page_title: Open channel spillway
section_title: Flow Rates
hierarchical_section_title: Open channel spillway / Flow Rates
caption_attribution_description: English: Straight Inlet
context_page_description: Open channel spillways are dam spillways that utilize the principles of open-channel flow to convey impounded water in order to prevent dam failure. They can function as principal spillways, emergency spillways, or both. They can be located on the dam itself or on a natural grade in the vicinity of the dam.
context_section_description: Different agencies have different methods and formulas for quantifying flows and conveyance capacities for chute spillways. The Natural Resources Conservation Service (NRCS) produced handbooks on dam design. In National Engineering Handbook, Section 14, Chute Spillways (NEH14), flow equations are given for straight inlets and box inlets.
  NEH14 provides the following discharge-head relationship for straight inlets of chute spillways, which is given by the flow equation for a weir:
  Q = 3.1W[H + vₐ²/2g]3/2 = 3.1Hₑ3/2
  Where:
  Q = discharge of inlet (ft³/s)
  W = width of the chute or inlet (ft)
  H = depth of flow over the crest (or floor) of the inlet (ft)
  Hₑ = specific energy head in reference to the crest of the inlet, or the head over the crest of the inlet (ft)
  vₐ = mean velocity of approach at which the depth H is measured (ft/s)
  g = 32.16 ft/s²
caption: Straight Inlet
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