These equations are referred to as slope-area methods on the basis that they utilises simple relationships between the discharge in a river to the energy gradient, flow cross-sectional area and hydraulic roughness. The simplest model available for computing flood levels and flow velocities is the use of empirical formulae such as the Chezy Equation and the Manning's Equation.
Localised energy losses due to junction and inlet pits are computed in a similar manner using standard coefficients derived from extensive laboratory tests of these structures. The energy loss attributed to pipe friction is best calculated by the Darcy-Weisbach Equation. In closed conduit flow conditions, calculation of energy losses within the flow conveyance system is most commonly based on applying energy loss factors to the velocity head (v2/2g).
Frequency of surcharge of underground drainage systems.The design process is commonly a series of iterations involving modifying the various hydraulic structures such that the resulting HGL complies with the design standards specified. In closed conduit flow conveyance systems, flow conditions can be pressurised and water rises to the HGL level at junction pits. In the case of open channel flow, the HGL generally coincides with the water surface. The HGL is often used to determine the location of the hydrostatic head along the water conveyance system. In all cases, hydraulic calculations are aimed at computing energy losses in the flow conveyance system such that the hydraulic grade line (HGL) of the system can be established. Hydraulic procedures are required to compute flow characteristics in closed conduits and open channels during the passage of a runoff hydrograph. Hydraulic design of waterways and associated hydraulic structures are necessary to safely and efficiently convey stormwater runoff generated from main roads and highways and to provide crossings of these roads over creeks, floodways and rivers.
Overview of Hydraulic Procedures 1.1 General 1.5 One-Dimensional Unsteady Flow Modelsġ.
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