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HEC-15: Vegetative Lining Design

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CHAPTER 4: VEGETATIVE LINING AND BARE SOIL DESIGN Grass-lined channels have been widely used in roadway drainage systems for many years. They are easily constructed and maintained and work well in a variety of climates and soil conditions. Grass linings provide good erosion protection and can trap sediment and related contaminants in the channel section. […]

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HEC-15: Permissible Shear Stress

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HEC-15 Section 6.2 – PERMISSIBLE SHEAR STRESS Values for permissible shear stress for riprap and gravel linings are based on research conducted at laboratory facilities and in the field. The values presented here are judged to be conservative and appropriate for design use. Permissible shear stress is given by the following equation: τp = F*.(γs […]

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Side Slopes & Clear Recovery Zone

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Per the Caltrans Highway Design Manual Index 309.1(2), the roadside environment can and should be made as safe as practical. A clear recovery zone is an unobstructed, relatively flat (4:1 or flatter) or gently sloping area beyond the edge of the traveled way which affords the drivers of errant vehicles the opportunity to regain control. […]

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Trapezoidal Channel: Manning’s n

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Caltrans Highway Design Manual Commonly accepted values for Manning’s roughness coefficient are provided in Table 866.3A. The tabulated values take into account deterioration of the channel lining surface, distortion of the grade line due to unequal settlement, construction joints and normal surface irregularities. These average values should be modified to satisfy any foreseeable abnormal conditions […]

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HDS-4 Introduction To Highway Hydraulics

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Author(s): James D. Schall, Everett V. Richardson, and Johnny L. Morris Publisher: FHWA Year: 2008 Links: PDF Subjects: Hydrology, hydraulics, highway drainage, open channels, roadside ditches, pavement drainage, inlets, conduits, culverts, storm drains, energy dissipators Hydraulic Design Series No. 4 provides an introduction to highway hydraulics. Hydrologic techniques presented concentrate on methods suitable to small […]

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HEC-15 Design of Roadside Channels, 3rd Ed

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Author(s): Kilgore RT, Cotton GK Publisher: FHWA Year: 2005 Links: PDF Subjects: channel lining, channel stabilization, tractive force, resistance, permissible shear stress, vegetation, riprap, manufactured linings, RECP, gabions Flexible linings provide a means of stabilizing roadside channels. Flexible linings are able to conform to changes in channel shape while maintaining overall lining integrity. Long-term flexible […]

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