Civil engineers for a better world
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 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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HY-8: POLYNOMIAL COEFFICIENTS Table 1. Polynomial Coefficients – Circular HY-8 Equation Inlet Configuration KE SR A BS C DIP EE F 1 Thin Edge Projecting 0.9 0.5 0.187321 0.56771 -0.156544 0.0447052 -0.00343602 8.96610E-05 2 Mitered to Conform to Slope 0.7 -0.7 0.107137 0.757789 -0.361462 0.1233932 -0.01606422 0.00076739 3 Square Edge with Headwall (Steel/Aluminum/Corrugated PE) 0.5 […]
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HEC-15 Section 6.1 – MANNING’S ROUGHNESS Manning’s roughness is a key parameter needed for determining the relationships between depth, velocity, and slope in a channel. However, for gravel and riprap linings, roughness has been shown to be a function of a variety of factors including flow depth, D50, D84, and friction slope, Sf. A partial […]
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Computed pipe diameters should be increased to a larger nominal dimension to avoid pressure flow. Standard English and metric nominal sizes used for storm drains are given in the table below. Nominal Pipe Diameters English metric inch ft mm 12 1.00 300 15 1.25 375 18 1.50 450 21 1.75 525 24 2.00 600 30 […]
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HEC-15 Section 3.1 & HDM Index 864.2 Shear Stress Equation The maximum shear stress is given by: τ = γ⋅Hn⋅S where: τ = shear stress in channel at maximum depth (N/m2 or psf) γ = unit weight of water Hn = depth of flow in channel (ft or m) S = channel bottom slope Table […]
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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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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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Author(s): Philip L. Thompson and Roger T. Kilgore Publisher: FHWA Year: 2006 Links: PDF Subjects: energy dissipator, culvert, channel, erosion, outlet velocity, hydraulic jump, internal dissipator, stilling basin, impact basin, riprap basin, riprap apron, drop structure, stilling well The purpose of this circular is to provide design information for analyzing and mitigating energy dissipation problems […]
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Author(s): McCuen RH, Johnson PA, Ragan RM Publisher: FHWA Year: 2002 Links: PDF Subjects: Hydrology, frequency analysis, peak discharge estimation, urban hydrology, hydrograph development, storage and channel routing, stormwater management, arid lands hydrology, wetland hydrology, snowmelt hydrology, GIS This document discusses the physical processes of the hydrologic cycle that are important to highway engineers. These […]
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