conditions preclude using vegetation only. General Criteria Applicable to All Purposes: Capacity. The maximum capacity of the waterway flowing at designed depth shall not exceed 200 ft3/s. The minimum capacity shall be adequate to carry the peak rate of runoff from a 10-year, 24-hour frequency storm. Velocity shall be computed by using Manning’s Formula with a coefficient of roughness “n” as follows: Lining “n” Value Concrete Trowel finish.................. 0.011– 0.015 Float finish……............. 0.013 - 0.016 0.016 – 0.025 0.020 – 0.025 1/ Riprap - (Angular Rock) n = 0.047(D50 S)0.147 Synthetic Turf Reinforcement Fabrics and Grid Pavers Manufacturer’s recommendations 1/ Applies on slopes between 2 and 40% with a rock mantle thickness of 2 x D50 where: D50 = median rock diameter (in.), S = lined section slope (ft./ft.) (.02 ≤ S ≤ 0.4) Figure 2. Maximum velocity versus depth of flow for concrete-lined channels