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  § 3.2.0. PERMISSIBLE SPREAD OF WATER  


Latest version.
  • The flow of water in gutters of typical streets during the 25-year storm shall be contained below the top of curb and shall maintain the clear width requirements listed in Table 3-1. The flow of water shall be limited to a maximum of 6″ above the top of crown during the 100-year storm event and must be contained within the defined right-of-way and easements. These clear widths at the crown of the roadway or at the high point on a divided roadway are necessary to provide access for vehicles in the event of an emergency.

    Equation 3-1 (from equations presented in HEC-22, FHWA-NHI-10-009, modified to solve for depth rather than flow or spread) may be used to determine the depth of gutter flow for a specific street width and flow spread.

    y = 4H(S/W) - 4H(S /W ) (Eq. 3-1)

    Where,

    y = Water depth in the gutter (feet) (limited to 0.5ft)

    W = Street width (feet)

    H = Crown height (feet)

    S = Spread on one side of street (feet)